Frequently Asked Questions - All FAQs

Keyboard “Start/Stop” may be deactivated. A single spout gross packer can take advantage of the front panel keyboard “Start/Stop” switches. However, if the 4693 controller is used as a Dual controller (operating two spouts simultaneously) the front panel switches are disabled and either push buttons or some other hard input must be used to start and stop each spout.

A Net Weigh scale controller can use external push buttons, or may use the front panel keyboard for starting and stopping production filling. The keyboard start is operated by pressing “Start” key, followed by either the numeric keyboard key #1 (starts scale #1), key #2 (starts scale #2), or key #3 (starts both scales #1 & #2). Stopping production works in the same way.

External Start/Stop switches may be functioning properly, but internally the input receiving the signal from the switch may have failed. To verify, reference the user’s manual section on configuration, and look for Test Routines. A test is available for visually confirming that each input and output in the controller are functioning properly. If the input is confirmed as bad, replace the I/O card.

Bad input device; push button, limit switch, etc. To drive the Start or Stop input, a “hot” wire from the controller is connected to one side of a Normally Open contact on the external switch. The other side of this contact is then connected to the appropriate input, providing a closed circuit and energy to the input when the contact closes. Verify continuity of this contact in both the open and closed states.

Display screen must be in “run filler” mode. As a safety factor, the 4693 & 5297 fill controls do not allow filling in any other menu or screen. This allows the operator to simply press Esc on the front panel keyboard, and disable filling on the machinery. If a fill is currently in progress, hitting Esc will allow that fill to complete, discharge, and then the filling process will stop.

Display screen must show “Ready” below the last fill weight. There are a number of phases during the fill process, including discharge of the filled weigh bucket or bag. Look below the current/final weight displayed in the “run filler” screen. A status line displays current status of the filler, such as “Ready”, “Bulk”, “Discharge Inhibit”, etc.

For gross packers, there are four possible sources of delay; settling time, TARE timer, placer dwell time, refill valve time. Net weigh scales have three possible sources; settling time, TARE timer, and hopper discharge time. Other fillers, such as bulk bag filler controls, may have a number of timer functions that can impose delays at the beginning of a fill. See user’s manual, or contact Thompson Scale for more information.

Settling time is an internal timer that allows the weigh bucket or bag just placed onto the fill spout to come to rest before the filler controller captures a TARE weight value. The typical setting for this value is 0.5 second. Once a fill is started, the controller waits for the Settling Time, then takes a 0.5 second average of current weight on the scale to calculate the TARE, then begins the fill. Refer to your user’s manual for information on how to find and set this value.

Fills between TARE can be adjusted to minimize wait time at the beginning of each fill. A TARE takes 0.5 second to complete, and is conducted at the beginning of each fill. Setting this variable to a value greater than one (1) will cause the controller to re-use the TARE value used in the first fill, then update the TARE based on the variable value selected.

Manual TARE is also available for some programs. This setting is found within the configuration menu. See the user’s manual for more information.

Placer Dwell Time is a value used on the gross packer controller that operates in conjunction with an automatic bag placing machine. When the bag placer loads a bag onto the fill spout, a short period of time elapses before the placer releases the bag and retracts from the packer. This Dwell time must be taken into consideration, or would interfere with taking a valid TARE. If a bag placer is NOT being used, this value should be set to 0.0. Placer Dwell Time is found in Main Menu #4.

Air packers use a slide gate or butterfly valve at the top of the product chamber to isolate the chamber prior to pressurization by the low pressure blower. At the end of each fill, this valve is cycled open to re-charge the chamber with product. The amount of time required to do this is usually very short. Check this value to ensure it is set to the optimum time, allow the chamber to fill adequately, but without causing undue delay. Refill Timer is found within each product set-up, along with Target Weight.

Net weigh scales have a timer setting for the discharge of product from the weigh hopper. This value should be set to provide adequate time for all product to leave the weigh hopper, but short enough to avoid causing delay before the next fill can begin.

It is difficult at best to get an exact match between any two scales. A filling system, especially a valve packer (air, impeller, auger) is a dynamic filler, taking weight data while product and entrained air are still in-motion within the bag and filler. A number of factors play a role in accuracy of the filler, when compared to a static scale:

• Changes in product bulk density
• Bag size
• Amount of entrained air
• Amount of settling time at the end of each fill
• Mechanical characteristics of the filler itself
• Degree of isolation and accuracy of the mechanical filler

Determine repeatability of the filler system. Placing a test weight onto the scale, and then removing the test weight should first display the test weight value, to within a few increments, and then display zero when the weight is removed. If your scale shows inaccurate or non-repeatable weights, or the weight value slowly “creeps” up to the test weight or back to zero, there may be mechanical issues with the equipment. The faster and more reliable the scale and filler, the better performance you will receive.

Use Offset Compensation to reduce scale differences. A feature within the filler controller’s configuration menu allows the user to adjust the value shown for the final weight. If, for example, a filled bag weighs 25 lb. at the filler, but weighs only 23 lb. on a static scale, Offset Compensation can be invoked to increase the actual bag’s final weight by 2 lb. while still displaying a final weight of 25 lb. This is a global setting that will induce compensation in each product recipe stored in the controller.

Uncontrollable product flow rate is the leading cause of erratic final weights. If the flow of the product changes dramatically during the fill, it is virtually impossible for the filler controller to detect or predict the correct cut-off point. Flow rate is typically affected by the amount of air induced and ability of the butterfly valve on top of the chamber to maintain proper pressure during the fill. Try reducing/increase blower pressure and confirm the butterfly valve is working properly. Impeller packers may cavitate if run too fast, or blades may be worn. Auger packers may be running out of round, or too quickly to provide reliable cut-off at the end of the fill.

The cut-off device may not be working properly. An erratically operating pinch tube cut-off air cylinder, or a feeder for a net weigh scale can destroy accuracy very quickly. Make sure that the cut-off reacts exactly the same from fill to fill, and does not hesitate or bind when closing.

Valve packer machinery is very sensitive to bag size. If you suspect that your bags are under-sized for the target weight, reduce the target weight by 10 lb. and run AT LEAST 10 fills. If bag weights are consistent at this lower weight, but not at the actual target, the bags are probably too small.

