Hi,
I have a Fluke 189 meter with a problem and I am in need of help with troubleshooting it: when set in DCV mode, with no probes connected, the meter will display a reading between 75 and 80 mV.
And, interestingly enough, if I measure the voltage between the COM and V input jacks with another (high input impedance) multimeter, I actually measure 75-80 mV.
If I do the same using a standard 10/11 MOhm input impedance meter, I measure roughly half of that (i.e. 35-40 mV or so) - and both the measuring meter and the Fluke 189 will display this new value.
Next, if I switch the Fluke 189 to DCmV mode (again, no probes connected), the readings start rising as if charging a capacitor (I don't remember if they eventually settle to any specific value).
Back to DCV mode, I measured the input impedance of the Fluke 189, but the readings kind of confuse me (the 189 meter was set to manual range mode, and I measured resistance between COM and V terminals for the different ranges as below):
Range (V) | | 5 | | 50 | | 500 | | 1000 |
Measurement_1 (MOhm) | | 11.60 | | 10.65 | | 10.55 | | 10.54 |
Measurement_2 (MOhm) | | 9.57 | | 8.85 | | 8.78 | | 8.77 |
[Edit] And, of course, I forgot to mention what Measurement_1 and Measurement_2 represent.
Measurement_1 is resistance read when connecting the positive lead of the measuring meter to the V input jack of the Fluke 189, and, correspondingly, with the negative lead connected to the COM input jack of the Fluke 189.
Measurement_2 is resistance read when swapping the leads (i.e. positive lead going to COM of the Fluke 189 and negative lead going to V).
[/Edit]
I also checked the main components in the input protection section - PTC, fusible resistor, MOV's - and the (in circuit) measurements are similar to those on a Fluke 89 IV board which I know is good.
Does anyone have any suggestions where to look and what to check next, please?
Thanks!