What is the accuracy of your power supply!? - Page 1
Forum section: electronics / testgear

author: electroalchemist
author_rank: Newbie
timestamp: August 05, 2025, 05:39:24 pm
content: I attended Electronica in Germany last year and visited the booths of major power supply manufacturers including Keysight, BK Precision, Yokogawa, and Rohde & Schwarz. While testing some of their high-precision power supplies, I noticed the output voltage didn’t always align with what was displayed. For example, setting the output to 5.000 V measured accurately on a precision multimeter (Fluke 289), but when I set it to 9.876 V, the reading was off by 10–20 mV — well beyond what their datasheets claim. This discrepancy persisted even under load and with 4-wire sensing enabled.Has anyone else observed this kind of behavior? Do these devices get calibrated only at standard points like 5 V or 10 V? Shouldn't the accuracy hold consistently across the entire voltage range?I'm evaluating options for a high-precision power supply, but experiences like this are making me question how much trust to place in the datasheet specs. If you have any advice on how to evaluate and choose a trustworthy brand, I’d greatly appreciate it.

author: Aldo22
author_rank: Super Contributor
timestamp: August 05, 2025, 05:56:49 pm
content: Are you sure you measured that correctly?Even my Fnirsi DPS-150 "toy" power supply is better than that, even though it doesn't have 1mV resolution.

author: electroalchemist
author_rank: Newbie
timestamp: August 05, 2025, 06:19:03 pm
content: Thanks. At least your "toy" power supply doesn't claim sub-mV accuracy for >2kRegarding the measurements — yes, the multimeter I used is essentially a "gold standard" in the field. On the other hand, my BK Precision 9111 doesn’t deliver the level of accuracy its datasheet claims.

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 05, 2025, 07:22:23 pm
content: When was the Fluke last calibrated? Did you account for cable loss? If every expensive PSU you tested on the same meter was off, I'm going to go ahead and guess it's not so likely the PSUs at fault for the readings.The Fluke 289 TRMS best accuracy is +/- 0.4%; at 5V, that's 20mV.

author: nctnico
author_rank: Super Contributor
timestamp: August 05, 2025, 07:26:33 pm
content: It is possible the voltage setting DAC is 'only' 12 bit. So the PSU is accurate to it's setting but the steps are quite large.

author: Aldo22
author_rank: Super Contributor
timestamp: August 05, 2025, 07:29:04 pm
content: Quote from: KungFuJosh on August 05, 2025, 07:22:23 pmDC accuracy is 0,025 % + 2 afaics.

author: RoGeorge
author_rank: Super Contributor
timestamp: August 05, 2025, 07:51:26 pm
content: I have a Rigol DP832. Accuracy after calibration was 1mV or less, under the entire range 0..32V, 0..5.3V on all 3 channels.Similar for current, accuracy 1mA or better for the entire range, 0..3.2A. Specs resolution for DP832 is 1mV and 1mA.Mine is sensitive with temperature (used in a lab without AC, where the room temperature between summer winter can be about 10*C or so). Overall the accuracy is less than 3-5mV and 2-3mA, but never measured summer/winter variations, because to my use case the accuracy of a power supply is not such a big deal, as long as the output is stable and well regulated.

author: GigaJoe
author_rank: Frequent Contributor
timestamp: August 05, 2025, 08:16:34 pm
content: so ... out of curiosity ...BK precision , 9141 -> 0.03% + 8 mV ; for 9V it would be 2.5mV + 8mV ( but offset can be even bigger )cost US$ 2100( i probably can buy 20bit DAC\ADC , for DIY .. havin such a budget ... )

author: jonpaul
author_rank: Super Contributor
timestamp: August 05, 2025, 08:24:47 pm
content: We use the fine HP precision classic PS from 1980s:https://ia601701.us.archive.org/14/items/manualsbase-id-377055/377055_text.pdfAccuracy 0.025%0-100V 6115A0-40V 6114Aj

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 05, 2025, 09:01:45 pm
content: Quote from: Aldo22 on August 05, 2025, 07:29:04 pmMaybe at best, but also with a fresh calibration/adjustment. Like I said though- if every device disagrees with the measuring device, it's probably the measuring device or test setup or user error.