The filler controller monitors and stores TARE values to use as reference on each fill. If the TARE on one fill is more than 3% different than the previous fill, the controller will detect this difference, assume that excess product is in the bag or weigh hopper, and will use the TARE from the previous fill. When this occurs, the controller displays “TARE FAULT” on the line directly below the weight. If this error occurs three (3) times in a row, a new TARE will be established on the 4th fill.

If you are confident that the TARE Fault is not caused by product existing in the bag or net weigh scale, then it must be assumed that the mechanical portion of the filler is not returning to the same starting point as the last fill. This can be attributed to mechanical binds or damage to the scale’s flexures or load cell. Find the source of the bind or damage and repair.

The Thompson Scale line of filler controllers has a very advanced algorithm for calculating the cut-off values for Bulk and Dribble (if used) and Preact. This works extremely well on free-flowing and stable products with consistent bulk densities. The filler first runs a sample of product at both Bulk and Dribble (if used) flow, and then immediately calculates the final cut-off values. The final weight is taken at the end of the fill, and compared to the Target. Adjustments are made automatically and tracked EVERY fill.

For some applications, it is more efficient and more accurate to run manual set points. The operator manually sets Bulk, Dribble, and Preact values, and then selects either automatic tracking or no tracking. The default setting for the filler controller is Automatic Set Points. To change, enter into the configuration menu and select Manual Set Points. Reference your user’s manual for entering into and changing configuration settings.

Preact is loosely defined as the amount of product that falls into the container (bag or hopper) after the product feed has been shut off. For example; if a column of product is flowing from the feeder, and the container is located 6″ below the container, when product flow is stopped, a column of material 6″ long will still be falling into the container.

In most cases, this column of product in suspension between the feeder and the scale needs to be accounted for when setting set points. Let’s say that the column of product weighs ½ lb. If the Target weight is 50 lb., then the final set point value should be set to 49.50 lb. and Preact set to 0.50 lb. When the feeder is stopped at 49.50 lb., the additional 0.5 lb. of product in suspension settles into the bag or hopper, bringing the total weight up to 50 lb. This is called Positive Preact.

Sometimes the force of this product column, falling against the bag or hopper, is strong enough to cause a Negative Preact. This means that once the product column stops and the force of the column is relieved, the weight in the bag or hopper ends up being less. For example, on a 50 lb. Target, the final set point is set to 50. lb., and a Negative Preact of 0.50 lb. is entered. Once the controller detects that weight is at 50 lb., it knows that it needs to continue filling until it detects 50.50 lb. Once filling is stopped, and the pressure from the product column is relieved, the final weight settles at 50.00 lb.

Front panel access is provided for making minor adjustments to the Preact value, when running in the Manual set point mode. This allows the operator to quickly tune the final fill weight without leaving the “Run Filler” screen.

• Not enough test weight on scale.
  The filler controller requires at least 10% of the load cell’s capacity to be used as a test weight. For example, a 500 lb. Load cell would require a 50 lb. test weight The controller’s calibrated operating range is 2 times the size of the test weight. If the unit is calibrated with 25 lbs., the controller can only weigh up to a 50 lb. product weight, and then will display an “Over Scale” error.
  
  
• Confirm power supply is working properly
  All DC voltages are generated by the 472, and are used to power the 474 Load Cell Digitizer card. If any LED on the front faceplate of the #472 card is not lit, remove power from the controller, then remove the 472 card and replace the failed fuse with one of the on-board spares
  
  
• Check for 10 VDC output to load cell
  Using a digital electrical meter set to VDC, and with the scale controller on, place the leads on the 474 Load Cell Digitizer card terminals 1 and 5. The output should be 10 VDC, plus or minus less than 1%. If the voltage is lower or higher than this value, it may indicate a defective Load Cell Digitizer card or Power Supply card.
  
  
• Check Load Cell
  Using a digital electrical meter set to mV (millivolts), and with the scale controller on, place the leads on the #474 Load Cell Digitizer card terminals 3 and 4. A load cell rated at 2mV/V (total output of 20mV since we excite the load cell with 10 VDC) should have a reading 2 to 12 mV with nothing on the scale. The mV reading should increase by about 2 to 4 mV when the test weight is applied.

Changes were made to the recipe, BUT the recipe was not loaded.

Check Sample Rate and Filter Frequency settings: Confirm these settings are Sample rate = 100, Filter Frequency = 5

• For Gross Auger Packers, check the screw.
  If the auger screw is out of round, it can induce a large enough weight for the Filler to consider this an actual fill
• For Gross Air or Impeller Packers, check scale and isolation bracket operation.
  Go to Check Cal Menu screen and press Z key. This will zero the weight reading. Press down and up on the scale, and confirm the weight reading goes up and down and quickly returns back to Zero reading. Now place test weight on the scale and confirm weight reading is close to test weight value. Press down and up on the scale, and confirm the weight reading goes up and down and quickly returns back to Test weight reading. Now place a bag on the spout and manually engage and disengage the Cut Off Gate (cylinder that clamps the fill tube). The weight reading should not increase, or if it does so, only slightly.

This particular screen re-paints the screen in such a manner as to produce what looks like the screen is pulsing, but it is an inherent feature of the screen and cannot be fixed.

The 4693 controller is provided with a switching power supply input for source 110 VAC power. This power supply does an excellent job of filtering “noise” and voltage/frequency variations in the source 110 power. However, it cannot filter out everything. It is possible that your source 110 VAC supply to the controller is subject to surges, spikes, sags, etc. that are more prominent than normal. Check the source power, and possibly install a line conditioner to see if this eliminates the problem. Call Thompson Scale for a recommendation on line conditioners.

EMI/RFI from Inductive loads. A device such as a solenoid valve coil or relay coil, or transformer style pilot light, are all considered as inductive devices. When the coil of this device is energized via one of the filler controller’ outputs, a magnetic field is created around this coil. When the device is de-energized, this field collapses, causing a momentary current inrush to occur. This inrush current can feed back to the output that originally turned on the device, and in extreme cases, can cause the controller to reset. Install a snubber (quench arc) across the COIL of the device. This should eliminate the problem. Contact Thompson Scale for recommendations on snubbers and their proper installation.

