| Electronics > Repair |
| Please help, FLUKE 8920A Multimeter Repair |
| << < (44/45) > >> |
| daisizhou:
Do you mean to preheat the 8920a host for more than 15 minutes,Connect a 50 ohm load to the 8920A mainframe input port. Then follow the instructions on page 4-19 "DC Offset resistor selection",Select AC, press the "RANGE HOLD" button, and switch to the 2v position,Switch the digital multimeter to the mv position, connect the red probe to TP3, and the black probe to the metal housing (GND),Observe the reading of the digital multimeter. If the reading is greater than 1mv, adjust R72 to make the reading less than 1mv.The actual measurement is (-0.59mv - -0.67mv) Then keep the above operation,Press the "AC+DC" button,Observe the digital multimeter reading,If the reading is greater than 1mv, adjust R26 to make the digital multimeter reading less than 1mv.The actual measurement is (1.39mv-1.46mv) Finally, I would like to ask, will this adjustment affect the overall accuracy of the 8920A host? |
| Harry_22:
You are simply try to set zero volts on the low range so that the device stops jumping on the high range. |
| daisizhou:
--- Quote from: Harry_22 on June 20, 2024, 11:41:36 am ---You are simply try to set zero volts on the low range so that the device stops jumping on the high range. --- End quote --- Sorry, I still don't quite understand. For adjusting R72, the TP3 voltage is (-0.59mv - -0.67mv), and the manual requires it to be less than 1mv. For adjusting R26, the TP3 voltage is (1.39mv-1.46mv), and the manual still requires it to be less than 1mv Also, when the picture shows "1.348", it means that the standby time is more than 15 minutes, and the pointer swing will automatically disappear. At this time, press "LO RANGE ENABLE" and the screen will display 1.348. I don't know which adjustment is the most correct one. In order to test the accuracy, I conducted the following test |
| daisizhou:
After recording data for a long time, I found that TP3 voltage is related to key selection. Follow steps 1 to 8 in paragraph 4-48 on page 4-19 of the Service Manual.Adjust R72, TP3 voltage is (-0.59mv--0.67mv). Adjust R26, TP3 voltage is (1.39mv-1.46mv) After the 8920a host is preheated for more than 15 minutes, the analog pointer will no longer swing back and forth.TP3 voltage is always (-0.59mv--0.67mv) or (1.39mv-1.46mv) I'm a little lost, I don't know how to adjust them,Is the most correct choice |
| Harry_22:
Try to set up zero voltage for both cases. Don't be afraid it won't get any worse. |
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