Home › Forums › Mooshimeter Support › Miscalibrated?
- This topic has 15 replies, 2 voices, and was last updated 8 years, 3 months ago by admin.
When I hold the leads together (connected to Ω and C), it shows something around 0Ω, but swings around all over the place. It’s usually around .6Ω but I’ve seen it go as high as 1200Ω. Am I doing something wrong?
That does sound very odd… So with no leads attached at all and in resistance mode, what resistance does the meter show? Around 1200 ohms? It should read OVERLOAD with no leads attached.
With a 14ga jumper mine reads 1.7 ohms. This is not crazy as most meters are somewhat similar and you just remember that as your zero point.
But them I though of the zero button!
However, it changes the reading to -7.90 ohms. Very disconcerting at first. I am sure you will get this working in due time. It will be great if we could use this as a relative mode and be able to baseline to zero any reading. However, I beleive there should be some visible warning that it is in relative mode and the “actual size may be larger than it appears”
Doh. I know what that 7.9 ohms is. It’s not a miscalibration. The meter measures the ttotal resistance it sees, which includes the resistance of the protection elements. The protection elements’ resistance is subtracted back out as the final step before displaying a reading. So when you zero the meter in resistance mode it will subtract the protection element resistance from zero, resulting in -7.9 ohms. The order of operations should be changed, fixing now. Thanks
FYI – fixed in Android app:
Working on iOS
Here’s a video:
It does show overload if the leads aren’t touching.
On Friday, I ran some calibration tests on the meter with our Fluke Calibrator. I tested VAC, VDC, IAC, IDC, Resistance.
My meter looked good with a less than 0.5% error on each reading type, so I don’t think there are any calibration issues.
I can post some of the results if you want.
That is a very strange behavior, haven’t seen that before. I’ll send you a shipping label on Monday so you can return the unit for diagnosis and will get you a new one. Sorry for the trouble!
Can you share more about the test you did? Independent validation is really helpful.
Here are my results: https://www.dropbox.com/s/yorsd4pj30ifxq9/Mooshim%20test%201-30-2015.xlsx?dl=0
For your reference, it was tested on a Fluke 5080a
Mine doesn’t seem to handle resistance metering correctly, either before or after the firmware update. With no leads connected, and the top channel set to Showing Aux Voltage DC/Ohms above and A/1.2V/V below, the resistance displayed slowly changes over time (in a stable environment). As an exmaple, while I typed this comment I watched it drift from -0.65 to -0.72 and it’s still changing in that same direction. The second channel is set to Votage DC/V and A/60V/V and sitting right at 0.0000 or -0.0001 and stable. Checking known resistance resistors and a few handy potentiometers side by side show my other 2 meters match, but the mooshimeter doesn’t seem to have any idea what to do with resistance :)
If I plug in leads and check DC voltage between V/C and a slightly old 9V battery, it reads accurately against another meter, and same for checking AC voltage. Given the resistance readings seem to be acting odd, I haven’t done any current measurements.
I think this is a problem of unclear UI – sorry!
The Ω input can measure several different values. When you first select the channel it is measuring “Aux Voltage DC”. That’s the voltage at the Ω terminal. It is drifting because it’s a floating input with nothing connected.
If you tap the button saying “Aux Voltage DC” it will change to “Aux Voltage AC”. Tap it again and it will say “Resistance”. Then you can measure resistance at the Ω terminal.
Here’s a crash course for the app as well.
Have 1.3 (48) and I know you acknowledged this issue above, but I have found a new wrinkle…
When Resistance is on the top screen….
“Zero” does nothing.
When Resistance is on the bottom screen…
“Zero” sets to -7.89.
(IMHO I am getting very confused as to which readings can be put on top and which on bottom. If I had my druthers, I would vote for radio buttons or a simulated selector switch like on a Fluke. But that is me thinkin crazy)
That issue is fixed just a few builds down the road from the one you have now.
Apple has an approval process even for beta releases. Grumble grumble. Fixed zeroing behavior will be available soon.
Sorry….my enthusiasm to help assumed that all this was happening in real time.
If all bugs and improvements are in github, maybe I should just “hang out” there?
For some reason, tapping the aux voltage dc button does nothing on my iPhone with the app version on there (which is why I was confused that it’d never register any resistance). When I used the testflight version on my iPad, it works fine (but I didn’t have the stock app on the iPad, so I can’t say that the button would or wouldn’t have worked there w/ the app-store version). My iPhone is my ‘production’ iOS device so I don’t want to testflight it, but I’ll uninstall the testflight version on the iPad, reinstall the stock app from the app store, test the channel tap button, and if it works, I’ll uninstall the app store version on the iPhone and try re-installing it. Thanks!
That’s quite strange… there’s nothing exotic about those buttons. Thanks and let me know how it goes. Obviously the apps are evolving pretty rapidly – the feedback has been really helpful.