Hioki DM7276-01 Precision DC Voltmeter (9 PPM) - Page 1
Forum section: electronics / general

author: HighVoltage
author_rank: Super Contributor
timestamp: June 03, 2021, 12:09:46 pm
content: ThisHIOKI DM7276-01has been added to my lab.It is advertised as a 9ppm/year 7 1/2 digit DC Voltmeter with touch screen a very small footprint and lightweight.Some specs:- 100 mV ( ±120.000 00 mV) to 1000 V ( ±1000.000 0 V ), 5 ranges- High-accuracy model with 1-year 9ppm Accuracy- Capacitance contact check (using built-in C-monitor)- Supports global production with built-in variable power supply- Built-in EXT I/O, LAN, and USB- Outstanding Long-term stability and Temperature characteristics- Excellent noise performance approaching an 8-½ digit DMM- Specifications ideal for everything from R&D to production lines at ¼ the conventional costsI am just starting using this instrument and the first thing that is noticeable is its very fast warmup time from around 3 min, maybe less.Stay tuned, first measurements should be interesting.Anyone here having experience with this instrument?

author: MegaVolt
author_rank: Frequent Contributor
timestamp: June 04, 2021, 07:49:57 am
content: A very interesting find !!How much did it cost?Can you share the documentation that is only available upon registration? "Instruction Manual", "Communication Command Instruction Manual".I am already myself)

author: MegaVolt
author_rank: Frequent Contributor
timestamp: June 04, 2021, 08:17:31 am
content: Teardown?))))))))))))))

author: HighVoltage
author_rank: Super Contributor
timestamp: June 04, 2021, 08:44:19 am
content: In regards to the documentation, here are the direct download linksHIOKI DM7275, DM7276 - datasheet englishHioki product overview - Test equipment for batteries englishHioki DM7275, DM7276 - Manual englishApplication notes:Effect of the measurement target output resistance and voltmeter input resistance on measured valuesMeasurement of the package potential of laminated lithium-ion batteries

author: HighVoltage
author_rank: Super Contributor
timestamp: June 04, 2021, 08:52:39 am
content: Here I tested the warmup time of the DM7276.My LTZ1000 reference was warmed up well, so no influence from that.This little peak shortly before 2 min seems normal for this instrument.It seems within 2 min this DM7276 is warmed up to get reliable values.And this is even faster than the Keithley DMM7510.

author: HighVoltage
author_rank: Super Contributor
timestamp: June 04, 2021, 08:58:53 am
content: In this picture the Hioki DM7276 was hooked up to my LTZ1000A reference over nightSettings:- 100 NPLC- Smoothing filter ON with 5 average readingsThe nominal value of my LTZ1000 reference is 7.065,90xVFor comparison I had the Keithley DMM7510 running in parallel to the Hioki.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: June 04, 2021, 09:05:20 am
content: It is twice as noisy as the 7510...

author: Kleinstein
author_rank: Super Contributor
timestamp: June 04, 2021, 03:44:55 pm
content: Quote from: MegaVolt on June 04, 2021, 09:05:20 amThe factor is visible from the example data, but AFAIK the DMM7510 is very mixed perfomance when it comes to noise. For the data I have see, it is very good in the 100 mV range and also good with short integration like 1 PLC. However with 100 PLC the performance is not that great and a bit disappointing - at least with a lower applied voltage. With the test at 10 V the references could be a main factor.Both meters are not really made for ultimate precision at 100 PLC. The main use is more like relatively fast production tests at 10 PLC or 1 PLC, often with a scanner.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 04, 2021, 06:31:42 pm
content: The Hoki meter is a voltmeter only - so no shunt and not current sources for resistance. This allows for a lower price.Chances are the accurcy specs for the 10 V range are to a large part limited by reference drift. The external temperature regulation for the LTFLU in the DMM7510 has some disadvantage in this respect. The specs are also only estimates about future performance - the actual performance is usually better, but unknown upfront. Some estimates are more conservative than others.

author: guenthert
author_rank: Frequent Contributor
timestamp: June 06, 2021, 05:41:10 pm
content: It's even a DC-only voltmeter, which further simplifies the input stage and eases timing requirements (while the 3458A is often praised here for its precision and linearity, it was really its speed which puts it ahead, more so in '89).I was even wondering why they bother with a multi-range DC-only voltmeter. Why not make it 10V only, simplifying the input stage even further (making it cheaper or more precise) and selling it as digitizer? Seems they are eyeing the currently hot battery market.

author: aronake
author_rank: Frequent Contributor
timestamp: June 01, 2023, 07:13:09 am
content: Do anyone have more experiences to share on this multimeter?Maybe some teardown pictures?Anyone know what voltage reference it uses?Linearity?With the collapse of the Japanese yen is is getting relatively inexpensive from Japan.https://store.shopping.yahoo.co.jp/firstfactory/soku-hioki-dm7276-02.html373K JPY is around 2.7K USD. Some freight etc added of course.

author: aronake
author_rank: Frequent Contributor
timestamp: June 01, 2023, 07:15:07 am
content: Similar price in Europe apparently.https://www.calplus.de/hioki-dm7276-01.html

author: HighVoltage
author_rank: Super Contributor
timestamp: June 01, 2023, 11:24:50 am
content: 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.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: June 01, 2023, 12:07:30 pm
content: Quote from: HighVoltage on June 01, 2023, 11:24:50 amIt is very interesting

author: HighVoltage
author_rank: Super Contributor
timestamp: June 01, 2023, 03:57:44 pm
content: It has an LTZ1000ACH on a separate small board with all SMD components.First set of pictures

author: HighVoltage
author_rank: Super Contributor
timestamp: June 01, 2023, 03:58:36 pm
content: Second set of pictures

author: HighVoltage
author_rank: Super Contributor
timestamp: June 01, 2023, 03:59:53 pm
content: Last set of pictures

author: HighVoltage
author_rank: Super Contributor
timestamp: June 01, 2023, 04:23:38 pm
content: Back together and still working.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: June 01, 2023, 10:23:41 pm
content: Quote from: HighVoltage on June 04, 2021, 08:58:53 amThanks for the tests and teardown. Something seems wrong with Hioki displayed statistics. P-P cannot be less than twice S_n. P_P would be equal to twice S_n if the distribution is purely bimodal, otherwise P_P should be more than twice S_n.

