Author Topic: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)  (Read 7474 times)

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Offline maxwell3e10

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #25 on: June 03, 2023, 05:05:49 pm »
It is an impressive stability, only 1-2 uV. But the statistics is still wrong, maybe the smoothing filter messes it up. It also would be interesting to download the data and plot, see how many digits are used internally.
« Last Edit: June 03, 2023, 05:08:28 pm by maxwell3e10 »
 

Offline iMo

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #26 on: June 03, 2023, 05:21:52 pm »
It does smoothing with "moving average" - how many samples do you average?

PS: What is the architecture of the ADC in that nice meter? We can see the AD7175 ADC there, as well as parts used in the Mutlislope (even though no fpga or mcu in the inguard?)..
« Last Edit: June 03, 2023, 05:38:43 pm by iMo »
 

Offline Kleinstein

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #27 on: June 03, 2023, 06:18:00 pm »
They say that they use a sigma delta ADC and chances are this would be the AD7175 and not an extra seprate build one. The AD7175 is a slightly off choice, more made for high speed, but still OK. The relatively fast ADC may be used to get still relatively fast trigger / start of a measurement. A slower SD ADC may have too much delay at the start.
Noise wise the AD7175 should be good enough, even with a background check of the ADC and ref. divder gain.

Chances are there is a µC for the ingurad part, as there is a 2nd crystal or clock generator besides the one at the ADC. Chances are the 16 pin chip next to it and close to the signal isolators would be something like a µC.
 
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Offline iMo

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #28 on: June 03, 2023, 07:17:42 pm »
Unbelievably complex inguard board, however.. My first thought had been it is a kind of multislope with 7175 as the rundown something..  :D
 

Offline Kleinstein

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #29 on: June 03, 2023, 07:33:16 pm »
The circuit indeed looks quite complicated for just a simple single channel DC voltmeter.
As an extra function there is the contact checking mode via capacitance, but I would not expect that much circuit for this either.

There some relatively large ceramic capacitors connected to the four ADG1211 switches. This looks a lot like switching capacitors for voltage division.
So this gives quite a few chips to replace some recision resistors.

It gets a little more complicated from having some kind of ACAL - though still no reason for that much circuit (e.g. 1 x ADG1208, 1-2 relays and some resistors should be enough).
 

Offline HighVoltageTopic starter

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #30 on: June 04, 2023, 10:11:40 am »
Here the measurements have been running over night with the same settings.
The smoothing filter is set to Average over 10 measurements

 
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Offline iMo

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #31 on: June 04, 2023, 12:10:24 pm »
FYI noise with RAND() and 1uV resolution.
« Last Edit: June 04, 2023, 12:15:47 pm by iMo »
 

Offline DavidKo

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #32 on: June 05, 2023, 06:00:56 am »
While Keysight 34470A and keithley DMM7510 had a dramatic price increased in the last few years, this Hioki Voltmeter has been stable.

Since the warranty has expired on my DM7276-01, and if there is any interest, I could open it up and take some pictures from the inside.

I like Hioki products, but for home user their products are not too much interesting. When the products are out of the support, they do not calibrate the device nor send the calibration/service manual (same experience with Japan and Czech support). Compared to mentioned Keysight or Keithley, where the calibration adjustment procedure is available.
 

Offline HighVoltageTopic starter

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #33 on: June 05, 2023, 07:07:11 am »
While Keysight 34470A and keithley DMM7510 had a dramatic price increased in the last few years, this Hioki Voltmeter has been stable.

Since the warranty has expired on my DM7276-01, and if there is any interest, I could open it up and take some pictures from the inside.

I like Hioki products, but for home user their products are not too much interesting. When the products are out of the support, they do not calibrate the device nor send the calibration/service manual (same experience with Japan and Czech support). Compared to mentioned Keysight or Keithley, where the calibration adjustment procedure is available.

That is very true.
Japanese companies in general do not like to give out service manuals or calibration procedures or schematics.
However their products are usually very good.

Keithley and Keysight are going more and more in the same direction and I would not be surprised, if they also would not supply calibration procedures in the future.
 
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Offline ap

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #34 on: June 05, 2023, 01:23:02 pm »
Unless its broken, and given the fact that this Hioki is DCV only, one can get away with verification. This way the drift history is not covered either by re-adjustment.
Metrology and test gear and other stuff: www.ab-precision.com
 

Offline aronake

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #35 on: January 21, 2024, 05:16:55 pm »
The voltage reference board read BT4560 in the corner, indicating that it is the same voltage reference board as in BATTERY IMPEDANCE METER BT4560:

https://www.hioki.com/in-en/products/resistance-meters/battery/id_5897

There are sellers on Taobao who claim to have ADR1000 for sale.

https://item.taobao.com/item.htm?abbucket=5&id=761537983785&ns=1&spm=a21n57.1.0.0.5256523cWu7jic

They are on very similar voltage reference boards with an ADR1000 but read DM7275. So it looks like ADR1000 may be used in newer models, and as has been indicated that Linear is now selling it for companies using it in products.
 
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Offline gamalot

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #36 on: January 21, 2024, 07:20:08 pm »
They chose OPA2140 on their LTZ1000 board.

Offline gamalot

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #37 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.  :-//

Offline Lajt

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #38 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
 
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Offline laichh

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #39 on: February 22, 2024, 03:14:28 am »
Sorry to go off topic again, are these resistor values 1.58K? I have never seen such top marking before.  :-//

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

Offline gamalot

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #40 on: February 22, 2024, 11:40:24 am »
Sorry to go off topic again, are these resistor values 1.58K? I have never seen such top marking before.  :-//

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

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.

Offline gamalot

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Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)
« Reply #41 on: February 22, 2024, 11:42:11 am »
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

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


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