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Spikes for a range of 100 V and NPLC = 1 and NPLC = 0,1

DMM7510 7½-Digit Graphical Sampling Multimeter
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Ilya Grudovik
Posts: 19
Joined: October 30th, 2018, 1:54 pm
Country: Belarus

Spikes for a range of 100 V and NPLC = 1 and NPLC = 0,1

Post by Ilya Grudovik » November 15th, 2018, 6:43 am

Discovered curious spikes for a range of 100 V and NPLC = 1 and NPLC = 0,1. Other NPLCs look pretty ordinary.

The file with the data is attached.

Emissions are not large and fit into the instrument specification. But they look like some kind of problem :( May be software.

FW 1.6.4
Attachments
100V_1NPLC_DMM-1 Run 17 2018-11-12T02.23.13.png
100V_1NPLC_DMM-1 Run 17 2018-11-12T02.23.13.png (202.78 KiB) Viewed 1874 times
100V_0,1NPLC_DMM-1 Run 18 2018-11-12T02.30.25.txt
(453.6 KiB) Downloaded 122 times
100V_0,1NPLC_DMM-1 Run 18 2018-11-12T02.30.25.png
100V_0,1NPLC_DMM-1 Run 18 2018-11-12T02.30.25.png (124.43 KiB) Viewed 1874 times

Ilya Grudovik
Posts: 19
Joined: October 30th, 2018, 1:54 pm
Country: Belarus

Re: Spikes for a range of 100 V and NPLC = 1 and NPLC = 0,1

Post by Ilya Grudovik » November 15th, 2018, 6:58 am

Data:
Attachments
100V_1NPLC_DMM-1 Run 17 2018-11-12T02.23.13.txt
(461.7 KiB) Downloaded 123 times

Andrea C
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Re: Spikes for a range of 100 V and NPLC = 1 and NPLC = 0,1

Post by Andrea C » November 20th, 2018, 1:54 pm

The 5 ppm offset error term for the 100V range would allow for as much as 500uV.
Like you indicated, it well within the stated accuracy for the instrument.

On my DMM7510, I see similar spikes at about every 1.68 seconds. Turning the auto zero off makes them go away.
So seems there is some temporary artifact that remains after the auto zero relays are used to look at internal references.
But, it is very much within the performance spec for that range.

Ilya Grudovik
Posts: 19
Joined: October 30th, 2018, 1:54 pm
Country: Belarus

Re: Spikes for a range of 100 V and NPLC = 1 and NPLC = 0,1

Post by Ilya Grudovik » November 20th, 2018, 2:07 pm

In Firmware v1.6.7c emissions on the 100V range are gone !!!

But they appeared on the ranges of 0.1V - 10V with the input connectors open and the input resistance 10MΩ.

Emissions go exactly 160 measurements. I would venture to suggest that the problem is in synchronization with the frequency 50Hz. When the measurement does not get to the right place.

450µV in range 0,1V = 0,4%. I understand that output 10 Mom works as an antenna. But even compared to the noise level, these emissions are huge. And they are suspiciously regular. Every 160 measurement is erroneous. This is not a signal. This is a false indication :(

See attachment:
Attachments
DMM-1 Run 12 2018-11-21T00.32.33.txt
(44.63 KiB) Downloaded 109 times
DMM-1 Run 12 2018-11-21T00.32.33.png
DMM-1 Run 12 2018-11-21T00.32.33.png (298.14 KiB) Viewed 1760 times

Andrea C
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Re: Spikes for a range of 100 V and NPLC = 1 and NPLC = 0,1

Post by Andrea C » November 20th, 2018, 2:30 pm

In the measure settings, what is the state of Line Sync?
It is off by default. Try turning it on, if these spikes are problematic to your use case for the instrument.

Also, open circuit condition is not, in my opinion, good method when trying to access the voltage offsets. For current measure offsets, yes absolutely. For voltage offsets, I like a low thermal EMF short circuit applied to front terminals.

Ilya Grudovik
Posts: 19
Joined: October 30th, 2018, 1:54 pm
Country: Belarus

Re: Spikes for a range of 100 V and NPLC = 1 and NPLC = 0,1

Post by Ilya Grudovik » November 21st, 2018, 12:42 pm

Andrea C wrote:
November 20th, 2018, 2:30 pm
In the measure settings, what is the state of Line Sync?
It is off by default. Try turning it on, if these spikes are problematic to your use case for the instrument.
Yes, the inclusion of this option solves the problem when NFC = 1. This is in my opinion a way to hide the problem.

Although the precise frequency of these emissions (1 in 160 measurements) is suspicious.
Also, open circuit condition is not, in my opinion, good method when trying to access the voltage offsets. For current measure offsets, yes absolutely. For voltage offsets, I like a low thermal EMF short circuit applied to front terminals.
Oh yeah! Without a doubt. But I was taught that to find a problem in the device, you need to make the problem as visible and easy to repeat as possible.

For example, these emissions also disappear if you disable AutoZero. And this is when Line Sink is turned off.

I believe that these emissions are suspicious dezhe if they do not go beyond the specification of the device. And it seems to me that by paying attention to them and removing their cause can make the device even better. Make it a benchmark in this class of devices.

And you can simply dismiss this problem by referring to the specification.

And this is a matter of firm policy. Does it make the device the best. Or does how to turn out if only fit into the specification. This is not for me to decide. My job is to pay attention.

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