author: laichh
author_rank: Regular Contributor
timestamp: June 02, 2023, 07:55:33 am
content: Here are the inside of a Hioki DM7275, I don't see any different compared against a DM7276, seems identical to me.

author: laichh
author_rank: Regular Contributor
timestamp: June 02, 2023, 07:57:46 am
content: more Hioki DM7275 pictures.

author: HighVoltage
author_rank: Super Contributor
timestamp: June 02, 2023, 09:15:01 am
content: Quote from: maxwell3e10 on June 01, 2023, 10:23:41 pmThis was a quick and dirty setup, definitely not reliable.Let me do a proper hookup and testing.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 02, 2023, 11:48:34 am
content: The inconsistancy between the p-p and standard deviation values has nothing to do with the input signal it is a pure math thing. For a given P-P value one gets the largest RMS value / standard deviation with a kind of square wave and this gets 50% of the p-p value. It is only the SD estimator for a small sample size that adds the extra factor of square root of (N/(N-1)) that can make it slightly larger.The test description indicates more like a longer test.

author: HighVoltage
author_rank: Super Contributor
timestamp: June 03, 2023, 03:31:29 pm
content: Here are the results of 100 measurements with 100 PLC and smoothing filter ONThe source is a stable LTZ1000A

author: HighVoltage
author_rank: Super Contributor
timestamp: June 03, 2023, 04:57:58 pm
content: 1.5 hours later and 1394 measurements laterSame setting

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: June 03, 2023, 05:05:49 pm
content: 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.

author: iMo
author_rank: Super Contributor
timestamp: June 03, 2023, 05:21:52 pm
content: 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?)..

author: Kleinstein
author_rank: Super Contributor
timestamp: June 03, 2023, 06:18:00 pm
content: 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.

author: iMo
author_rank: Super Contributor
timestamp: June 03, 2023, 07:17:42 pm
content: Unbelievably complex inguard board, however.. My first thought had been it is a kind of multislope with 7175 as the rundown something..

author: Kleinstein
author_rank: Super Contributor
timestamp: June 03, 2023, 07:33:16 pm
content: 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).

author: HighVoltage
author_rank: Super Contributor
timestamp: June 04, 2023, 10:11:40 am
content: Here the measurements have been running over night with the same settings.The smoothing filter is set to Average over 10 measurements

author: iMo
author_rank: Super Contributor
timestamp: June 04, 2023, 12:10:24 pm
content: FYI noise with RAND() and 1uV resolution.

author: DavidKo
author_rank: Frequent Contributor
timestamp: June 05, 2023, 06:00:56 am
content: Quote from: HighVoltage on June 01, 2023, 11:24:50 amI 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.

author: HighVoltage
author_rank: Super Contributor
timestamp: June 05, 2023, 07:07:11 am
content: Quote from: DavidKo on June 05, 2023, 06:00:56 amThat 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.

author: ap
author_rank: Frequent Contributor
timestamp: June 05, 2023, 01:23:02 pm
content: 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.

author: aronake
author_rank: Frequent Contributor
timestamp: January 21, 2024, 05:16:55 pm
content: 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_5897There are sellers on Taobao who claim to have ADR1000 for sale.https://item.taobao.com/item.htm?abbucket=5&id=761537983785&ns=1&spm=a21n57.1.0.0.5256523cWu7jicThey 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.

author: gamalot
author_rank: Super Contributor
timestamp: January 21, 2024, 07:20:08 pm
content: They chose OPA2140 on their LTZ1000 board.

author: gamalot
author_rank: Super Contributor
timestamp: January 22, 2024, 04:05:04 am
content: Sorry to go off topic again, are these resistor values 1.58K? I have never seen such top marking before.

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

author: laichh
author_rank: Regular Contributor
timestamp: February 22, 2024, 03:14:28 am
content: Quote from: gamalot on January 22, 2024, 04:05:04 am1.58 kohm is correct, these resistors are likely made by KOA.

author: gamalot
author_rank: Super Contributor
timestamp: February 22, 2024, 11:40:24 am
content: Quote from: laichh on February 22, 2024, 03:14:28 amI 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.

author: gamalot
author_rank: Super Contributor
timestamp: February 22, 2024, 11:42:11 am
content: Quote from: Lajt on February 21, 2024, 10:56:37 pmI happen to have a Z2001 sensor that came with my RM3545, maybe I can do some simple measurements on it.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: April 19, 2024, 11:49:46 pm
content: 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.CheersAlex

author: alm
author_rank: Super Contributor
timestamp: April 21, 2024, 10:35:26 am
content: Quote from: Alex Nikitin on April 19, 2024, 11:49:46 pmI 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?

author: Alex Nikitin
author_rank: Super Contributor
timestamp: April 21, 2024, 11:35:57 am
content: 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.CheersAlex

author: Alex Nikitin
author_rank: Super Contributor
timestamp: April 21, 2024, 03:40:31 pm
content: I am already thinking about building an "extender" for the Hioki, a box with relays and resistors controlled from the I/O connector of Hioki and providing DC current and resistance measurement options. It is not that Hioki can not measure DC current on its own (see the photo below)CheersAlex

author: Kleinstein
author_rank: Super Contributor
timestamp: April 21, 2024, 04:04:00 pm
content: Quote from: alm on April 21, 2024, 10:35:26 amIt is indeed odd that the calibration points are only 0 and full scale. Checking the negative side would be good and not that difficult. It's not a strickt INL test, more a crude check the amplifier / supply is not broken.The ADC is an AD7175 high end SD ADC chip. So the linearity can be pretty good and normally no separate adjustment needed for the positive and negative side. If the design is OK it is unlikely the the meter would develope high INL over time.At the expected linearity level it is anyway a bit tricky to check, as the specs for the usual calibrators are limited (the actual performance may be better).