Static discharge is another possible source of this problem. Make sure that a proper ground has been attached to the supply hopper, filler frame, and controller ground. Product in-motion from the process location to the filler can pick up static, but cannot find a path to discharge the energy if a sufficient ground is not provided.

Password is required, but either don’t know it or don’t have one. Press front panel ESC key until display shows Main Menu. Now select item 5 (Select/Edit Product), then 3 (Edit Password). When asked for password, type in the word “scale”. The next prompt will be for entry of a new password. If desired, enter a new password. To disable password protection, press the Space Bar once, then press Enter.

The keyboard provided on the 4693 controller is read by the #476 card located at the bottom inside of the controller door. In the bottom left corner of the 476 card are two (2) red LED’s. One is dedicated to the processor chip on this card, and blinks on/off like a heartbeat to show proper operation of the processor. The other LED provides a visual indication that a key press on the keyboard is properly read. Press the suspect key(s) while watching this LED. If the LED does not blink each time the key is pressed, the key has most likely failed. If the LED does blink, but the controller does not properly respond, the 476 card may be defective. Contact Thompson Scale for further assistance and to purchase replacement parts required.

The LCD display module is composed of several components, including a conductive rubberized strip that lies between the LCD circuit board and the LCD glass. If corrosion or product contamination gets into this area, it can cause a loss of continuity between the strip and glass, presenting a blank (off state) line on the display. Due to the precise orientation of the strip to glass, it is not practical to disassemble and clean this area since proper re-assembly is extremely difficult.

The LCD should be replaced, and care should be taken to ensure product dusts or gasses do not enter the enclosure.

The LCD graphics module uses a fluorescent backlight provided with an adjustment for contrast. Over time, the backlight may loose some efficiency and require adjustment. Open the controller door and locate the #476 card at the bottom of the door. In the upper left corner of the 476 card is a daughter card with a connection of two white wires to the display’s back light. Just to the right of this daughter card is a small blue potentiometer with a white center. This is the contrast adjustment. Adjust as necessary. If this does not resolve the problem, contact Thompson Scale for further assistance.

Not enough test weight on scale.
It is recommended that a test weight of at least 50% of your heaviest product run across this scale should be used to calibrate the scale. A weight less than this will not create enough of a difference (span) between no test weight and the applied test weight for the controller to recognize as a valid weight. Keep in mind that the controller’s calibrated operating range is 2 times the size of the test weight. If the unit is calibrated with 5 kg., the controller can only weigh up to a 10 kg. product weight, and then will display an “Over Scale” error.

Too much test weight on scale.
The full-load capacity of the scale’s load cell should NOT be exceeded. A test weight that places the load cell into overload will not produce accurate weight readings of your product, and will most likely cause damage to the load cell. Check the capacity of your system before selecting a test weight.

Load cell damage to scale.
It is possible for a load cell to receive two types of damage; mechanical overload and shock overload. Mechanical overload, such as applying 20 kg. to a 10 kg. scale, simply distorts the elements within the load cell to a point where they do not return to their previous state, and calibration cannot be done reliably or at all. Shock overload, such as dropping a 5 kg. bag onto the same scale. The 5 kg weight itself is not enough to overload the scale, but the acceleration force of the weight is. Calibration with a damaged load cell will present drift, erratic weights, non-repeatable calibration checks, etc. Load cell replacement is recommended.

Not enough test weight on scale.
Check the capacity of your checkweigher first. Use a test weight that is at least 50% of your largest product’s weight for calibration. The controller’s calibrated operating range is 2 times the size of the test weight. If the unit is calibrated with 5 kg., the controller can only weigh up to a 10 kg. product weight, and then will display an “Over Scale” error.

Confirm power supply is working properly.
All DC voltages are generated by the 472, and are used to power the 474 Load Cell Digitizer card. If any LED on the front face plate of the #472 card is not lit, remove power from the controller, then remove the 472 card and replace the failed fuse with one of the on-board spares.

Check for 10 VDC output to load cell.
Using a digital electrical meter set to VDC, and with the scale controller on, place the leads on the 474 Load Cell Digitizer card terminals 1 and 5. The output should be 10 VDC, plus or minus less than 1%. If the voltage is lower or higher than this value, it may indicate a defective Load Cell Digitizer card or Power Supply card.

Check Load Cell.
Using a digital electrical meter set to mV (millivolts), and with the scale controller on, place the leads on the #474 Load Cell Digitizer card terminals 3 and 4. A load cell rated at 2mV/V (total output of 20mV since we excite the load cell with 10 VDC) should have a reading 2 to 12 mV with nothing on the scale (except the weigh station conveyor). The mV reading should increase by about 2 to 4 mV when the test weight is applied.

A load cell rated at 3mV/V (total output of 30mV since we excite the load cell with 10 VDC) should have a reading of 3 to 20 mV with nothing on the scale (except the weigh station conveyor). The mV reading should increase by about 3 to 5 mV when the test weight is applied.

Filter Frequency in the configuration menu has been set to zero (0). Enter the configuration menu, as described in the manual, and confirm this setting. Normally it should be set to 5.

Number of system photo-eyes set incorrectly. Enter the configuration menu, select item #8 (Get Next Menu), then select “P) Photo-Eye Configuration”. This setting should be equal to the actual number of photo-eyes connected to inputs within the controller. If there are no photo-eyes associated with your checkweigher, this value should be zero (0). If there are no photo-eyes, but this value is set to 1 or 2, the checkweigher program is awaiting an input from the photo-eye to trigger termination of the weighment, and will never display a weight value.

Checkweigher frame installation is critical to proper and repeatable weights. The product entering and leaving the conveyor should be smooth as possible. In-feed and discharge conveyors surrounding the checkweigher should be at the same level and speed. Gaps between conveyors should be kept to a minimum, since too large a gap will allow the product to “nose dive” into the checkweigher, causing product instability.

Support structure for the checkweigher must be isolated and stable. A structure tied to in-feed or out-feed/reject conveyors will induce low-frequency vibrations into the weigh station scale, affecting weight accuracies.