author: RoGeorge
author_rank: Super Contributor
timestamp: August 05, 2025, 09:30:45 pm
content: Forgot to write, for Rigol DP832 there are about 30 calibration points or so per channel, and there are 4 values to be measured/calibrated for each of these 30 points: the output voltage and output current vs the requested value, then the displayed current and voltage measured by the front panel of the PSU, too.In theory can be done manually, but in practice it will last hours to input that many values manually. Can be automated by an SCPI script to read the DMM, then write that into the DP832 PSU.DP832 is an analog power supply, decent specs and low noise for its price (~$800 ten years ago, don't recall the exact price). Still in production. 2 channels 0-32V/3.2A, and a 3rd channel 0-5.3V/3.2A. CH1 is floating, the other two have common ground. Has compensation wires for each channel, but they are tied internally. Other models from the same series have the compensation wires available externally.

author: tszaboo
author_rank: Super Contributor
timestamp: August 05, 2025, 09:36:43 pm
content: Quote from: electroalchemist on August 05, 2025, 05:39:24 pmNone of them will be very good without 4 wire measurement. There are models from ie TTI for a few hundred EUR, that has that, and offer mV resolution.They make PSUs which have 6.5 digit readback accuracy, and SMUs that might have even more. It's all question of how much money you have.

author: Martin72
author_rank: Super Contributor
timestamp: August 05, 2025, 09:42:41 pm
content: At work, there is almost nothing that is not calibrated.One of the exceptions is power supplies, because we always set their current and voltage with a calibrated multimeter.I have adopted the same practice at home, where it makes sense to set the values with a multimeter.If I know that the circuit to be supplied generates its own internal voltages anyway, it is sufficient for me to look at the power supply display.Whether the circuit then receives exactly 5V or 5.1V, for example, is completely irrelevant.

author: mawyatt
author_rank: Super Contributor
timestamp: August 05, 2025, 10:06:27 pm
content: Quote from: Martin72 on August 05, 2025, 09:42:41 pmWe used to do the same with our lab supplies before retiring, and way back we had "precision lab versions" recall from Power Designs if a precision voltage was required. In our home lab we have some SPD3303X (3), GPP4323, KWR102 and KWR103 labs supplies we use most and some no names for HV needs.After calibration we've found the SPD and GPP to be good enough that we don't check them unless we need a really accurate setting, then the DMMs are put to use. Even the Korads are pretty good altho we tend to check them more often as they are "switchers" which we try and avoid unless necessary.For awhile we checked everything from past experience, but have gained enough confidence in these supplies now.We know, Murphy is setting us upBest

author: nctnico
author_rank: Super Contributor
timestamp: August 05, 2025, 10:07:44 pm
content: Quote from: Martin72 on August 05, 2025, 09:42:41 pmThat is a cumbersome way of working. For my bench I specifically bought a PSU (Keysight) with accurate voltage and current reading so I don't need a DMM to check the readings. I was getting very tired of doing that. In addition, the current measurement is hard to do with a DMM due to burden voltage.

author: Martin72
author_rank: Super Contributor
timestamp: August 05, 2025, 10:35:24 pm
content: As you correctly pointed out earlier, the resolution of many power supplies is rather coarse.Accordingly, the combination of a calibrated multimeter and a medium-quality power supply is considerably cheaper than a power supply that no longer needs a multimeter to set it to the exact mV.The inevitable current fault measurement circuit when using a multimeter for current measurement in series is negligible, at least in our cases.

author: bdunham7
author_rank: Super Contributor
timestamp: August 05, 2025, 11:49:09 pm
content: Quote from: nctnico on August 05, 2025, 10:07:44 pmWith non-precision supplies the probem is that even if you dial them in to the last digit, they'll just drift away in 20 minutes anyway. My old Precision Designs 5020 is pretty good if I let it warm up--overnight! But it also does not even meet it's own specs for accuracy according to the front dials so I have to trim it manually. The rest of the one I have are accurate enough for battery charging.

author: bdunham7
author_rank: Super Contributor
timestamp: August 06, 2025, 12:04:09 am
content: Quote from: KungFuJosh on August 05, 2025, 09:01:45 pmJust for a data point I pulled out my 289--last calibrated in May of 2022--and gave it exactly 5V and then 9.876V the back to 5V. Initially 5V read as "4.9997" (on the 5V range) and 9.876V read as "9.876" on the 50V range. Going back to 5V gave me "5.000", it stayed in the 50V range on the way down. A 189 last calibrated eons ago gave similar results, 4.9998/9.876/5.000. These meters are not going to read 20mV off @10V unless they are broken, no "fresh calibration" required. If the different PSUs were all off by the same amount in the same direction, I'd agree with you that the meter was broken. But the OP didn't say that.