author: Alex Nikitin
author_rank: Super Contributor
timestamp: April 21, 2024, 10:34:01 pm
content: DM7275/6 has an interesting feature, called scaling, where it is possible to use a linear scaling factor and offset, plus rename the units if required. The scaling coefficients A and B (for A*x +B expression) can be entered from the front panel or remotely with 7 digits precision and later the combination can be saved as a setup and recalled when needed. In essence it makes the unit very convenient to use with current shunts, as long as the shunt is stable enough, the tolerance doesn't matter much as it can be corrected out. The unit also offers a (linear) parametric correction from temperature sensor readings, up to +/-1000 ppm/C. I did make a nice 1 Ohm reference recently using a precision hermetic high-current JRL 1 Ohm resistor, the same resistor asevaluated on xDevs. The resistor I've used measured about + 560 ppm and I just found almost exact correction resistor value. However with the HIOKI one can use one of these JRL resistors as is and just calibrate the error out by scaling when use it as a shunt to measure current.Actually the scaling can be used as a user calibration option to correct for the reference drift if needed one day.CheersAlex

author: Alex Nikitin
author_rank: Super Contributor
timestamp: April 23, 2024, 10:02:10 pm
content: I did some measurements on the capacitive coupling of my bench meters to the mains ground (i.e. to the meter case in all three units)for another thread on the forum here. The newcomer came on top by not a small margin, to my surprise:Hioki DM7275-03Positive input to mains ground - 10V range and below <30pF, 100V and 1000V <10pFNegative input to mains ground <30pFBetween input terminals ~1500pF for 10V range and below*, <10pF for 100V and 1000V ranges.Here I can add that I also measured the DC leakage to ground from measuring terminals with my Keithley 617 electrometer: for +100V above the ground the leakage is 2.5pA, for -100V it is -6pA.CheersAlex* - possibly something to do with the contact checking feature, even if it is OFF. The cure is simple (if the input C is a problem) - to put a 10K resistor in series with the positive lead and use Hi-Z, on 10V and below the meter has ~20pA input current or ~0.2uV added error with the resistor.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: April 24, 2024, 09:52:04 pm
content: Six days continuously powered on, the HIOKI is settlings down nicely, the difference with my reference meters and Fluke 731B is now essentially gone, the initial difference of about -3ppm has disappeared in about 3 days time and the meter appears to be stable - however I will continue to monitor its stability. Here just as an illustration the HIOKI measuring the Fluke 731B for 60 min when the temperature in my home lab was reasonably constant (the TC of 731B is about -2ppm/C, so the 0.2ppm rise over 60 min means the temperature has dropped by about 0.1C ). The red line is 30s running average, vertical scale is 1uV = 0.1ppm /div. It is good to see two low noise references (LTZ1000A and RefAmp) working well together.CheersAlexP.S. - I've corrected the graph's title, the measurements were made at NPLC10, 1s intervals, not NPLC1 .

author: Alex Nikitin
author_rank: Super Contributor
timestamp: May 07, 2024, 09:16:21 pm
content: Here is another measurement result using the DM7275, in this case I was trying to do a 1000:1 transfer of resistance, from Fluke 742A-10K to my 10 Ohm DIY shunt (made using a TO-3 packaged Vishay Foil resistor). The Keithley 263 is used as 1mA current source to supply the Fluke and 10R shunt in series, the voltage on the Fluke was monitored by HP3456A and was stable at 10.00046V (double checked with the Hioki), the Fluke 742A-10K has a measured resistance of 10.00005K so the current was about +41ppm from 1mA. As a control option the ESI SR1010 resistor was used as a 10R shunt in place of my DIY one. Despite some meters of cables and numerous connections, the circuit offset at the shunt was measured below +/- 50nV average, 250nV p-p variations (the Keithley 263 has some useful features to change the current polarity and also switch it on/off so it was easy to measure offsets without disturbing the wires and connectors). The graph below shows two 15min runs with two 10R shunts in this configuration. The temperature variations (measured by Hioki) were below 0.5C). A linear trendline was added to each run to indicate a possible drift in time. Vertical scale is 100nV /div (=10nA/div, or 10ppm of value) , horizontal is samples/time , 1min/div, (=15 samples).CheersAlex

author: HighVoltage
author_rank: Super Contributor
timestamp: May 08, 2024, 09:37:51 am
content: Your 1000:1 transfer results are very impressive with the old Keithley 263 as a 1mA source !Please show a picture of your complete setup.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: May 08, 2024, 01:01:58 pm
content: I had to tidy up the cabling a bitand let it settle for 10 min or so. Also today the lab temperature is somewhat higher and the HP3456A shows 10.00044V on 10K Fluke (and that is the HP tempco shows, the Keithley is stable as Hioki shows 10.000463 on the Fluke).The Keithley 263 is a very stable and capable instrument even at higher currents, my unit is repaired and fully recapped, and for most part I use it over the newly acquired HP3245A, mostly for convenience reasons but it is not that far in DC performance and similar in the LF noise area.CheersAlexP.S. - on the photos, the first one is measuring the offset only (the current source is OFF), the second is +1mA current, the third is -1mA current. The Keithley is very symmetrical in polarity switching, due to its architecture.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: May 08, 2024, 01:11:15 pm
content: Here is a longer run (1mA from K263 into 10R DIY shunt) in the night time, the temperature change was about 1C over that period. The orange line is averaging for 5min (75 samples) . Vertical scale 50nV/div, horizontal - time.CheersAlex

author: Alex Nikitin
author_rank: Super Contributor
timestamp: May 10, 2024, 03:31:11 pm
content: Here in an interesting result with the same 10R DIY shunt and Keithley 263 supplying +/-100nA, so the voltage measured is +/- 1uV, with the HIOKI on FAST (NPLC1) speed (~30s/sec), 10 sec OFF, 10 sec +100nA, 10sec -100nA and last 10 sec OFF. The orange line is 5 samples moving average.CheersAlex

author: Alex Nikitin
author_rank: Super Contributor
timestamp: May 14, 2024, 06:50:04 pm
content: I rather like the temperature measuring feature. Strangely, if you copy data to a USB stick, the temperature measurements are what is on the screen, with 0.1C resolution. However if you request the data remotely, the resolution is 0.01C which does make a lot of difference! Below the results of an overnight run with the Hioki measuring the Fluke 731B 10V output and the room temperature at the same time. I plan to use the DM7275 together with a small DIY "temperature chamber" for tempco measurements on resistors and references.CheersAlex

author: EC8010
author_rank: Frequent Contributor
timestamp: May 22, 2024, 06:46:47 pm
content: Going back to the lovely internal pictures, the difference between the 7276 and 7275 is that the black dot is in the A box on the voltage reference board whereas it's in the C box on the 7275. Looks like they graded the stability of the reference board. Which seems entirely reasonable. Perhaps more significantly, it might mean that the DMM's drift is dominated by the voltage reference rather than input stage and ADC noise/drift? If so, it might be possible to improve a 7275.