Conveyor belt tension on the Sonic 350, and chain tension on the TSC 350 are very important. Running the belt too tight will cause excessive loading on the conveyor rollers and excessive friction of the belt against the slider bed. The belt should be loose enough to lift at the center between the head and tail rolls, and you should be able to slide your hand between the belt and slider bed, touching the middle of the slider bed. Another way to adjust this tension is to place your heaviest package on the weigh station conveyor and then start the conveyor. The belt needs to be only tight enough to start without slippage of the belt.

Make sure motor cables on the Sonic 350 Checkweigher are not drawn tight, and are anchored properly. Tight or moving cables will cause inaccuracies.

The Sonic 350 conveyor roller bearings must be properly maintained to provide accurate and repeatable weights. If the bearings are worn or have partially failed, the drag and mechanical “noise” generated by the bearing will affect weights.

The head and tail rolls on the weigh station are precision balanced prior to installation. This balance allows the rolls to turn at any speed without generating low-frequency vibrations (kind of like an out-of-balance tire on your car). If the shaft of the roller becomes bent, due to mechanical impact or over-tightened belt, the roller will generate low-frequency “noise” and affect the accuracy of the scale.

The Sonic 350 scale conveyor length and speed have been specifically configured for your application. These two factors, along with your product length, provide Thompson Scale with enough information to formulate the highest possible production rates at the right speed, and provide enough weighment time for each package. However, if the conveyor speed is increased or a new longer package is introduced into production, sufficient weighment time may not be possible. Contact Thompson Scale with information on; maximum product length, conveyor length, and conveyor speed. We will quickly calculate minimum weighment times, and make recommendations on possible solutions to your application problem.

Along with the minimum weigh time, described above, it is also very important that only one product is on the scale at one time. For systems without an exit-end photo-eye (called our Early Weight Terminate photo-eye option), the leading edge of the package must be about 1/4 of its length off the weigh station before we terminate the weighment cycle on that package If the weighment cycle of the first package is not completed prior to entry of another package, weight from the 2nd package will influence the final weight of the first. Make sure that packages are properly spaced.

Load cell damage will also affect weight. The load cell below the weigh station conveyor or weigh table should provide reliable, accurate, and linear weights across the entire weighing surface. Place the controller into the Calibration Check mode, and then place a test weight at the center of the conveyor or weigh table. Record the displayed weight, then move the test weight to each corner of the conveyor or weigh table. The values in each corner should be +/- 2 increments of the center weight value. If one or more corners are out of tolerance, then the load cell or weigh table or conveyor may require adjustment. Contact Thompson Scale to discuss your readings and possible solutions.

The checkweigher controller monitors the load cell output as its only source of weight data. If excessive vibration causes high weight readings to occur while the checkweigher is trying to take a weighment, over-weight values will be generated.

It is possible to enter a TARE or container value in the product setup for each product you run. Make sure that the TARE on the static scale is the same as that of the product setup.

Inaccurate calibration or loss of valid calibration. The checkweigher controller uses values defined in calibration to determine product weights crossing the scale. If this calibration was performed improperly, such as using a 2 kg. weight but entering a 5 lb. test weight value in the controller, the package weights will not be calculated properly. If a significant change occurs to the scale’s load cell, such as overload damage, hitting the weigh station conveyor with a forklift, removing the weigh station conveyor and then replacing, interference from motor or photo-eye connections, it will affect calibration.

Operating Zero can be affected by removing built-up product on the weigh station conveyor and scale. The operating zero is maintained by an automatic zero tracking program within the checkweigher’s program. However, this feature can only zero out a maximum of ½% of the load cell capacity at one time. If more than ½% is added or removed at one time, it will be necessary to enter into the Calibration Check screen and manually zero the scale. If this is not done, it may take several package weights to fully re-zero the scale.

Differences in the static scale and the checkweigher’s scale. It is quite possible that the static scale and checkweigher just differ in what is displayed on a package weight. This difference is almost always a small amount, such as 1 or 2 increments different. The static scale may not have the same accuracy or resolution as the checkweigher. If this is the case, it is dangerous to try and compare an accurate scale with one having less accuracy. The static scale should have at least the same accuracy and display resolution as the checkweigher, and best case, should be about 2 times as accurate and the checkweigher.

Weighment cycle too short. A package must be on the checkweigher for a minimum period of time to generate an accurate and repeatable weight. Run the package across the scale 10 times, writing down each weight. Are the weights the same, +/-0.5%? If not, most likely there is not enough time for the checkweigher to properly weigh the package. Contact Thompson Scale for further assistance.

It is possible to enter a TARE or container value in the product setup for each product you run. Make sure that the TARE on the static scale is the same as that of the product setup.

Inaccurate calibration or loss of valid calibration. The checkweigher controller uses values defined in calibration to determine product weights crossing the scale. If this calibration was performed improperly, such as using a 2 kg. weight but entering a 5 lb. test weight value in the controller, the package weights will not be calculated properly. If a significant change occurs to the scale’s load cell, such as overload damage, impacting the scale conveyor, removing the conveyor and then replacing incorrectly, interference from motor or photo-eye connections, it will affect calibration.

Operating Zero can be affected by removing built-up product on the scale conveyor and scale. The operating zero is maintained by an automatic zero tracking program within the checkweigher’s program. However, this feature can only zero out a maximum of ½% of the load cell capacity at one time. If more than ½% is added or removed at one time, it will be necessary to enter into the Calibration Check screen and manually zero the scale. If this is not done, it may take several package weights to fully re-zero the scale.

Differences in the static scale and the checkweigher’s scale. It is quite possible that the static scale and checkweigher just differ in what is displayed on a package weight. This difference is almost always a small amount, such as 1 or 2 increments different. The static scale may not have the same accuracy or resolution as the checkweigher. If this is the case, it is dangerous to try and compare an accurate scale with one having less accuracy. The static scale should have at least the same accuracy and display resolution as the checkweigher, and best case, should be about 2 times as accurate and the checkweigher.

Chain tension is critical to proper weighing. If the tension is too tight, resistance between the chain tension and weigh table will not allow a product to be properly weighed. Too loose chain tension creates problems with consistent transportation of the chain through the chain path, and may cause the drive sprockets to skip teeth.

