Digital display controllerThe external wiring includes power supply, input signal, and output signal. Therefore, when abnormal display phenomena are found, the first step is to use a multimeter to test the rear terminal signal, which should be within the required value of the instrument. For example, when the instrument does not display when powered on, the first thing to check is whether the instrument power supply is abnormal. If it is normal but the instrument still does not display, it can be concluded that the internal power supply or related components of the instrument are damaged; When there is overflow or jumping on the display, the input signal can be measured to see if there is an open circuit or poor contact. If an open circuit is detected, the fault occurs outside the meter. After identifying the signal open circuit, it can be resolved and normal operation can be achieved; When the measured temperature is lower than the given value and the circuit ammeter is still zero, a multimeter can be used to measure the output signal of the rear terminal of the instrument. Normally, it should be 10mA. If not, it indicates that there is a problem with the instrument itself. If there is, but the circuit current still does not indicate, it can be concluded that the fault occurred outside the instrument, that is, there is a problem with the matching ZK-1 thyristor voltage regulator or ammeter, which can be further searched and judged. By checking the signal on the rear terminal of the instrument, it can be determined whether the fault is inside or outside the instrument.