author: HighVoltage
author_rank: Super Contributor
timestamp: May 23, 2024, 11:03:06 am
content: Quote from: EC8010 on May 22, 2024, 06:46:47 pmThere is almost a $1000 price difference between the DM7275 (20 ppm) and the DM7276 (9ppm) modelsResolutions are the same.You might be right, same as the differences in the Keysight 3458A models.BTW, I used the Contact Check Function of the 7276 for the first time consciously.

author: chekhov
author_rank: Regular Contributor
timestamp: May 23, 2024, 11:45:19 am
content: Quote from: HighVoltage on May 23, 2024, 11:03:06 amEh, having so much space on display they show "NoCntct" instead of "NoContact", lameAlso, from the first seconds this is a little bit of cheating on low voltage input - "guessed" DMM in 10M input mode.If it was in auto or was a different similar class DMM - it's evident when the input is not connected by readings jumping all around. Of course, for automated measurements that could be much more versatile function.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: May 24, 2024, 09:22:22 am
content: Quote from: HighVoltage on May 23, 2024, 11:03:06 amHow does it work? What would it show if the battery was working?

author: chekhov
author_rank: Regular Contributor
timestamp: May 24, 2024, 10:17:43 am
content: Here is a little description from 158 page of user manual, provided in the beginning of this thread:

author: MegaVolt
author_rank: Frequent Contributor
timestamp: May 24, 2024, 10:43:08 am
content: Quote from: chekhov on May 24, 2024, 10:17:43 amIf we put a thin insulator between the terminal and the battery, will the test pass?

author: wanghar
author_rank: Contributor
timestamp: July 06, 2024, 10:10:09 am
content: How to calibrate a DM7276/7275? Does this descriped anywhere in the manual?

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 06, 2024, 07:25:59 pm
content: Quote from: wanghar on July 06, 2024, 10:10:09 amCalibration is described on page 212 of the user manual, however Adjustment (next page) is password protected and not accessible. It would be good to know the adjustment password!CheersAlex

author: wanghar
author_rank: Contributor
timestamp: July 08, 2024, 10:01:56 am
content: Is this Hioki's style that not allowing users to do calibration by themselves?

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 08, 2024, 05:33:14 pm
content: Quote from: wanghar on July 08, 2024, 10:01:56 amNot just that, so far I can not get any calibration information on my new meter from them or from the seller (Farnell UK). And I am not even sure where I could send the meter for calibration! (OK, calibration is simple and any decent calibration lab should be able to do it, however if the meter needs adjusting, it might be a problem) .Also the 3-year manufacturer's warranty on these meters is not transferrable from the original owner, so if you sell your meter or try to buy one second hand, there is no warranty even for a relatively new meter. Don't get me wrong, I like my DM7275 , use it all the time and won't swap it for almost any other meter, including the HP3458A, however the customer service from Hioki Japan is essentially non-existent and even from the distributor I can not get much sense so far in regard of calibration data.CheersAlex

author: HighVoltage
author_rank: Super Contributor
timestamp: July 08, 2024, 07:33:08 pm
content: I had tried a few times to the password from Hioki Japan but so far I had no luck.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 12, 2024, 02:12:38 pm
content: I've measured the DCV output of my HP3245A from -10V to +10V in 1V steps with the HIOKI DM7275. The measurements were made at 10V range, SLOW speed, 10 averages per point, with the input cables polarity reversed for the second run. Vset = voltage output setting on HP3245A, V = measured voltage with the correct polarity, Vr = measured voltage with the reversed polarity. V+Vr is the difference between measuring the same output voltage in two polarities. There is a small meter/cables offset about -2.5uV which I did not null. Vertical scale is 0.5ppm = 5uV per division.CheersAlex

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 13, 2024, 04:05:46 pm
content: And here is a 24h measurement run of 10V output from HP3245A, there is a visible tempco of about -0.5ppm/C for the two units and connecting wires. The room temperature (orange line) varied from 24.5C to 25.7C. Right now I'm running the same measurement for 1V output.CheersAlex

author: aronake
author_rank: Frequent Contributor
timestamp: November 26, 2024, 06:36:45 pm
content: Has anybody managed to figure out how to adjust a DM7275/DM7276 except for using the mentioned scaling hack?

author: aronake
author_rank: Frequent Contributor
timestamp: November 26, 2024, 06:41:56 pm
content: The adjustment menu is mentioned on page 203 in the manual. But they also say: "The adjustment screen accessible on the MENU > SYSTEM screen is used by Hioki for repair and adjustment purposes. It is not for customer use."www.itm.com/dm7276-01/manual/dm7276-01-manual.pdf?srsltid=AfmBOootKJ4X2_ElRKbZ8K__E4QlMGcIEXuv_FPCWucDw7tLfBVfxRff

author: nwind
author_rank: Regular Contributor
timestamp: May 17, 2025, 06:19:56 pm
content: Did anyone figure out what LTZ1000 temperature is set?

author: laichh
author_rank: Regular Contributor
timestamp: May 19, 2025, 04:14:00 am
content: Likely hiding behind the resistor network R4008.