The flat-top Nylatron© chain used on the TSC 350 has flat side plates that can become chipped, cracked, and worn. Inspect the chain to make sure that both sides and bottom of chain are smooth and defect-free. Replace damaged links.

Proper alignment of the in-feed, weigh table, and out-feed chain guides is critical to accurate and repeatable weighing. Using a taught string or rigid straight edge, confirm that the in-feed and out-feed guides are straight and parallel to the weigh table.

In-feed and out-feed chain guides must be at the same height as the weigh table. Using something similar to a business card, slide the edge of the card along the in-feed guide, and across the weigh table. The card should slide smoothly across these surfaces. If bumps or drops are felt, level the guide

The TSC 350 is provided with replaceable end caps on the in-feed and out-feed chain guides. This is the highest wear part of the chain path, and once work, the end caps can be a source of mechanical noise and chain surge.

Some TSC 350 Checkweighers are provided with a Early Weight Terminate photo-eye at the discharge end of the weigh table. This photo-eye must be aligned to catch the leading edge of the product at the instant the product is transferring from the weigh table to the out-feed guides. Adjust the photo-eye as necessary.

This LED is provided as a “heartbeat” indicator. As long as the LED blinks on and off at a steady pace, the controller’s CPU is operating properly. If this LED is continuously ON or OFF, consult the factory for more in-depth trouble shooting assistance.

If an updated program EPROM was installed into your controller it is possible that a feature has been moved or modified as part of the updated program. Contact us for more information on your specific program.

Password is required, but either don’t know it or don’t have one. Press front panel ESC key until display shows Main Menu. Now select item 5 (Select/Edit Product), then 3 (Edit Password). When asked for password, type in the word “scale”. The next prompt will be for entry of a new password. If desired, enter a new password. To disable password protection, press the Space Bar once, then press Enter.

The keyboard provided on the 4693 controller is read by the #476 card located at the bottom inside of the controller door. In the bottom left corner of the 476 card are two (2) red LED’s. One is dedicated to the processor chip on this card, and blinks on/off like a heartbeat to show proper operation of the processor. The other LED provides a visual indication that a key press on the keyboard is properly read. Press the suspect key(s) while watching this LED. If the LED does not blink each time the key is pressed, the key has most likely failed. If the LED does blink, but the controller does not properly respond, the 476 card may be defective. Contact Thompson Scale for further assistance and to purchase replacement parts required.

The 4693 controller is provided with a switching power supply input for source 110 VAC power. This power supply does an excellent job of filtering “noise” and voltage/frequency variations in the source 110 power. However, it cannot filter out everything. It is possible that your source 110 VAC supply to the controller is subject to surges, spikes, sags, etc. that are more prominent than normal. Check the source power, and possibly install a line conditioner to see if this eliminates the problem. Call Thompson Scale for a recommendation on line conditioners.

EMI/RFI from Inductive loads. A device such as a solenoid valve coil or relay coil, or transformer style pilot light, are all considered as inductive devices. When the coil of this device is energized via one of the checkweigher’s outputs, a magnetic field is created around this coil. When the device is de-energized, this field collapses, causing a momentary current inrush to occur. This inrush current can feed back to the output that originally turned on the device, and in extreme cases, can cause the controller to reset. Install a snubber (quench arc) across the COIL of the device. This should eliminate the problem. Contact Thompson Scale for recommendations on snubbers and their proper installation.

Static discharge is another possible source of this problem. Make sure that a proper ground has been attached to the weigh station conveyor (make sure it’s loose enough not to interfere with weighing) and controller. Static build-up on the conveyor belt is kept to a minimum by use of our standard anti-static belting.

The reject output is operated by one of two outputs within the checkweigher controller. First, it is important to determine the reject configuration for your application. It is possible to have an input from a metal detector, providing timed reject output, and a reject for low weight, high weight, and metal contaminated product. The configuration for these rejects can be found in the configuration menu. Please reference your user’s manual for instructions on how to find and configure this variable.

Timers are provided in the checkweigher controller; Main Menu item #4 “Set Time, Date, Reject Time”. A setting for a reject delay (time it takes for the rejected package to reach the reject device), and reject duration (time required to actuate the device). If the reject duration is set to 0.0, the reject output will NOT come on.

Checkweighers with reject devices operated by other controls (system motor controls, etc) most likely require only a pulse reject output to the external controls, with the external controls providing the timing functions. In these cases, the reject delay should be set to 0.0, and the reject duration to approximately 0.3 second

If the reject device is operated via the checkweigher controller directly, and packages are not reliably discharged from the reject, it is possible that the #473 I/O card in the controller is experiencing problems. Replace this card to confirm. The reject device itself may also be experiencing problems, with too low air pressure, a sticking or erratically operating solenoid valve, or an air cylinder that has a bad seal or sticky shaft. Check and confirm proper operation of each of these components.

If the Early Weight Terminate photo-eye at the discharge end of the weigh station conveyor has become blocked for more than 15 seconds, an alarm is triggered, turning on these three outputs. This can be caused by mis-aligned or dirty photo-eyes, or a production line stoppage that has placed a container in front of this photo-eye.

The LCD display module is composed of several components, including a conductive rubberized strip that lies between the LCD circuit board and the LCD glass. If corrosion or product contamination gets into this area, it can cause a loss of continuity between the strip and glass, presenting a blank (off state) line on the display. Due to the precise orientation of the strip to glass, it is not practical to disassemble and clean this area since proper re-assembly is extremely difficult.

The LCD should be replaced, and care should be taken to ensure product dusts or gasses do not enter the enclosure.

The 4693 checkweigher or filler controller includes a hard display reset that invoked every 15 seconds. This reset re-writes the display screen from top to bottom, and the flicker or flash seen is the very fast moving re-write line as it moves down the screen.

The LCD graphics module uses a fluorescent back light provided with an adjustment for contrast. Over time, the back light may loose some efficiency and require adjustment. Open the controller door and locate the #476 card at the bottom of the door. In the upper left corner of the 476 card is a daughter card with a connection of two white wires to the display’s back light. Just to the right of this daughter card is a small blue potentiometer with a white center. This is the contrast adjustment. Adjust as necessary. If this does not resolve the problem, contact Thompson Scale for further assistance.

