[Nut-upsuser] Fwd: Cyberpower usbhid-ups wrong battery voltage
davoremard at gmail.com
Mon Apr 14 22:10:57 UTC 2008
Although there is quantization of reported values,
it should be calibrated to match the measured number to the
true physical value. That's my opinion, however. I think
calibration makes a traceable match between the reported
value and physical value.
Cyberpower however hasn't confirmed yet that this is applicable
for both old and new 0x0501 devices (no reply about this yet)
Best regards, Davor
On 4/11/08, Arjen de Korte <nut+users at de-korte.org> wrote:
> > IMHO everything that measures something should be subjected
> > to periodic calibration being it a 5-digit precision laboratory voltmeter
> > or cheap piece of junk like ups, both can benefit from being
> > calibrated with higher precision instrument (not only to improve
> > measured values but also to determine the errors and repeatability
> > of the measurement)
> Your UPS reports a zero based 8-bit value for the battery voltage, which
> is about 210 bins at a real value of 13.6V. This gives it a resolution of
> almost 65mV. No calibration in the world can improve that. Even when
> assuming zero non-linearity error and -tolerance, this is already way too
> coarse to use this to base any action upon when it comes to 12V lead-acid
> batteries. If users have a clue to decide if a reported battery voltage of
> 13.5V would be good or bad in the first place anyway.
> My point is, it would be measuring without meaning.
> > Hopefully the model detection will make it and at least the coarse
> > conversion factor would be there for cyberpowers and others that
> > need it.
> I'll be happy to include this if CyberPower can confirm that this
> adjustment is applicable to all 0x0501 productid's, both past *and*
> present models.
> Best regards, Arjen
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