author: nwind
author_rank: Regular Contributor
timestamp: May 19, 2025, 04:57:46 am
content: Would be quite interesting to know for long term stability

author: Andreas
author_rank: Super Contributor
timestamp: May 19, 2025, 05:44:00 am
content: R4008 looks to me as one resistor with 4 (2 pairs) of pins.The 1K resistor should be R4005.P4004 is the test point at the tap. (Setpoint voltage)with best regardsAndreas

author: laichh
author_rank: Regular Contributor
timestamp: May 19, 2025, 05:50:50 am
content: R4008 is an RM3225 resistor network by Susumu.https://www.susumu.co.jp/english/product/category.php?cid=2

author: nwind
author_rank: Regular Contributor
timestamp: May 23, 2025, 11:44:55 pm
content: Well, I did something really good or incredibly stupidI bought used DM7276-01 from Japan's used test equipment reseller on eBay for less than $1000Looks like it's working but he claims that he can't fully test it.He has 100% rating for quite a few sales though."Hello, and thank you for viewing this listing.This item is used.It was previously used in a factory, but I acquired it after the factory was shut down.Please note that due to my limited technical knowledge, I have not performed any detailed calibration or full functionality testing.For this reason, I am offering it at a lower price than the market average.Please understand this before making a purchase.Feel free to contact me if you have any questions."Considering his respond probably more in stupid category, but I can't resist and it was kind of impulsive purchaseI guess I'll find out in about a week.One of the problems is I don't have any reference to check it against, but have ADR1399 and ADR1001 dev boards and two 34465A plus 34410A to compare.Good thing is in case it's OK, then it should be well aged and very stable.🤞🏻

author: zepto
author_rank: Regular Contributor
timestamp: May 24, 2025, 03:33:50 am
content: Seems like a good deal. I bought an untested 7275 from japan with no ability to return. The only images showed it on but not sampling.It's sealed and has no fan, so you won't have to worry about it being dirty inside or someone running it with the fan flush against a wall. It's a pure dc voltmeter so it's sorta hard to damage with negligence. I wasn't worried at all and mine worked fine. The touchscreen interface is not my favorite, but it's an impressive instrument. It's also smaller than most meters.Looks like someone bought an open box 7276 on ebay for $750 (or maybe less). That is a steal considering what people are paying for new 6.5 meters. I never catch the good deals for Japanese equipment on ebay, but I've bought several things from Yahoo/Mercari.

author: nwind
author_rank: Regular Contributor
timestamp: May 24, 2025, 05:01:38 am
content: Time will tell it is... .7276 just open box for $750 it's a steal for sure

author: Rubo
author_rank: Regular Contributor
timestamp: May 24, 2025, 05:36:38 am
content: Quote from: zepto on May 24, 2025, 03:33:50 amThat was me

author: nwind
author_rank: Regular Contributor
timestamp: May 24, 2025, 03:08:10 pm
content: Quote from: Rubo on May 24, 2025, 05:36:38 amGood for you

author: nwind
author_rank: Regular Contributor
timestamp: May 24, 2025, 03:10:43 pm
content: There is Hioki related SW page:https://www.hioki.com/global/support/download/software?keyword=dM7276What out of this page is everyone used and how well it works?What are you using to collect data?

author: Rubo
author_rank: Regular Contributor
timestamp: May 25, 2025, 02:11:04 am
content: I was going to use the Hioki app, GENNECT One, but the firmware on mine is one version too old. FW version in it is 1.08, the app requires at lest 1.09I talked to Hioki USA and looks like it CAN NOT be updated by the end user. They don't even have it themself. From what I understood they have to ship it to JP.Had to fill out a form with the service department for them to let me know how much it is going to cost me to have it shipped to them for a FW update.Good news is, it will be a "free" upgrade with me only paying $25 return shipping fee. Just have to find time to send it in. Lead time is expected to be 4-6 weeks.Will ask them how much for a calibration (adjustment if needed) since it will be there for a while, might as well have a baseline for it.Technical support suggested this in the mean time : Sample Application(RM3544Series DM7275Series DM7276Series)It the second one from the bottom, but it requires a USB connection to the meter.Been using Test Controller and it been flawless logging from DM7276 & KS34465AHope this helps

author: nwind
author_rank: Regular Contributor
timestamp: May 25, 2025, 07:04:58 pm
content: Interesting approach to FW updates.Please share the info about cost related to ship it to Japan and calibration

author: nwind
author_rank: Regular Contributor
timestamp: May 28, 2025, 09:15:07 pm
content: Quote from: Rubo on May 25, 2025, 02:11:04 amDid you figure out how much is to ship/FW update/calibrate with Hioki?I just received mine.Looks good and appears to be fully functional but has even older FW (1.07).Interesting that it's disagreeing with both of my 34465A for ~10uV at 10V (technically 1ppm), but the same with 34461ACabling isn't ideal, but results don't change with different connection order.

author: Rubo
author_rank: Regular Contributor
timestamp: May 29, 2025, 06:12:22 am
content: Yes.FW upgrade is free in my case, I just have to pay $25 for return shipping.They have quoted me $75 for factory calibration "with Calibration certificate and Datasheet".I will double check with them what exactly they mean by that once they have the meter.May endup paying more for a traceable calibration.Been lucky that my meters are fairly close to each other (not that it means anything if they are all out

author: nwind
author_rank: Regular Contributor
timestamp: May 29, 2025, 05:09:47 pm
content: $75 sounds to me like a very reasonable price for calibration.Traceable one definitely even better.Did you contact Hioki USA through their website?Please keep us updated with info.I would for sure want to do proper calibration and FW update.Hioki should've not called it DMM since technically it's just a voltmeter, but so far I really like this little guyRun 3 of them for ~14 hrs with 100plc with statistics and despite they are ~30uV (6ppm) off Hioki has much less variations in measurement, looks more stable, and guess less noisy.Hioki - 5uVpp2x 34465A 20uV & 25uVPretty big difference.With small room temp variations (a few C), Hioki readings were very stable and both 34465A drifted slightly hence the difference above.All of them were connected to ADI ADR1001 dev board which looks to me more stable (as it should) than I thought before HiokiGoing to run again, collect data, and plot some diagrams.

author: nwind
author_rank: Regular Contributor
timestamp: May 29, 2025, 05:38:22 pm
content: Much better coherence with 34461A & 34410A at the first glance. Both 34465A are very close to each other, but looks like their scale is a bit smaller. Interesting.I'll let them warm-up and will collect data.