Too heavy product crossing the scale, causing the conveyor motor to overload and stall. Can also be caused by products being too close together, with more than one package on a conveyor at one time.

Failure of the conveyor motor. Although unlikely, the motor can become damaged by excessive loads or missue. Replace motor and return to factory for testing.

Belt tension too tight, causing high friction with slider bed and bearings. Belt tension should be only tight enough to reliably transport packages across the conveyor. Loosen the belt, apply the heaviest package to the center of the conveyor, and then turn the conveyor on. The conveyor should start and the package move across the conveyor without any belt slippage.

Product build-up between belt, bearings, and bed. Clean conveyor and return to service.

Interlock to up/down stream conveyors may intermittently start and stop the checkweigher as part of overall line traffic control.

Conveyor under too much load, stalling conveyor. The Sonic 350 conveyors use servo motors that are instructed to run to a certain “infinite” count. When the motor stalls and then is again able to run, the motor programming requires that the servo catch up to the supposed current count value. This causes the motor to race for a second or so until it has caught up, then returns to the proper operating speed.

Loss of communication with the controller’s #477 card. This card sends instructions to each motor, in return receiving an acknowledgment from the motor. Replace this card and test again.

Blown motor fuse. Each motor is protected by an individual 3AG 1 Amp glass fuse, found on the motor control panel next to the switching power supply. Check fuses.

Motor speed set to zero (0), or motor parameter settings changed. Motor speed can be set in the configuration menu. Along with this speed setting are settings for acceleration, deceleration, and other important motor parameters. Check user’s manual for further information on these settings.

Not enough test weight on scale.
The heavy-duty checkweigher is typically provided with a 500 Lbs. load cell. The average weigh station conveyor weighs approximately 250 Lbs., using up ½ of the load cell’s capacity (this is called dead-load). A test weight of at least 5% (25 Lbs.) should be used to calibrate the scale. A weight less than this will not create enough of a difference (span) between no test weight and the applied test weight for the controller to recognize as a valid weight. Keep in mind that the controller’s calibrated operating range is 2 times the size of the test weight. If the unit is calibrated with 25 Lbs., the controller can only weigh up to a 50 Lbs. product weight, and then will display an “Over Scale” error.

Too much test weight on scale.
The standard heavy-duty checkweigher has a full-load capacity of approximately 150 Lbs. If the weigh station were calibrated with 100 Lbs. of test weight, the low-end weights (partially filled or bags broken open) weighing less than 5 Lbs. may not be detected by the checkweigher. Calibration test weight size is typically 50 Lbs., which yields a maximum weighment size of 110 Lbs., and can easily detect weights down to about 2 Lbs.

Load cell damage in scale base.
It is possible for a load cell to receive two types of damage; mechanical overload and shock overload. Mechanical overload, such as applying 200 Lbs. to a 100 Lbs. scale, simply distorts the elements within the load cell to a point where they do not return to their previous state, and calibration cannot be done reliably or at all. Shock overload, such as dropping a 50 Lbs. bag onto the same scale. The 50 Lbs. bag itself is not enough to overload the scale, but the acceleration force of the dropped bag is. Calibration with a damaged load cell will present drift, erratic weights, and non-repeatable calibration checks. Load cell replacement is recommended.

Flexure damage within scale base.
The scale base, below the weigh station conveyor, consists of two parallel sets of flexure plates suspending the “live” portion of the scale from the “fixed” portion of the scale, and a load cell. The flexure plates are precisely positioned to provide very linear and repeatable weights over the range of the weigh station conveyor. If a flexure plate becomes bent or knocked out of alignment, the scale will loose its ability to function properly. Usually a visual inspection by a scale technician can find this type of problem. Replacement flexure plates are available from Thompson Scale’s stock.

– Not enough test weight on scale. The heavy-duty checkweigher is typically provided with a 500 Lbs. load cell. The average weigh station conveyor weighs approximately 250 Lbs., using up ½ of the load cell’s capacity (this is called dead-load). A test weight of at least 5% (25 Lbs.) should be used to calibrate the scale. A weight less than this will not create enough of a difference (span) between no test weight and the applied test weight for the controller to recognize as a valid weight. Keep in mind that the controller’s calibrated operating range is 2 times the size of the test weight. If the unit is calibrated with 25 Lbs., the controller can only weigh up to a 50 Lbs. product weight, and then will display an “Over Scale” error.

– Confirm power supply is working properly. All DC voltages are generated by the 472, and are used to power the 474 Load Cell Digitizer card. If any LED on the front face plate of the 472 Power Supply Card is not lit, remove power from the controller, then remove the 472 card and replace the failed fuse with one of the on-board spares.

– Check for 10 VDC output to load cell. Using a digital electrical meter set to VDC, and with the scale controller on, place the leads on the 474 Load Cell Digitizer card terminals 1 and 5. The output should be 10 VDC, plus or minus less than 1%. If the voltage is lower or higher than this value, it may indicate a defective Load Cell Digitizer card or Power Supply card.

– Check Load Cell. Using a digital electrical meter set to mV (millivolts), and with the scale controller on, place the leads on the 474 Load Cell Digitizer card terminals 3 and 4. A load cell rated at 2mV/V (total output of 20mV since we excite the load cell with 10 VDC) should have a reading 2 to 12 mV with nothing on the scale (except the weigh station conveyor). The mV reading should increase by about 2 to 4 mV when the test weight is applied.

A load cell rated at 3mV/V (total output of 30mV since we excite the load cell with 10 VDC) should have a reading of 3 to 20 mV with nothing on the scale (except the weigh station conveyor). The mV reading should increase by about 3 to 5 mV when the test weight is applied.

Filter Frequency in the configuration menu has been set to zero (0). Enter the configuration menu, as described in the manual, and confirm this setting. Normally it should be set to 5.

Number of system photo-eyes set incorrectly. Enter the configuration menu, select item #8 (Get Next Menu), then select “P) Photo-Eye Configuration”. This setting should be equal to the actual number of photo-eyes connected to inputs within the controller. If there are no photo-eyes associated with your checkweigher, this value should be zero (0). If there are no photo-eyes, but this value is set to 1 or 2, the checkweigher program is awaiting an input from the photo-eye to trigger termination of the weighment, and will never display a weight value.