author: Songhua
author_rank: Contributor
timestamp: August 06, 2025, 12:22:52 am
content: I have an old used DP832 which was calibrated recently. And precision was alright within its specs. The CH2 and CH3 share the common ground, but Rigol did the shorting using a very tiny wire inside the PSU. The new DP832 being sold is still having this design. I open the panel andsoldered a 10AWG wire on the CH2 GND and CH3 GNDso that when the DP832 is carrying load, the voltage drop on CH2 and CH3 won't be so significant due to the tiny voltage drop of the 10AWG wire.As for the OP's question,Check1. Whether Fluke 289 is calibrated2. Whether the PSU is calibrated3. Temperature might lead drifting4. Check the wires and connectors5. Before testing, it's better to warm up the PSU and multimeter for at least half a hour. Fluke 289 doesn't need because it's handheld multimeter.

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 06, 2025, 12:49:06 am
content: Quote from: bdunham7 on August 06, 2025, 12:04:09 amBroken might be a stretch, but certainly out of cal. To me, his statement read that he was frustrated by multiple devices from multiple brands, all tested with...the same meter. Perhaps I misunderstood, perhaps not. 🤷

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 06, 2025, 02:08:25 am
content: Hi,The HP 6554A, 60V, 9A power supply that I have on my bench is very accurate. Here are the measurements of the output voltage using a Fluke 8842A:The HP 6554A uses some good components to achieve this performance.The reference is an LT1021-10 and the op-amps in the DAC circuit are LT1001.The DACs are 12 bits, they are marked 7545 on the schematic. They could be AD7545 or LTC7545A.Regards,Jay_Diddy_B

author: EEVblog
author_rank: Unknown
timestamp: August 06, 2025, 02:50:48 am
content: Best PSU I have, the NGA100 shows 9.998V for 10.000V set. 0.01% + 5mV spec

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 06, 2025, 03:26:24 am
content: Call me crazy, but I'm quite content with the accuracy of my SPD3303X. The DAQ6510 was calibrated earlier this year.Thanks,JoshETA: Added a longer sample with stats.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: August 06, 2025, 03:39:06 am
content: Yesterday I saw the unboxing / initial review of Defpom's new 4 channel power supply. It's also off by some varying digits, so there is a bit of linearity difference.A "precision power supply" is no SMU yet. That adds a few digits to the price too.There is always a cost / benefit tradeoff. Even with sense lines power supplies will have some voltage drop due to copper resistance, and that can only be remedied by not drawing current at all. And then you get into the area of the voltage (current, multi) calibrators such as the PDVS2mini or that blue thing Dave stumbled upon years ago.

author: electroalchemist
author_rank: Newbie
timestamp: August 06, 2025, 03:56:12 am
content: Let's assume we have a power supply capable of sourcing with accuracy better than 0.1 mV and measuring voltage with accuracy better than 0.01 mV. I'm curious about the practical impact of such precision — specifically, who would typically require or benefit from this level of accuracy? Audiophiles readily invest in premium headphones for superior sound quality; similarly, is there an equivalent community/industry of "accuracy-philes" who value ultra-high-precision measurement equipment?

author: bdunham7
author_rank: Super Contributor
timestamp: August 06, 2025, 04:00:03 am
content: Quote from: electroalchemist on August 06, 2025, 03:56:12 amUm, yes. You've found it.Regarding a question raised about your OP; were the deviations from the expected value of the various PSUs off by some consistent amount and direction or were they random and in both directions?

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 06, 2025, 04:09:27 am
content: Quote from: electroalchemist on August 06, 2025, 03:56:12 amYes, this section of the site...but it gets worse if you go to the Metrology section:https://www.eevblog.com/forum/metrology/

author: electroalchemist
author_rank: Newbie
timestamp: August 06, 2025, 04:15:48 am
content: Thanks. I'd say the behavior seemed random. For instance, I specifically remember the Rohde & Schwarz was quite odd — when I set it to 1 mV (the smallest resolution) and turned the output on, the voltage ramped up to around 15 mV and went down.