author: Rubo
author_rank: Regular Contributor
timestamp: May 29, 2025, 06:52:12 pm
content: Yes, I contacted Hioki USA through their website.They called me back within a day or so.Hioki do call it a voltmeter, it's right there on the top rightI'll keep you posted on what happens. Will be mailing it to them probably tomorrow.Latest plot showes 0.7ppm p-p over the span of 5C ( from 21.8 to 26.8 )While 34465A shows 1.9ppm over the same span.Most likely due to their respective references. LTZ1000 is much more stable compared to LM399

author: nwind
author_rank: Regular Contributor
timestamp: May 29, 2025, 08:01:26 pm
content: Thanks!Agreed about LTZ1000A vs LM399Looks like noise is better as well.With data collection what is interesting that 34410A provide measurements with 10nV resolution and Hioki is only 1uVWould be nice to have more bits from Hioki for better statistical analysis.

author: nwind
author_rank: Regular Contributor
timestamp: May 29, 2025, 11:28:42 pm
content: 10K 0V readings with 10plc, 200ms data collection interval

author: Rubo
author_rank: Regular Contributor
timestamp: May 29, 2025, 11:49:35 pm
content: What are you using for data collection?I've been using Test Controller and with both Hioki & 34465A I can get 100nV resolution (so 7 digits after 10).Not sure how accurate the readings from 34465A are at that point.If you try and request the 8th digit both meters just show 0 for it.Havent tried to log 34410A yet, don't think there's a definition file for it in Test Controller???

author: nwind
author_rank: Regular Contributor
timestamp: May 29, 2025, 11:54:08 pm
content: I'm using Hioki tiny USB collection for now and free version of Keysight SW.Keysight definitely recorded data down to 10nV resolution. Not saying it's accurate, but random noise is good for averaging/oversampling and better looking distribution diagram.

author: nwind
author_rank: Regular Contributor
timestamp: May 30, 2025, 12:01:48 am
content: Quote from: Rubo on May 29, 2025, 11:49:35 pmMost likely you can collect it as it it 34401A, and if not you can set 34410A to pretend to be 34401A

author: nwind
author_rank: Regular Contributor
timestamp: May 30, 2025, 12:53:49 am
content: Hioki & 34410 +/-5V

author: nwind
author_rank: Regular Contributor
timestamp: May 31, 2025, 03:03:48 am
content: Couple interesting graphsFirst one is 7276 vs. 34410A at overnight run with 100plc with ADR1001 5V VREFBesides some initial disturbance you can see how stable 7276 vs. small room temp changes and how much 34410 drifted.Second one is a day run for 7276 vs 34461A with AC at some point blowing at them (~2M distance). 7276 has some temp. variations, but 34461 is much worse.

author: Rubo
author_rank: Regular Contributor
timestamp: June 01, 2025, 12:48:25 am
content: That's about what my observations were (but my 34410A seems to be a little more stable than yours with temperature).DM7276 is on it's way to Hioki USA. They should get it monday.So my experiments will have to be put on hold until it comes back.I'll keep you posted

author: Simmed
author_rank: Frequent Contributor
timestamp: June 01, 2025, 01:59:26 am
content: could you perhaps try get a adev plot using the same data ?https://www.eevblog.com/forum/metrology/dmm-adc-noise-comparison-testing-project/msg2655327/#msg2655327Quote from: nwind on May 31, 2025, 03:03:48 am

author: nwind
author_rank: Regular Contributor
timestamp: June 01, 2025, 02:31:07 am
content: Quote from: Simmed on June 01, 2025, 01:59:26 amIt's a pretty long thread. What exactly you want me to do? I did some data collection with shorted input on 100mV range

author: VE2UM
author_rank: Contributor
timestamp: June 01, 2025, 05:54:54 pm
content: Hi....Outside of the LTZ1000A itself, the HIOKI DM7275 daughter reference board uses SMD resistors...Does anyone know what brand / model / series of SMD resistors are used for critical positions since the long term stability partially depends of these reisitors ( R1 to R5 in the original Linear Technology PDF ) ?Thank you.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 01, 2025, 06:32:06 pm
content: The resistor array for the temperature set point looks a lot like Susumu RM. Should be a custom ratio.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: June 04, 2025, 08:17:51 pm
content: A small update on my DM7275, I use it now for over a year and it has drifted about +5 ... +6ppm (so the reference voltage went down that much) according to both of my "main" 10V references (JVR and Fluke 731B) and my freshly calibrated and adjusted Keysight 34465AM. I will investigate a possibility to send the meter to Japan for calibration if that is the only way, however I would rather find a simpler option! I am really tempted to add an adjustment trimmer to the reference board!CheersAlex

author: nwind
author_rank: Regular Contributor
timestamp: June 04, 2025, 08:25:19 pm
content: What about using scaling?

author: Alex Nikitin
author_rank: Super Contributor
timestamp: June 04, 2025, 08:30:55 pm
content: Quote from: nwind on June 04, 2025, 08:25:19 pmI am already using it and that is a valid option. It is just the usual annoyance of something which is not perfect enough.CheersAlex

author: nwind
author_rank: Regular Contributor
timestamp: June 04, 2025, 08:34:58 pm
content: True, just trimmers stability always scares me )))

author: Alex Nikitin
author_rank: Super Contributor
timestamp: June 04, 2025, 08:39:07 pm
content: Quote from: nwind on June 04, 2025, 08:34:58 pmIf you pad trimmers enough, there is no problem, as my HP3456A proves.CheersAlex

author: nwind
author_rank: Regular Contributor
timestamp: June 05, 2025, 01:16:28 am
content: I guess it will work, but at the same time it should slow down aging and stabilize now, so perhaps just a resistor instead of trim pot.

author: Rubo
author_rank: Regular Contributor
timestamp: June 05, 2025, 04:44:30 am
content: Just an update.Got an email from Hioki USA that they received my meter yesterday and will be sending it to Japan on friday.I'll keep you posted

author: aronake
author_rank: Frequent Contributor
timestamp: June 05, 2025, 05:45:35 am
content: anybody been able to do own adjustment? Or adjustment password is not know?Quite terrible if any meter needing adjustment has to be sent to Japan.....

author: Rubo
author_rank: Regular Contributor
timestamp: June 05, 2025, 05:57:27 am
content: Just to be clear, they are not sending it to Japan for the calibration.They are sending it to Japan for the FW update.Calibration can be done locally.To answer your question, no, I have not heard or read of anyone doing adjustment to either 7275 or 7276.Since the meter had to be sent to Japan for FW update anyway, and since the price for calibration was fairly reasonable, I decided to have it done by the factory.After a year or so, if I have any doubts as far as it's readings, I'll revisit the topic of adjustment again.

