I just connected my brand new Joulescope to my precise power supply outputting 6v and confirming it with 7,1/2 digit precision multimeter (6.0005v). My average reading from joulescope is 5.828v which is way out of spec.
I tried recalibrating it but it didn’t help. Any ideas where the issue is coming from?
Hi @kapouchima and welcome to the Joulescope forum! Thanks for purchasing a Joulescope, and great to hear that you are working to validate your instrument!
First, please restore your JS220 offset calibration to the factory calibration:
Then, please see section 9.2 of the Joulescope JS220 User’s Guide for how to make a voltage-only measurement:
The Joulescope JS220 is an extremely high-impendance instrument. Unfortunately, this means that we have intentionally omitted the pull resistors (typically 1 MΩ or 10 MΩ) found in most oscilloscopes and multimeters. When unconnected, the V+ and V- inputs will float due to the very small input bias currents for the front-end opamps. You also have to create a connection to keep both V- and V+ within ± 15V of I+. The easiest way is to short V+ and I+.
Does this fix the issue for you?
Thanks for the help, after I post the issue I found similar description from the forum and it fixed the problem.
My initial understanding was that voltage probes and current probes are totally isolated.
Great to hear that this solved the issue!
All JS220 terminals are electrically isolated from USB ground. However, all JS220 terminals are referenced to I+ and must remain within ±15V from I+.
