1. Fault Phenomenon A BY2082C1 model single-phase portable energy meter calibration device, during calibration, although outputting low-frequency pulses, failed to trigger the PS42A error calculator, resulting in no pulse display and thus preventing the instrument from calculating errors. 2. Fault Analysis and Repair Method This fault is rare because, under normal circumstances, the low-frequency pulses from this model or series of devices should be received by the error calculator. Using an oscilloscope to display the pulse waveform and observe its amplitude changes, we found that the measured waveform amplitude was small (around 1V), while the trigger pulse amplitude of a typical error calculator is between 2 and 4.5V, clearly indicating that it could not properly receive this pulse signal. The key component determining the pulse amplitude of the device under test is the optocoupler. This device uses a 4N25 optocoupler integrated circuit (some devices use TIL113). If its sensitivity is poor or its amplification factor is insufficient, this fault will occur. [b]3. Troubleshooting[/b] First, open the top cover of this device, then open the cover of the standard meter, find two optocoupler integrated circuit 4N25 chips in the pulse output section, replace them with chips of the same model, and then test with an oscilloscope. The amplitude of the waveform is significantly increased. Finally, connect the error calculator, and the pulse display is normal. [b]4 Similar Fault Analysis and Handling[/b] (1) Fault Phenomenon Using a CL311 three-phase multi-function standard meter as a standard, test an ST-9020 single-phase energy meter calibration device. The result is a similar fault phenomenon. The standard meter cannot receive pulses, but the PS42A error calculator works normally as an error display. (2) Test and Analysis In order to find out the cause of the fault, first use an oscilloscope to measure the low-frequency pulse output of the device under test. Its pulse amplitude is 2.5V. Then connect the low-frequency pulse output terminal of the device under test to the pulse input terminal of the standard meter. The measured pulse amplitude drops from 2.5V to about 1V, which greatly attenuates the amplitude of the waveform. The test data before and after showed that the CL311 standard meter could not sample normally because the optocoupler of the device under test had poor load capacity. (3) Treatment method In order to increase the amplitude of the low frequency pulse output by the device under test, a +5V power supply and a 5kΩ resistor R in the low frequency pulse input circuit of the CL311 three-phase standard meter were connected in series to the positive terminal of the low frequency pulse input, as shown in the figure (only the first channel is modified in this figure, and other channels can be modified in the same way. If the amplitude of the input low frequency pulse needs to be adjusted, it can be achieved by changing the value of the 5kΩ resistor. The value of the resistor is generally between 2.5kΩ and 5kΩ). Then the voltage and current of the device under test were raised to the rated value (220V, 5A), and the amplitude of the low frequency pulse was measured with an oscilloscope. The amplitude increased to about 2V. The measurement error display of the CL311 three-phase standard meter was observed and it was found to be working normally. [img=416,375]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/ybjs/2001-1/52-1.jpg[/img] Furthermore, it should be noted that the modified circuitry has no effect on low-frequency pulses input to other standard instruments and meters. This expands the measurement range of the CL311 three-phase multifunction standard meter, significantly facilitating on-site testing.