author: nwind
author_rank: Regular Contributor
timestamp: June 05, 2025, 11:02:01 am
content: It'd definitely suboptimal, but ...Do you have any updates about cost for different options, i.e. traceable calibration, full call report etc?

author: Rubo
author_rank: Regular Contributor
timestamp: June 05, 2025, 01:07:03 pm
content: I agree. It is inconvenient to have to send it to Japan just for a FW update.Factory calibration was quoted at $75. Allegedly it will include a report (I will see what kind of report once I get it back).Haven't asked about other options since I don't realy need a traceable calibration right now.Hioki USA does offer it. I think they have 2 optionf for a traceable cal. Don't think it will be too expensive, it's only a voltmeter.Keysight charges between $323 (for Keysight calibration) & $612 (for a calibration with "Uncertainties and Guardbanding") for a 34465A.Can't see how just a voltmetrer can be anywhere close to a price of calibrating a full DMM.I would venture a gues it should be under $400 for a traceable cal.P.S. I know Keysight offers 3rd party device calibration. I'll ask them if they can calibrate DM7275 / 76 & how much they will charge for different options (if they can).When I hear back from Keysight, I'll post back (might be a while).

author: nwind
author_rank: Regular Contributor
timestamp: June 05, 2025, 01:18:58 pm
content: Thanks for all of the updates.Do you know if this $75 cal will include an actual report with the data, or just statement that it's calibrated?I was looking into Hioki manual for LAN connection and didn't see any DHCP settings like 34465 or similar. What is your experience guys? Do you have to choose a free IP address (my network has quite a few devices) and manually assign it into the unit?

author: Rubo
author_rank: Regular Contributor
timestamp: June 05, 2025, 03:05:09 pm
content: Accourding to Hioki USA, yes, it will include a calibration report. What kind of a report remains to be seen.The meters don't support DHCP. You have to assign IP address information manually.

author: nwind
author_rank: Regular Contributor
timestamp: June 05, 2025, 03:09:36 pm
content: Quote from: Rubo on June 05, 2025, 03:05:09 pmUnfortunate, but not a deal breaker.Probably the best to assign a permanent IP based on MAC address

author: Alex Nikitin
author_rank: Super Contributor
timestamp: June 05, 2025, 05:17:06 pm
content: Quote from: nwind on June 05, 2025, 01:18:58 pmYes, that what I did. I mostly control my Hioki over the Ethernet using a Python program which my son kindly wrote for me. It allows me to load a config file with most parameters (range, speed, number of readings etc) and writes the data into a .CSV file with exact timestamps, so I keep a number of such configuration files for common tasks (i.e. 10V range, 3600 data points at Medium speed and 0.5s intervals for a 30min acquisition)CheersAlex

author: nwind
author_rank: Regular Contributor
timestamp: June 05, 2025, 05:37:39 pm
content: In my case I will need to ask ChatGPT or Claude to do Python coding for me

author: Alex Nikitin
author_rank: Super Contributor
timestamp: June 06, 2025, 10:46:15 pm
content: Here is a couple of graphs made by using the DM7275 and my recently calibrated and adjusted Keysight 34465AM (modified with ADR1399) in parallel. 24h run at 5s intervals, measuring the 10V JVR reference (and the Hioki was measuring the case temperature of the reference as well).CheersAlex

author: nwind
author_rank: Regular Contributor
timestamp: June 06, 2025, 10:59:04 pm
content: First plot looks like almost exact replica just shifted by 60uV 😁Not sure what is the second one.I contacted Hioki USA for the FW update and calibration. Back and forth emails exchange.Hopefully more details on Monday.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: June 06, 2025, 11:14:36 pm
content: Quote from: nwind on June 06, 2025, 10:59:04 pmThe second is the voltage v temperature, also a good fit. Here is the plot of the difference between two meters, as you may see, there is a roughly 0.5ppm/C difference in temperature coefficients of the two meters (I suspect the Keysight is the main contributor). The combined noise is about 4uV p-p.CheersAlex

author: nwind
author_rank: Regular Contributor
timestamp: June 07, 2025, 03:52:03 am
content: From my very limited experience Hioki is the most stable for drift/temp and least noisy among with the bunch of my 6.5 multimeters.Looks like your 10V reference has some measurable temp coefficient.I've ordered Hioki temp sensor and received it while I was traveling. Flying home now, so I can test it soonWill be interesting to check Hioki against the rest of my other meters after FW update and calibration.I guess I can use it to calibrate at least DC voltage on most other multimeters after

author: iMo
author_rank: Super Contributor
timestamp: June 07, 2025, 07:57:02 am
content: Quote from: Alex Nikitin on June 06, 2025, 10:46:15 pmI've been planning the same w/ my 34401A - what is your result like compared to the original 399?

author: Alex Nikitin
author_rank: Super Contributor
timestamp: June 07, 2025, 11:48:11 am
content: Quote from: iMo on June 07, 2025, 07:57:02 amHere.CheersAlex

author: nwind
author_rank: Regular Contributor
timestamp: July 07, 2025, 12:59:29 am
content: Quote from: Rubo on June 05, 2025, 03:05:09 pmDid you get your calibrated meter back?You sent it out earlier than me

author: Rubo
author_rank: Regular Contributor
timestamp: July 07, 2025, 07:35:34 pm
content: Not yet.Last communication I had with them was on June 4th, they were going to ship it to Japan on that Friday (June 6th).Since they quoted me 4 to 6 weeks, I'll wait another week and ask them for an update.Will keep you posted

author: nwind
author_rank: Regular Contributor
timestamp: July 07, 2025, 08:25:42 pm
content: Thank you!I'm hoping to get mine back soon after you get your back.

author: Rubo
author_rank: Regular Contributor
timestamp: July 18, 2025, 06:13:26 am
content: Emailed Hioki earlier today.Allegedly they have sent me 2 emails on 07/02 & 07/08 to let me know that my meter is ready.I haven't received any emails from them (not even in junk/spam), so not sure what to say.Will give them a call tomorrow to pay for it, so they can ship it back.Quote from: nwind on July 07, 2025, 08:25:42 pmI would check with them to see if yours is ready also.