Weigh station installation is critical to proper and repeatable weights. The product entering and leaving the weigh station should be as smooth as possible. In-feed and discharge conveyors surrounding the weigh station should be at the same level and speed. Gap between conveyors should be kept to a minimum, since too large a gap will allow the product to “nose dive” into the head roller of the weigh station.

Support structure for the weigh station must be isolated and stable. A structure tied to in-feed or out-feed/reject conveyors will induce low-frequency vibrations into the weigh station scale, affecting weight accuracies.

Conveyor belt tension is very important. Running the belt too tight will cause excessive loading on the weigh station rollers and excessive friction of the belt against the slider bed. The belt should be loose enough to lift at the center between the head and tail rolls, and you should be able to slide your hand between the belt and slider bed, touching the V-guide on the underside of the belt. Another way to adjust this tension is to place your heaviest package on the weigh station conveyor and then start the conveyor. The belt needs to be only tight enough to start without slippage of the belt.

In a perfect world, the weigh station conveyor and scale would be totally isolated from all surrounding structures and electrical connections. Unfortunately this isn’t possible, and electrical connections for the weigh station conveyor motor and any accessory photo-eyes or other devices must be made. These connections MUST have enough slack (we usually recommend a 6″ service loop) between the connection point on the conveyor and the fixed structure near the conveyor. A motor connection made with flexible conduit (Seal-tite) or S.O. cord that is tightly tied down will restrict the movement of the conveyor, and will adversely affect weight.

The weigh station bearings must be properly maintained to provide accurate and repeatable weights. If the bearings are worn or have partially failed, the drag and mechanical “noise” generated by the bearing will affect weights. Between the head and tail rolls on the weigh station, and located on the underside of the conveyor, is an idler roll. This roll holds the belt up and away from the weigh station scale lid. If the bearings fail in this roll, it will cause drag and mechanical “noise”. Check the roll to make sure it spins freely.

The head and tail rolls on the weigh station are precision balanced prior to installation. This balance allows the rolls to turn at any speed without generating low-frequency vibrations (kind of like an out-of-balance tire on your car). If the shaft of the roller becomes bent, due to mechanical impact or over-tightened belt, the roller will generate low-frequency “noise” and affect the accuracy of the scale.

The weigh station conveyor length and speed have been specifically configured for your application. These two factors, along with your product length, provide Thompson Scale with enough information to formulate the highest possible production rates at the right speed, and provide enough weighment time for each package. If however the conveyor speed is changed or a new longer package is introduced into production, sufficient weighment time may not be possible. Contact Thompson Scale with information on maximum product length, conveyor length, and conveyor speed. We will quickly calculate minimum weighment times, and make recommendations on possible solutions to your application problem.

Along with the minimum weigh time, described above, it is also very important that only one product is on the scale at one time. For systems without an exit-end photo-eye (called our Early Weight Terminate photo-eye option), the leading edge of the package must be about 1/4 of its length off the weigh station before we terminate the weighment cycle on that package (20″ long package would have to be 5″ onto the down-stream conveyor) If the weighment cycle of the first package is not completed prior to entry of another package, weight from the second package will influence the final weight of the first. Make sure that packages are properly spaced.

Scale damage will also affect weight. The scale provided below the weigh station conveyor should provide reliable, accurate, and linear weights across the weigh station conveyor. Place the controller into the Calibration Check mode, and then place a test weight at the center of the weigh station. Record the displayed weight, then move the test weight to each corner of the weigh station. The values in each corner should be +/- 2 increments of the center weight value. If one or more corners are out of tolerance, then the scale base may require service. Contact Thompson Scale to discuss your readings and possible solutions.

The checkweigher controller monitors the load cell output as its only source of weight data. If excessive vibration causes high weight readings to occur while the checkweigher is trying to take a weighment, over-weight values will be generated. It is possible to enter a TARE or container value in the product setup for each product you run. Make sure that the TARE on the static scale is the same as that of the product setup.

Inaccurate calibration or loss of valid calibration. The checkweigher controller uses values defined in calibration to determine product weights crossing the scale. If this calibration was performed improperly, such as using a 2 kg. weight but entering a 5 Lbs. test weight value in the controller, the package weights would not be calculated properly. If a significant change occurs to the scale’s load cell, such as overload damage, hitting the weigh station conveyor with a forklift, removing the weigh station conveyor and then replacing, interference from motor or photo-eye connections, it will affect calibration.

Operating Zero can be affected by removing built-up product on the weigh station conveyor and scale. The operating zero is maintained by an automatic zero tracking program within the checkweigher’s program. However, this feature can only zero out a maximum of ½% of the load cell capacity at one time. If more than ½% is added or removed at one time, it will be necessary to enter into the Calibration Check screen and manually zero the scale. If this is not done, it may take several package weights to fully re-zero the scale.

Differences in the static scale and the checkweigher’s scale. It is quite possible that the static scale and checkweigher just differ in what is displayed on a package weight. This difference is almost always a small amount, such as 1 or 2 increments different. The static scale may not have the same accuracy or resolution as the checkweigher. If this is the case, it is dangerous to try and compare an accurate scale with one having less accuracy. The static scale should have at least the same accuracy and display resolution as the checkweigher, and best case, should be about 2 times as accurate as the checkweigher.

Weighment cycle too short. A package must be on the checkweigher for a minimum period of time to generate an accurate and repeatable weight. Run the package across the scale 10 times, writing down each weight. Are the weights the same, +/-0.5%? If not, most likely there is not enough time for the checkweigher to properly weigh the package. Contact Thompson Scale for further assistance.

It is possible to enter a TARE or container value in the product setup for each product you run. Make sure that the TARE on the static scale is the same as that of the product setup.

Inaccurate calibration or loss of valid calibration. The checkweigher controller uses values defined in calibration to determine product weights crossing the scale. If this calibration was performed improperly, such as using a 2 kg. weight but entering a 5 lb. test weight value in the controller, the package weights will not be calculated properly. If a significant change occurs to the scale’s load cell, such as overload damage, impacting the scale conveyor, removing the conveyor and then replacing incorrectly, interference from motor or photo-eye connections, it will affect calibration.

