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Classification and Maintenance of Digital Weighbridge Instrument
Function and setting of digital weighbridge instrument
1、 Functions of instruments; Measure the change (voltage or current) of the sensor on the scale platform; 2、 Classification of instruments; 1. A/D conversion weighing instrument: all such instruments adopt high resolution; 2. Digital weighing instrument: this type of instrument is used with digital sensor,; Section V Operation, maintenance and common troubleshooting; 1、 Allowable axle load; The maximum load of the oversized vehicle shall not exceed the maximum weight of the scale; Note: axle load is the total load of the rear axle (including axle group) of the vehicle; The allowed weighbridge axis and sensor capacity, and the fulcrum of the weighbridge sensor;
1、 Function of instrument
Measure the weight of the weight on the platform by measuring the change of the sensor (voltage or current), and give instructions in digital form.
2、 Classification of instruments
1. A/D conversion weighing instrument: this type of instrument adopts high-resolution high-speed A/D digital to analog converter, and provides a full range of instruments with different functions according to different user needs. Users can select the most suitable product according to their own needs.
2. Digital weighing instrument: this type of instrument is used together with digital sensor, with built-in calibration program. It can be debugged for each sensor, which is simpler, more efficient and more accurate than the traditional debugging method.
Section V Operation, Maintenance and Common Troubleshooting
1、 Allowable axle load
The maximum load of the over weighed vehicle shall not exceed the maximum weight of the scale.
Note: The axle load is the total load of the rear axle (including axle group) of the vehicle.
The axle of the weighbridge is related to the sensor capacity, the distance between the fulcrum of the weighbridge sensor and other factors. Generally, the weighbridge is not allowed to approach short wheelbase vehicles such as forklifts.
The instrument shall be preheated before startup, generally about 15 minutes; When off duty, the power must be cut off, and the sensor plug cannot be plugged or unplugged when the power is on. If the setting parameters, time and date of the instrument need to be changed, please refer to the user manual of each instrument for detailed operation and requirements. If the system is configured with computer, printer, large screen display and other external devices, the operation, online connection and maintenance of these external devices are shown in their respective product manuals.
When driving on the scale platform, the vehicle speed is required to be less than 5 km/h, then brake slowly, measure after the vehicle stops stably. Note: the vehicle should travel in a straight line and stop at the center of the scale platform as far as possible.
3、 Daily inspection and maintenance
During the use of the weighbridge, the daily inspection and maintenance should be strengthened mainly in the following aspects: (1) whether the weighbridge body is stuck; (2) Check whether the limit stops; (3) Whether the sensor inclines; (4) Whether the wiring of the junction box is loose; (5) Whether the connection of instrument, computer, display and keyboard is firm; (6) Misoperation causes loss of tare or gross weight. Specifically, it includes the following aspects:
Check and adjust the levelness of the table top. Due to various reasons, the platform of the weighbridge body is more or less deformed after being used for a long time. The longer the time is used, the more severe the deformation is, resulting in inconsistent force on the sensor. To change this situation, only the adjustment of the potentiometer is not enough (if the error is within the range of 20~30kg, the potentiometer can be used to adjust). The height of the sensor should be adjusted first. It should be noted that when one sensor is adjusted, other sensors will also change. Repeat the adjustment for several sensors. ◆ Precautions for instrument use: (1) The instrument can only use a separate lighting power supply, and it is strictly prohibited to lead from the three-phase four wire, and there is no other equipment that produces interference in the same power supply; (2) The instrument power supply shall be provided with a separate ground wire; (3) There is no interfering equipment near the weighing platform.
The key to whether the bearing platform is qualified is: the diagonal dimension of the four sensor stress points (the diagonal error is within 4mm), and the left and right deviations (within ± 1.5mm) and front and rear deviations (within ± 2mm) based on the centerline;
Check whether the wiring is correct, whether there is looseness, broken wire, short circuit, etc. If found, repair it immediately;
There shall be no stones, coal and other foreign matters stuck in the clearance around the platform;
Regularly check whether the limit clearance is reasonable, and the limit bolt shall not collide with the scale body. Generally, the clearance is 2~3mm;
The connector shall be maintained every half a year, and the support head shall be coated with grease;
Clean the platform frequently and keep it clean, and repaint the surface paint regularly (once a year is recommended);
It is prohibited to conduct arc welding on the scale platform. If it is necessary to conduct arc welding on the scale platform, the following points should be noted: disconnect the signal wire from the instrument; The ground wire of arc welding must be set near the welded part and firmly contact the scale body; Do not make the sensor part of the arc welding circuit.
4、 Instrument maintenance
Check whether the wiring is loose and broken, and whether the grounding wire is firm;
Keep the junction box dry, and replace the desiccant in the box regularly. Once moist air and water drops enter the junction box, use a hair dryer to dry it.
Operators and maintenance personnel shall be specially trained before operation and maintenance.
Replace the instrument PCB board: for the frequently used weighbridge, once the instrument is damaged, it is difficult to find the fault at the moment. In order not to affect the use, the instrument PCB main board can be replaced (it is recommended that the user purchase a PCB board for standby at the same time when purchasing the weighbridge). Steps for replacing PCB board:
(1) Cut off the instrument power supply;
(2) Open the instrument, disconnect all connectors on the PCB motherboard, and record the location of the connectors;
(3) Remove the screws that fix the PCB motherboard and remove the motherboard;
(4) Install the standby motherboard and connect the plug-in;
First of all, we need to find the fault of truck scale. The easiest way is to use the simulator to find it. Steps: connect the signal line between the junction box and the instrument
Release, connect the simulator to the instrument and connect the power. If the instrument works normally, it indicates that the fault is on the scale platform. If the instrument works abnormally, it indicates that the fault is on the instrument. If the fault is at the instrument and the customer cannot repair it by himself, he must inform the company's special maintenance personnel to repair it; If the customer needs to use the scale in an emergency, the user can replace the PCB board and use it. The damaged PCB board should be sent to a special person for repair.
Analysis of scale platform failure: first check the junction box to see if there is moisture intrusion. If there is moisture, scrub it with alcohol, then dry it with an electric hair dryer, and clean the interior. Next, find out whether there is a short circuit in the wiring. Use a multimeter in the junction box to measure the resistance between the shielded wire and other wires and the scale platform for leakage and short circuit; At the same time, check whether there is leakage and short circuit between each wire and ground wire or stainless steel shield wire on the outer layer of signal wire. If short circuit is found, replace the wire. If no problem is found in the above search, it can be preliminarily determined that the sensor is faulty. The steps to find the sensor fault are as follows: use a multimeter to check the resistance value between positive excitation (+EX) and negative excitation (- EX) in the junction box (measured on the signal wire terminal leading to the instrument in the junction box), and the resistance value is about 400 Ω/N (N is the number of sensors); Or use a multimeter to measure the resistance between the positive output (+Si) and the negative output (- Si) of the total output terminal, which is about 2500 Ω/K (K is the number of sections, and there are two sensors in one section). If the resistance value is incorrect, the sensor is faulty. Use this method to continue to find other faulty sensors.