author: nwind
author_rank: Regular Contributor
timestamp: July 18, 2025, 01:04:16 pm
content: Thank you!

author: Rubo
author_rank: Regular Contributor
timestamp: July 24, 2025, 08:50:05 pm
content: Just got my DM7276 back.Hioki calibration included a full test report. Not bad for $75Looks like mine is 0.5ppm low on 10V (9.999995V actual reading).

author: nwind
author_rank: Regular Contributor
timestamp: July 24, 2025, 09:58:26 pm
content: I sent a few emails recently to Hioki USA inquiring about status of my meter and didn't receive any answers yet.A bit surprised since they were much more responsive before

author: nwind
author_rank: Regular Contributor
timestamp: August 06, 2025, 04:00:32 pm
content: Got it back yesterday finally.Looks quite good actually.~ -350nV offset at 100mV range with 100PLC and more or less uniformly higher gain on all ranges like 10.000018V at 10V, i.e. 1.8ppm

author: HighVoltage
author_rank: Super Contributor
timestamp: August 06, 2025, 05:04:22 pm
content: Quote from: Rubo on July 24, 2025, 08:50:05 pmCan you share your test report? (May remove all personal data)

author: Rubo
author_rank: Regular Contributor
timestamp: August 06, 2025, 05:16:32 pm
content: Very niceReadings on mine are:100mV range:Input Reading0mV 0.00000mV100mV 100.00003mV1000mV range:Input Reading0mV 0.0005mV1000mV 1000.0004mV10V range:Input Reading0V 0.000002V1V 1.000001V10V 9.999995V100V range:Input Reading0V -0.00002V100V 100.00008V1000V range:Input Reading0V -0.0004V500V 499.9991V1000V 999.9999V

author: Rubo
author_rank: Regular Contributor
timestamp: August 06, 2025, 05:19:08 pm
content: Quote from: HighVoltage on August 06, 2025, 05:04:22 pmDo you want me to scan it and post it?Do you want the equipment used page also?

author: nwind
author_rank: Regular Contributor
timestamp: August 06, 2025, 06:50:33 pm
content: I’ll post mine later today

author: nwind
author_rank: Regular Contributor
timestamp: August 07, 2025, 04:43:05 pm
content: Cal. results

author: nwind
author_rank: Regular Contributor
timestamp: August 07, 2025, 04:47:11 pm
content: In general should be easy to correct this small gain error with scaling. Looks like it holds with different ranges and both positive and negative inputs.I wish their Fluke calibrator wouldn't be at the end of it's cal period, but it is what it is

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 07, 2025, 10:22:10 pm
content: Quote from: nwind on August 07, 2025, 04:43:05 pmThank you, it was interesting to see the temperature calibration as well. I have a matching original HIOKI temperature probe (Z2001) for my DM7275, and was not sure how accurate the results are (the difference with my uncalibrated Fluke 80TK + a thermocouple was almost 1C !). Recently I've bought a class A PT100 temperature probe. 4-wire version, for my updated and calibrated Keysight 34465AM (which specified for PT100 as 0.05C + probe accuracy 0.15C = 0.2C error). I've joined two probes by a copper tape and run a temperature sweep in my reptile box. To my surprise the DM7275+Z2001 and K34465A+PT100 matched each other better than 0.05C even in dynamic conditions with temperature changes from 18C to 26C (two probes have a noticeably different thermal time constant, the Z2001 is much slower), with less than 0.02C difference in a settled state. Now I've calibrated my Fluke to match these two and happy with the results!The first graph is an overnight run (15h), starting about 17.5C with the box then powered off and slowly warming up to 26C. The second is a 12min section at 17.6C with the cooling cycling at 2min intervals. The green line on both graphs is the difference between two measured temperatures on the right scale at 0.01C per division.A somewhat strange shape of the differential curve is mostly due to the limited resolution of the HIOKI (0.01C) when the Keysight resolves 0.001C, combined with the difference in the time lag.CheersAlex

author: nwind
author_rank: Regular Contributor
timestamp: August 08, 2025, 12:06:08 am
content: I bought an original Hioki temp sensor right after I bought meter, so I hope it should be pretty accurate

author: nwind
author_rank: Regular Contributor
timestamp: August 08, 2025, 12:07:26 am
content: Thank you for posting your results Alex!

author: Rubo
author_rank: Regular Contributor
timestamp: August 08, 2025, 02:21:02 pm
content: Sorry for the delay, here is the report:

author: nwind
author_rank: Regular Contributor
timestamp: August 09, 2025, 07:42:30 pm
content: Not bad for about two days non stop.Pretty symmetrical as well.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 10, 2025, 10:32:59 pm
content: Here is my DM7275, with a 2m screened cable (Staubli plugs), shorted at the end, 100mV range, 24 hours run, the room temperature changed between 25.3C and 27.6C, about 2.3C. 100NPLC, 5sec intervals, Vp-p about 400nV over 24h, about 300nV inside 1h, 2min averaging takes it to <150nV p-p over 24h. Not nulled. From the look of it, the total offset tempco is about 50nV/C.CheersAlex

author: nwind
author_rank: Regular Contributor
timestamp: August 10, 2025, 10:41:41 pm
content: Looks good.I need to run proper data collection for both voltages and temperature.

author: Rubo
author_rank: Regular Contributor
timestamp: August 12, 2025, 05:17:59 am
content: Quote from: Alex Nikitin on August 10, 2025, 10:32:59 pmInspired by you, decided to do the same experiment. Short was a shorting pcb with banana plugs.Over 26 hours temp was between 22.18C & 28.69C. Vp-p of 530mV. I'm not good with creating charts, so just took a screenshot of TC.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 14, 2025, 06:36:01 pm
content: My son did write a Python program for me, to operate DM-7275/76 over a Telnet connection and collect the data to CSV files.Now this program is on GITHUB, as it might be useful for other users of these fine meters.CheersAlexP.S. - please note that I could not check all options and functions available in the HIOKITOOL program so some trouble should be expected. All functions I did check worked fine though.

author: nwind
author_rank: Regular Contributor
timestamp: August 14, 2025, 08:47:33 pm
content: Great!Thank you Alex and big thanks to your son!