Frequently Asked Questions - Heavy Duty Checkweigher FAQs
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.
