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2. Failure Analysis and Maintenance Method This failure is rare because the low-frequency pulses of this model or this series of devices can be received by the error calculator under normal conditions. We used an oscilloscope to perform pulse waveform display and observe the changes in waveform amplitude. As a result, it was found that the amplitude of the measured waveform was not significant (about 1V), and the trigger pulse amplitude of the general error calculator was between 2 and 4.5V. , obviously can not receive this pulse signal normally.
The key component that determines the pulse amplitude of the device under test is the optocoupler. This device uses a 4N25 model (some devices use the TIL113) optocoupler integrated circuit. If its sensitivity is not good or the magnification is not enough, this failure will happen.
3, troubleshooting First open the cover of the device, and then open the cover of the standard table, find two optocoupler integrated circuit 4N25 film in the pulse output section, replace it with the same type of film, and then use an oscilloscope to test The amplitude of the waveform is significantly increased, and finally connected to the error calculator, the pulse shows that everything is normal.
4. Similar fault analysis and processing (1) Fault phenomenon Using a CL311 three-phase multi-function standard meter as a standard to measure a ST-9020 single-phase power meter verification device, a similar fault phenomenon occurs and the standard meter receives no pulse. However, using the PS42A error calculator as an error display is working properly.
(2) Test and analysis In order to clarify the cause of the fault, the oscilloscope is used to measure the low-frequency pulse output of the device under test, and its pulse amplitude is 2.5V. Then connect the low-frequency pulse output end of the device under test to the pulse input of the standard meter. The measured pulse amplitude is reduced from 2.5V to about 1V, which greatly attenuates the amplitude of the waveform. Before and after the test data shows that due to the poor load capacity of the optocoupler of the device under test, the CL311 standard table cannot be sampled normally.
(3) Processing method In order to increase the amplitude of the low-frequency pulse output from the school device, a +5V power supply and a 5kΩ resistor R in the CL311 three-phase standard meter low-frequency pulse input circuit are connected in series and connected to the positive input of the low-frequency pulse. End, as shown in the figure (this figure only changes the first channel, other channels need to be changed and so on. To adjust the input low-frequency pulse amplitude can be achieved by changing the 5kΩ resistance value, the resistance value is The value range is generally between 2.5kΩ and 5kΩ). Then the voltage and current of the device under test is increased to the rated value (220V, 5A). Then the amplitude of the low-frequency pulse is measured with an oscilloscope. Its amplitude is increased to about 2V. Observe the measurement error display of the CL311 three-phase standard meter. . 
In addition, it should also be noted that the changed line has no effect on the low-frequency pulses input by other standard instruments and meters. As a result, the CL311 three-phase multi-function standard meter expands the measurement range on the basis of the original use, and particularly provides convenience for on-site testing.
Analysis and Treatment of Special Faults in Check Meter of Electric Energy Meter
1. Failure phenomenon A model BY2082C1 single-phase portable power meter calibration device has a low frequency pulse output at the pulse output end of the calibration, but this pulse cannot trigger the PS42A error calculator, resulting in no error display of the error calculator. The instrument cannot be made to calculate errors.