BHR series weighing sensors and other household appliances, as long as the familiar structure principle and circuit it can be serviced, electronic weighing instrument generally with micro controller or processor, the electronic weighing sensor has a program, if the microcontroller or processor is broken, change can only find manufacturers will write the code chip the circuit, every kind of Shanghai Huadong electronic instrument factory instrument, each circuit has its own specialized applications, as long as the microprocessor (mainly software) to solve the problem, other problems are easy to solve.
In the repair process, to use the visual components, exclusion, confirm the repair methods such as combination of use to complete the repair work. As long as the confirmation of which part of the circuit failure, damage, you can proceed to the next step to solve the problem. After these steps can basically find out where the problem lies.
Shanghai automation instrumentation Limited by Share Ltd introduces the common fault of electronic weighing sensors and solutions:
(1) failure to restore after weighing
Check whether the output signal of the sensor value analysis on standard (A/D amplification / use code code / the lowest interest rate range), if the signal is not in standard, adjust the sensor adjustable resistance, the signal value to standard, such as compensation cannot check whether there is a problem in sensor, ensure the sensor output (normal stable scale body) case, lock instrument fault, general amplifying circuit and A/D conversion circuit problems according to circuit principle analysis to determine the test one by one, the ultimate solution to the problem.
(2) fault analysis of inaccurate weighing
Observation of code value is stable, the position sensor is the friction phenomenon, power supply is stable, operational amplifier circuit is normal, using weights weighing whether the average four scale test. Further analysis of the instrument or weight correction according to the instruction.
(3) failure to boot
First determine the non fuse, power switch, power cord and voltage switch caused by the problem, check the transformer AC voltage input and AC output. If the instrument is equipped with a battery, remove the battery and turn on the AC power supply to see if the battery voltage is low. The second detection rectifier circuit, voltage regulator circuit and display drive circuit is abnormal, if there are no problems check processor and accessory circuit is burnt out.
(4) showed garbled
The original display circuit removed, for a normal display circuit to see whether normal. If the display of the normal display circuit problems, if not normal, should check whether the driver circuit is faulty, and finally check the processor shows that the output pin is in a reasonable range of output.
(5) the key is not easy to use
The first key replacement test, new key function is normal, it can be considered as key is bad, line between the measurement key and CPU, no circuit. Check whether there is bad contact with the key support. Measure the key and the CPU circuit on the diode, resistors, such as whether there is a short circuit, open circuit.
(6) can not be called full load
And can not go back to the same situation, most likely due to the small signal input range has changed. According to the method can not be returned to zero, if you can not find a problem, the first detection of power supply, A/D circuit is normal, and then detect the sensor output.
(7) sensor fault identification method
The static measurement method: use the multimeter ohm files, respectively measuring sensor E+ of S+, S- (or E- or of S+, S-) resistance is the same, general error compensation in 0.5 would need to be done, such as excessive error (2 or above) is recommended to replace the sensor.
The dynamic measurement method: the right to host the sensor wiring board, the use of digital meter (four more than half of the better) of the DCV files, the measurement of S+ and S- on the voltage is equal to (0 error), if not equal to sensor compensation.
(8) sensor compensation
The output signal of the sensor is too high. Please add a resistor between the sensor "E+S-" to make the signal to the normal range.
Sensor output signal is too low or -ERR plus a resistor in the sensor "E+~S+" between the value of the signal to the normal range (the lower the resistance value, the higher the sensor output signal).
Method for detecting amplifying code of A/D circuit
The electronic scale debugging to the internal set state (to display the current status code) applied with weighing weight, record the amplified code value, the relationship between them: the original value + full weighing code + security code amplification.
(9) fault analysis of digital instrument
Digital instrument maintenance is relatively simple, only needs to detect the power supply circuit, communication circuit, CPU micro processing circuit and storage circuit and display circuit can, according to instructions of tips, judgment to solve different error phenomenon and actual measurement results. The premise is to ensure the normal performance of digital sensors.