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 06, 2025, 04:34:00 am
content: Quote from: electroalchemist on August 06, 2025, 04:15:48 amThat's actually common. There's a thread here somewhere where we compared the startup spikes on different power supplies.ETA: Found it:https://www.eevblog.com/forum/testgear/lab-power-supply-turn-on-and-off-characteristics/

author: Aldo22
author_rank: Super Contributor
timestamp: August 06, 2025, 09:07:41 am
content: Quote from: KungFuJosh on August 05, 2025, 09:01:45 pmYou're not seriously telling me that a $1000+ Fluke is off by 20mV at 5V when it hasn't been freshly calibrated?That would be far outside the specification.None of my cheap DMMs (ZT-225, AN870, CM2100B, AN8008) deviate more than 3 mV (or 3 digits) from 5 V, even after years of use, and they have never been readjusted since leaving the factory.

author: chilternview
author_rank: Frequent Contributor
timestamp: August 06, 2025, 10:31:16 am
content: Quote from: electroalchemist on August 05, 2025, 05:39:24 pmWhat is the expected use of a 'high precision' PSU? There are things like the Keithley 2400 series SMUs which may fit the bill, assuming you have deep pockets. I wouldn't expect a general purpose PSU to fall into the 'high precision' category though.

author: nctnico
author_rank: Super Contributor
timestamp: August 06, 2025, 11:08:56 am
content: Quote from: electroalchemist on August 06, 2025, 03:56:12 amFor powering a circuit 10mV accuracy / stablity is good enough. But if you want to provide a stable DC offset to a circuit, then stability is going to play a big role. But there are affordable (used) lab power supplies with excellent stability. Search for 'poor man's SMU' on this forum to find the Agilent 66311. Due to its 12bit ADC/DAC the control steps are coarse (4mV-ish) but the stability of this PSU is excellent.

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 06, 2025, 03:26:27 pm
content: Quote from: Aldo22 on August 06, 2025, 09:07:41 amI don't care how much a pretty grey and yellow toy costs. If you (hypothetically) measure 10 high-precision, high-end devices with it, and all 10 devices are off, it's probably not the 10 devices. As I said: test device, test setup, user error. Those are your options. I guess if the temperature is off far enough, that won't help either. Let's call that part of test setup.

author: Aldo22
author_rank: Super Contributor
timestamp: August 06, 2025, 04:03:47 pm
content: Quote from: KungFuJosh on August 06, 2025, 03:26:27 pmThat's not my point.I wanted to know whether I can trust a $1000 Fluke, or whether, as you said, it can be off by as much as 20mV on 5V under “normal” conditions.Is that really possible or even likely?

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 06, 2025, 04:36:24 pm
content: Quote from: Aldo22 on August 06, 2025, 04:03:47 pmOf course- shit happens.Did somebody drop it down the wrong flight of stairs? Did it fall down an elevator shaft on to a bunch of bullets? Who knows. Maybe some part failed, or maybe it drifted over time if it's really old, etc. Fluke is not infallible. The price tag doesn't tell you anything, especially not when it's a Fluke. Fluke comes with a premium price tag, and what that really means is debatable.Trust only what you can verify. That starts with calibration, but even a calibration can't rule out user error.

author: nctnico
author_rank: Super Contributor
timestamp: August 06, 2025, 04:55:36 pm
content: Quote from: Aldo22 on August 06, 2025, 04:03:47 pmAnything can break. I've seen US $250 dollar DMMs giving wrong readings due to the battery being a bit low.

author: AVGresponding
author_rank: Super Contributor
timestamp: August 06, 2025, 04:56:14 pm
content: Applying Occam's Razor, the likely explanation has already been hinted at by nctnico; the set voltage on these supplies will not always match the actual output due to granularity caused by the ADC.It does not matter that they are linear; the control is digital.

author: tggzzz
author_rank: Super Contributor
timestamp: August 06, 2025, 05:24:31 pm
content: Does nobody read test equipment specifications any more? Is that soooo 20th century?!There's absolutely no point is saying "is this (in)accuracy OK" unless it is compared with the specified accuracy.For a power supply the "accuracy" is - in many but not all cases - not a well defined figure. Consider a PSU supplying 1A through leads with a 0.1ohm resistance, i.e. a 100mV drop along the leads. Where do you measure the voltage? That's whysomePSUs have four wires: two for the current and two to sense the voltage at the far end of the wires.A power supply probably won't be low noise, especially if it is a switching supply or has a particularly noisy source. How will the noise (ripple, impulsive) affect the measuring equipment and/or any UUT?A power supply probably won't be a stable voltage, but will change with temperature, applied load, time, etc.There are exceptions to that. My Power Designs 2020 has an LM399 as the internal reference, can be set "digitally" to 1mV and has a potentiometer with a 1mV full scale range. For short term measurements, I can set the voltage to 20µV, but it will drift maybe 50µV over the course of an hour.As several people have noted, the usual way to use a power supply to define a voltage is to use a meter to measure the actual voltage at whatever points in the circuit are relevant, and twiddle the controls until the desired voltage is obtained. See, for example, how I use my PD2020.