Operating Zero can be affected by removing built-up product on the scale conveyor and scale. The operating zero is maintained by an automatic zero tracking program within the checkweigher’s program. However, this feature can only zero out a maximum of ½% of the load cell capacity at one time. If more than ½% is added or removed at one time, it will be necessary to enter into the Calibration Check screen and manually zero the scale. If this is not done, it may take several package weights to fully re-zero the scale.

Differences in the static scale and the checkweigher’s scale. It is quite possible that the static scale and checkweigher just differ in what is displayed on a package weight. This difference is almost always a small amount, such as 1 or 2 increments different. The static scale may not have the same accuracy or resolution as the checkweigher. If this is the case, it is dangerous to try and compare an accurate scale with one having less accuracy. The static scale should have at least the same accuracy and display resolution as the checkweigher, and best case, should be about 2 times as accurate and the checkweigher.

This LED is provided as a “heartbeat” indicator. As long as the LED blinks on and off at a steady pace, the controller’s CPU is operating properly. If this LED is continuously ON or OFF, consult the factory for more in-depth trouble shooting assistance.

If an updated program EPROM was installed into your controller, it is possible that a feature has been moved or modified as part of the updated program. Contact us for more information on your specific program.

Password is required, but either don’t know it or don’t have one. Press front panel ESC key until display shows Main Menu. Select item 5 (Select/Edit Product), then 3 (Edit Password). When asked for password, type in the word “scale”. The next prompt will be for entry of a new password. If desired, enter a new password. To disable password protection, press the Space Bar once, then press Enter.

The keyboard provided on the 4693 controller is read by the #476 card located at the bottom inside of the controller door. In the bottom left corner of the 476 card are two (2) red LED’s. One is dedicated to the processor chip on this card, and blinks on/off like a heartbeat to show proper operation of the processor. The other LED provides a visual indication that a key press on the keyboard is properly read. Press the suspect key(s) while watching this LED. If the LED does not blink each time the key is pressed, the key has most likely failed. If the LED does blink, but the controller does not properly respond, the 476 card may be defective. Contact Thompson Scale for further assistance and to purchase replacement parts required.

The 4693 controller is provided with a switching power supply input for source 110 VAC power. This power supply does an excellent job of filtering “noise” and voltage/frequency variations in the source 110 power. However, it cannot filter out everything. It is possible that your source 110 VAC supply to the controller is subject to surges, spikes, and sags that are more prominent than normal. Check the source power, and possibly install a line conditioner to see if this eliminates the problem. Call Thompson Scale for a recommendation on line conditioners.

EMI/RFI from Inductive loads. A device such as a solenoid valve coil or relay coil, or transformer style pilot light, are all considered as inductive devices. When the coil of this device is energized via one of the checkweigher’s outputs, a magnetic field is created around this coil. When the device is de-energized, this field collapses, causing a momentary current inrush to occur. This inrush current can feed back to the output that originally turned on the device, and in extreme cases, can cause the controller to reset. Install a snubber (quench arc) across the COIL of the device. This should eliminate the problem. Contact Thompson Scale for recommendations on snubbers and their proper installation.

Static discharge is another possible source of this problem. Make sure that a proper ground has been attached to the weigh station conveyor (make sure it’s loose enough not to interfere with weighing) and controller. Static build-up on the conveyor belt is kept to a minimum by use of our standard anti-static belting.

The reject output is operated by one of two outputs within the checkweigher controller. First, it is important to determine the reject configuration for your application. It is possible to have an input from a metal detector, providing timed reject output, and a reject for low weight, high weight, and metal contaminated product. The configuration for these rejects can be found in the configuration menu. Please reference your user’s manual for instructions on how to find and configure this variable.

Timers are provided in the checkweigher controller; Main Menu item #4 “Set Time, Date, Reject Time”. A setting for a reject delay (time it takes for the rejected package to reach the reject device), and reject duration (time required to actuate the device). If the reject duration is set to 0.0, the reject output will NOT come on.

Checkweighers with reject devices operated by other controls like system motor controls most likely require only a pulse reject output to the external controls, with the external controls providing the timing functions. In these cases, the reject delay should be set to 0.0, and the reject duration to approximately 0.3 second

If the reject device is operated via the checkweigher controller directly, and packages are not reliably discharged from the reject, it is possible that the #473 I/O card in the controller is experiencing problems. Replace this card to confirm. The reject device itself may also be experiencing problems, with too low air pressure, a sticking or erratically operating solenoid valve, or an air cylinder that has a bad seal or sticky shaft. Check and confirm proper operation of each of these components.

If the Early Weight Terminate photo-eye at the discharge end of the weigh station conveyor has become blocked for more than 15 seconds, an alarm is triggered, turning on these three outputs. This can be caused by misaligned or dirty photo-eyes, or a production line stoppage that has placed a container in front of this photo-eye.

The LCD display module is composed of several components, including a conductive rubberized strip that lies between the LCD circuit board and the LCD glass. If corrosion or product contamination gets into this area, it can cause a loss of continuity between the strip and glass, presenting a blank (off state) line on the display. Due to the precise orientation of the strip to glass, it is not practical to disassemble and clean this area since proper re-assembly is extremely difficult.

The LCD should be replaced, and care should be taken to ensure product dusts or gasses do not enter the enclosure.

The 4693 checkweigher or filler controller includes a hard display reset that invokes every 15 seconds. This reset re-writes the display screen from top to bottom, and the flicker or flash seen is the very fast moving re-write line as it moves down the screen.

The LCD graphics module uses a fluorescent back light provided with an adjustment for contrast. Over time, the back light may loose some efficiency and require adjustment. Open the controller door and locate the #476 card at the bottom of the door. In the upper left corner of the 476 card is a daughter card with a connection of two white wires to the display’s back light. Just to the right of this daughter card is a small blue potentiometer with a white center. This is the contrast adjustment. Adjust as necessary. If this does not resolve the problem, contact Thompson Scale for further assistance.