Electronics > Metrology

Hioki DM7276-01 Precision DC Voltmeter (9 PPM)

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gamalot:

--- Quote from: laichh on February 22, 2024, 03:14:28 am ---
--- Quote from: gamalot on January 22, 2024, 04:05:04 am ---Sorry to go off topic again, are these resistor values 1.58K? I have never seen such top marking before.  :-//

--- End quote ---

1.58 kohm is correct, these resistors are likely made by KOA.

--- End quote ---

I have a lot of small light blue KOA Speer chip resistors and most of them don't have top markings, even the 0603 size ones.

gamalot:

--- Quote from: Lajt on February 21, 2024, 10:56:37 pm ---If anyone is interested, I've made a DIY temperature probe for Hioki DM7275, DM7276 & RM3544.
The build is documented on https://lajtronix.eu/2024/02/21/diy-hioki-dm7275-76-temp-probe-z2001/
It has been tested and is working great.

Br, Lajt

--- End quote ---

I happen to have a Z2001 sensor that came with my RM3545, maybe I can do some simple measurements on it.

Alex Nikitin:
Well, I've purchased the DM7275-03 for my home lab. So far I am quite happy with what this small unit does. I like that it is completely quiet, seems to be very stable and as arrived did differ about -3ppm from my usual standards (which I count as about 10ppm accuracy in any case). The input current measures about -20pA and seems to be stable and not noisy. The temperature measurement feature is very handy and useful. I am already getting some good data on the low frequency noise of my HP3245A and other sources, with the passive filter the baseline noise is about 600nV p-p in 0.1-10Hz range at 1NPLC.

I have a question though - does anybody knows a calibration company in the UK which would calibrate this unit with traceability, data and uncertainties (to my surprise, the unit came without any calibration data from the manufacturer).

My next home project now could be to build a universal shunt box for the Hioki and the HP3456A, to measure DC currents from about 100uA FS to 1A FS. I have good 10K and 1R0 references but it would be much more convenient to have a box with proper range switching and fuses.

Cheers

Alex

alm:

--- Quote from: Alex Nikitin on April 19, 2024, 11:49:46 pm ---I have a question though - does anybody knows a calibration company in the UK which would calibrate this unit with traceability, data and uncertainties (to my surprise, the unit came without any calibration data from the manufacturer).

--- End quote ---
I have no suggestion for a lab, but you'll need a lab with sufficiently low uncertainties (check their scope of calibration) that doesn't mind doing something they may not have a procedure for. The calibration procedure in the manual (see attachment) should be straight-forward for any cal lab with the right equipment. So I don't see why it would be difficult for them to produce a traceable certificate with data and uncertainties. Adjustment may be more tricky, but do you really need adjustment? Can you not live with just knowing the offsets?

I'm a bit surprised there is no linearity check like a negative voltage or say 50% of range in the calibration procedure. I didn't study the design, but is the linearity guaranteed by design?

Alex Nikitin:
I did some checks on zero volt, range and polarity change, and in general errors are not more than 1LSB (which for the range change could be 1ppm of value, measuring +/-1V at 10V range). The zero drift on 100mV range with a shorted input is below 50nV for 10min, the offset noise on Slow speed is ~350nV p-p (and that is without offset correction). Which means this small thing might be as good a Null-Meter as the HP3458A (and might be even better as it stays cool unlike most accurate bench meters).

On calibration I am not worried too much especially as the difference between the meter at 10V and my own references is slowly getting smaller in time and now below 2ppm. However it might be nice to have a way of adjusting the unit in the future, and that should increase the value, as HIOKI policy on second hand units is simple - they would deal only with the original owner, as far as I understand.

Cheers

Alex

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