author: chilternview
author_rank: Frequent Contributor
timestamp: August 06, 2025, 05:28:26 pm
content: Out of interest I just checked my Keithley 2231A psu. Set it to +15.00v and -15.00v and connected to a test circuit that drew about 40mA from each channel.Then hooked up two 34401A's to measure at the PSU outputs. They read +15.002v and -15.003v, which is better than I expected.

author: mawyatt
author_rank: Super Contributor
timestamp: August 06, 2025, 05:34:41 pm
content: Believe many of the modern "Digital Displayed" supplies operate in an "analog control loop" where the Reference the loop is working too is from a DAC, thus a Discrete level as the desired command parameter. So the actual "control loop" is linear and not digital whereas the command level is digital. They utilize an ADC to measure the output and use that as a Displayed Measured Value along with the Set Value.During Calibration, one creates a desired Set Value, then measures with an external accurate DMM and notes the ADC Displayed value. This is repeated over the PS range and recorded. Once Calibration is complete the values are used to create a table for error correction by means of simple linear interpolation.Anyway, this is the way we see our Power Supplies operating and the behavior of the user Set value and the ADC measured Output value.Best

author: bdunham7
author_rank: Super Contributor
timestamp: August 06, 2025, 05:52:19 pm
content: Quote from: KungFuJosh on August 06, 2025, 04:36:24 pmYes, but experience teaches us that some shit happens a lot more often than some other shit. There was a thread a few years ago where someone had a brand new SDM3065X that would drift during warmup and the unfortunate user was roasted for, among other things, comparing its readings to an old Fluke 189. Returning it to Siglent initially got a similar amount of scorn, but indeed it turned out to be a defective new SDM3065X.We still don't know exactly what discrepancies the OP was seeing other than the two that he stated so it is hard to judge just by the pattern. As you say, anything is possible and some of us have the luxury of having easy options to confirm the accuracy of a handheld meter. But realistically, based on experience, if I see a discrepancy like that I'd consider the probability that my 289 has suddenly failed in a way that it is out of spec but not obviously broken to be pretty low. Of course the same doesn't apply to an instrument I just picked up and haven't seen before, so if the OP just purchased the 289 yesterday at a rummage sale, then all bets are off.

author: Aldo22
author_rank: Super Contributor
timestamp: August 06, 2025, 06:14:10 pm
content: Quote from: bdunham7 on August 06, 2025, 05:52:19 pmThis does not have to be a luxury. A AD584LH reference is very inexpensive and sufficient to detect suspicious deviations.Quote from: bdunham7 on August 06, 2025, 05:52:19 pm+1

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 06, 2025, 06:22:39 pm
content: Quote from: Aldo22 on August 06, 2025, 06:14:10 pmTrue, but it depends on how deep you want to dive down that rabbit hole. I had one of those, but the value drifts significantly with room temp. I went through a bunch of refs before I landed on the VREF10-001 r9. That was as deep as I was willing to dive.

author: Aldo22
author_rank: Super Contributor
timestamp: August 06, 2025, 06:39:43 pm
content: Quote from: KungFuJosh on August 06, 2025, 06:22:39 pmI have never noticed this, but this may be due to the fact that my room temperature fluctuates by a maximum of 4°C.I think this simple reference would be sufficient to detect a deviation of 10-20mV from 5V discussed here.

author: bdunham7
author_rank: Super Contributor
timestamp: August 06, 2025, 06:52:29 pm
content: Quote from: Aldo22 on August 06, 2025, 06:14:10 pmChecking the meter at one point only guards against certain types of errors, mostly reference drift or similar issues. Maybe loss of calibration data as well. In this case the meter in question could plausibly be accurate in the 5V range but be off in the 50V range where the upper reading is. There could be a linearity issue as well, but that's less likely. Or input circuit damage that leads to leakage above 9.2V, and so on.However, a basic meter checking doesn't necessarily have to involve precision references. A cross-check with a known "good enough" source is also helpful. For example, my SDG2042X-H AWG provides DC offset and ACV signals that are accurate enough for the specs of most handhelds and with enough short-term stability to test many bench meters using a better one in parallel.

