[Nut-upsuser] Tripplite SMX1000LCD input Voltage reporting

Yogesh Bhanu yogesh.bhanu at gmail.com
Tue Mar 30 09:05:49 BST 2021


An Update. Thanks to David from Tripplite, he did perform some tests and
was able to reproduce the problem.
Please note the UPS works, just that the reporting is off and is always
Kind Regards,


On Sat, Feb 27, 2021 at 11:09 AM Yogesh Bhanu <yogesh.bhanu at gmail.com>

> Dear Gene et.al,
> Thanks for the insightful reply. I have already involved our Grid
> Electricity Supplier and Solar Company. There is a general consensus that
> the grid company needs to do something. Seems to be general problem here.
> I discovered the issue by chance as the issue autoresolves and the
> inverter monitoring only displays open unresolved faults in its default
> mode.
> My issue is three of four voltage measurements devices I have did measure
> closer to the inverter shutdown voltage and since I was only tracking UPS
> input voltage I did not see the issue with
> high grid voltage hence the reason for my question.
> Have a great weekend.
> Kind Regards,
> On Fri, Feb 26, 2021 at 7:02 AM Gene Heskett <gheskett at shentel.net> wrote:
>> On Thursday 25 February 2021 22:50:05 Yogesh Bhanu via Nut-upsuser wrote:
>> > Hello all,
>> >
>> > I have a Grid Overvoltage issue in my Area 'cause of solar inverter.
>> > Unfortunately the Tripplite ups underreports the input voltage -- It
>> > happens with the Display Panel and with SNMP. I 'm aware that with
>> > SNMP I'm polling the system. So I can never  measure instant input
>> > Voltage. I'm polling at 3s interval without an issue.
>> >
>> > I have tested this with a Wattmeter and a Fluke Digital meter.  The
>> > input voltage is off by alteast 3 - 5 V.  So when the UPS reports
>> > 250.5 V or 251 V the input voltage usually is between 253.5 and 255V
>> > and this is the case when the grid input Voltage is high for 10s at
>> > which point Solar inverter resets.
>> >
>> > My question is,
>> > Is it possible the UPS Display is not reporting Instant input Voltage
>> > ?
>> Its entirely possible since the invertor may take liberties with the
>> waveform delivered, combined with whatever meter you are using's
>> faithfullness to true rms response. With the more squareish waves output
>> by an invertor, the measurement errors can exceed 10%. Bear in mind that
>> most so called rms metering, is only truly accurate at 60 hertz, or 50
>> hertz depending on the environment its meant to be sold into.  The only
>> true way to find out where the error actually lies, is to look at the
>> invertors output with an oscilloscope, but even the eye can be confused
>> if the distortion is seemingly well filtered, in which case a comparison
>> with the sine wave output of a Good audio test oscillator can be
>> informative. See a good explanation for the term rms, which stands for
>> the square Root, of the Mean of the of Sum the squares, which is a fancy
>> way of saying how much heat is generated by a suitable resistor hooked
>> across the src. One massive enough that its temperature is not pulsing
>> from the frequency of the applied voltage which will effect its
>> resistance. This is very difficult to do in a modern digital multimeter
>> because to do it right, they would have to do all that squaring and
>> adding for a complete cycle, or about 6000 times a second, then on the
>> zero crossing, instantly calculate the square root of all that to
>> display it.
>> Doing that, given the power src for such a meter making those claims is a
>> 9 volt battery expected to last 6+ months, is patently impossible.
>> I just bought a new scope, a 4 trace, 350 MHz rated, 2GHz sampler by
>> Siglent, that may be able to do that. It certainly has the horsepower to
>> do it, but I've no clue if the code has been written to do it.
>> Your other choices are a bolometer, generally used for signals above 500
>> MHz, or calorimetric involving measuring the temp rise of the water
>> cooling the resistor, meaning 2 very accurate thermometers, and some
>> means of measuring the water flow, all accurate to .1 degree and .1%
>> flow.
>> If its being a PITB, I believe I'd see if the invertor output could be
>> turned down 1 or 2%. But if the scope says it outputting a square wave,
>> flat across the top and bottom, I'd yell at the invertor maker. Its a
>> BBLB invertor, so expect some additional expense for a smarter one.
>> > Kind Regards,
>> >
>> > Yogesh
>> Good luck Yogesh.
>> Cheers, Gene Heskett
>> --
>> "There are four boxes to be used in defense of liberty:
>>  soap, ballot, jury, and ammo. Please use in that order."
>> -Ed Howdershelt (Author)
>> If we desire respect for the law, we must first make the law respectable.
>>  - Louis D. Brandeis
>> Genes Web page <http://geneslinuxbox.net:6309/gene>
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