Hi all,
Received my DMM6500 today, first impressions were good so I started to set up an experiment whereby I would use the 10MΩ input impedance as a shunt resistor in DCV mode to measure the leakage of a capacitor when 10V applied to the other side of the capacitor.
To my surprise, both the 100mV and 1V manual range setting gave me "Overload" even though the reading in the 10V range is 0V (1PLC).
Going back to basics, I disconnected everything and the overload disappeared. Then I attached the input leads with nothing connected on the ends; Overload.
Switching from Measure to Digitizer, at the slowest rate 1KSPS, I can clearly see lots of 50Hz mains on the graph.
(I'm assuming both ADCs use the same input amplifier circuitry)
In my lab, it ranges from 1Vpp-3Vpp. (various combinations of switching equipment off & lights off & using grounding wriststrap)
In my outdoor workshop, it ranges from 100mVpp-200mVpp. (lights off, then on)
So that explains the why; the input amplifiers are saturating and triggering hardware overload detection.
A couple of acquaintances of mine fired up their 34401A's, attached floating leads and placed them in worse case positions (near SMPS and power strips) and the 34401A works fine on the minimum range.
Is my DMM6500 faulty, or does it have poor isolation by design? Perhaps I need to shield everything or scale back my expectations?