The electronic universal testing machine shows this situation in 1999 when it is turned on. It may be that the CPU operating frequency (11.0592MHz) is abnormal, and the crystal oscillator should be replaced on the same day. If the voltage of the input terminals of the two sensors is too high (usually a few millivolts), check whether the sensors are normal? The common data obtained by using a multimeter to measure the resistance of the sensor is: the input end is about 405Ω; the output end is about 340Ω; the resistance of the two leads at either end and the other end is 280Ω. Note: The data at the input and output of the sensor sometimes varies with the manufacturer, but the change is in a certain proportion. If the comparison voltage of the two operational amplifiers is abnormal, can the resistance of the 2 and 3 pins of the measuring amplifier be changed? If the resistance occurs, it should be replaced. If the above conditions are normal, the operational amplifier of the electronic universal testing machine is damaged and should be replaced. If the indication value drifts or jumps randomly, if the 220V voltage of the power supply is unstable, a regulated power supply should be configured.
If the amplifier output voltage is unstable, replace the amplifier. Check whether the CPU frequency (11.0592MHz) and the analog voltage are stable or drift? If there is a virtual soldering problem, it should be re-soldered; if the performance of the components deteriorates, it should be replaced to check whether the circuit board is damp or oily, stop necessary cleaning and do a good job of dry disposal. If the power transformer has input and no output, replace the transformer or rewind the transformer; if the voltage regulator circuit of the electronic universal testing machine is abnormal, check the corresponding bridge diodes, filter capacitors and the corresponding connection lines, and replace the damaged ones. Welded or open circuit should be re-soldered. Check whether the digital circuit voltage is +5V.
