- This topic has 7 replies, 2 voices, and was last updated 7 years, 1 month ago by
.
- Posts
The restance reading of the meter is off by 3.6 ohms. When I short the probes together I get 3.6 ohms. If I measure a 5 ohm resistor I get 8.6ohms. I’ve tried the zero function, but no luck. What else can I try?
I stuck the meter in the freezer and noticed that when the internal temp dropped the resistance decreased as well. So at around 14 degrees, when the probes were shorted together the resistance dropped to 2.8 ohms.
Greg, I brought up the same thing back in November[1]. There is a protection device that adds a few ohms. It should be possible to zero that out, but the zero function didn’t work for me, either.
[1] https://moosh.im/f/topic/low-range-resistance-measurements/
Hi Greg and John,
This is correct, there’s a protection device inline that adds a few ohms. The device is a PTC fuse rated to 600V, so if you miswire the meter it won’t be damaged. PTC stands for positive temperature coefficient, which is why you saw the resistance drop when you put it in the freezer.
Hope this helps, best
~JamesThanks for the info John and James.
Could the firmware or the app compensate for the PTC at least for room temperature – or using the internal thermocouple and a simple table for a wider range of ambient temps? Would be really nice to read zero for a good short – or as close to zero as possible.
Cheers.
Hi Paul,
The firmware and app already try to compensate for the value of the PTC, the problem is that the value of the PTC changes with time, temperature and overload events. This is why the Mooshimeter’s specs say “resistance between 20Ω and 20MΩ”. After zeroing out the resistance readings should be accurate in the very low range, but I’m reading reports that the zeroing feature isn’t working for some users, so I’ll try to address that soon.
Best
~JamesUps
Posted in wrong thread :Low-range resistance measurements
In my case it is working only “50%” in the Mooshimeter beta.
The upper part saves the the value, in my meter ~9,67 ohm but only keeps subtracting it until it shows the first time overload. Than it is still printed in the ZERO field but no longer subtracted.
In the lower part it works as expected.
Hope it helps fixing the problem …