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 06, 2025, 06:55:31 pm
content: Quote from: Aldo22 on August 06, 2025, 06:39:43 pm4°C is plenty if your meter has enough digits.Aside from that, see bdunham7's note above.

author: Aldo22
author_rank: Super Contributor
timestamp: August 06, 2025, 07:18:53 pm
content: Quote from: KungFuJosh on August 06, 2025, 06:55:31 pmI don't have a 50000+ counts DMM, so the reference is sufficient for me.If I ever get a better DMM, I might also buy a better reference.It just has to match.

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 06, 2025, 07:20:00 pm
content: Quote from: Aldo22 on August 06, 2025, 07:18:53 pmLike I said, how deep do you want to dive?

author: armandine2
author_rank: Frequent Contributor
timestamp: August 06, 2025, 07:21:19 pm
content: Quote from: electroalchemist on August 05, 2025, 05:39:24 pm...at least two of my eight+ bench type power supplies have those sense wire terminals. So far I have never used that facility - I've not had the need for that kind of "precision".Having said that, I have used a process calibrator in that "more precise way".

author: Aldo22
author_rank: Super Contributor
timestamp: August 06, 2025, 07:32:08 pm
content: Quote from: bdunham7 on August 06, 2025, 06:52:29 pmSure. As mentioned earlier, even a DPS-150 can be sufficiently accurate up to approx. 30V.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 06, 2025, 07:55:31 pm
content: electroalchemist,I don't think that you have told the group what kind of voltage and current you are looking for?Most power supplies will use a 12-bit DAC. This allows the voltage to be set in 4096 steps from 0 to maximum.Voltage calibrators, like the Datron 4000A shown here, have many more bits and many precision components to achieve ppm accuracy levels. The Datron has 7.5 digits 0 - 19.999999, over 24-bits.There would be little point in using this as a power supply. Most circuits are designed to reject power supply variations.This used to calibrate meters.Jay_Diddy_B

author: tszaboo
author_rank: Super Contributor
timestamp: August 06, 2025, 09:31:33 pm
content: Quote from: Martin72 on August 05, 2025, 09:42:41 pmISO9001 calls for calibration for the power supplies that are used in production. So we calibrate them, in house, once a year. Takes like 30 minutes, once I crossed out all the unnecessary parts. They were asking for a bunch of shunts and whatnot to calibrate it, I just connect it to a DC load and dial up all the numbers, measure noise, and verify everything.Quote from: nctnico on August 06, 2025, 04:55:36 pmExactly, Or someone dropped it on the floor and it doesn't work properly in some ranges. Or the input connector is loose.The purpose of calibration is not only to figure out if the 10V is 9.99 because of drift, it's more fundamental than that.

author: tszaboo
author_rank: Super Contributor
timestamp: August 06, 2025, 09:32:47 pm
content: Quote from: Aldo22 on August 06, 2025, 07:32:08 pmMeasure it under full load, and see if the noise figure is according to the datasheet.

author: Aldo22
author_rank: Super Contributor
timestamp: August 07, 2025, 09:14:53 am
content: Quote from: tszaboo on August 06, 2025, 09:32:47 pmThe context here was to have a “sufficiently good” reference to detect significant deviations/errors in a DMM.This has nothing to do with noise under full load.Quote from: nctnico on August 06, 2025, 04:55:36 pmI always thought that you buy expensive DMMs so that this kind of thing can't happen...

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 07, 2025, 03:22:58 pm
content: Quote from: Aldo22 on August 07, 2025, 09:14:53 amIs $250 expensive for a DMM?

author: Aldo22
author_rank: Super Contributor
timestamp: August 07, 2025, 03:35:17 pm
content: Quote from: KungFuJosh on August 07, 2025, 03:22:58 pmFor a handheld DMM? For me, yes.I don't even know what would justify that price for me.I don't need expensive 1000V fuses.

author: nctnico
author_rank: Super Contributor
timestamp: August 07, 2025, 07:41:48 pm
content: Quote from: Aldo22 on August 07, 2025, 09:14:53 amOnly if you buy them from reputable brands like Fluke, Keysight, etc. Not overpriced stuff from BK precission.