7.5 digit bench DMMs comparison

[ebclr]

Do i also need a temperature and humidity controlled room in my home to do this high level hobby, perhaps some transfers standards, Sorry this isn't hobby this is NIST research department

[tautech]

ebclr
High resolution DAC/ADC testing, voltage references design and experimenting, ratiometric measurements (e.g. bridges, comparators). How these areas fill into home hobby? Well, that's a question outside of the choosing DMM here. It's often not resolution what justify such instruments, but their stability and accuracy. But that's only if 7.5/8.5 meter is tested and calibrated. Otherwise calibrated 6.5-digit meter in such cases often provide better accuracy than uncalibrated unknown 8.5-digit one.

Quite so.
I hear Chinese whispers a 6.5 digit model is not too far from the marketplace.

[HighVoltage]

Do i also need a temperature and humidity controlled room in my home to do this high level hobby, perhaps some transfers standards, Sorry this isn't hobby this is NIST research department

Well, a 7 1/2 digit multimeter will give you some good resolution for temperature measurement.
My new Keithley DMM7510 shows 4 digits after the decimal point.

I had a very good Fluke probe sitting in a bottle of water that was at equilibrium with the room temperature for a few days already.
The probe needed some hours to settle until only the last digit fluctuated.
Then I took a LED flashlight from about 1 m away and pointed it at the PT100 sensor inside the water bottle
And the last digit started to climb
Pretty amazing to see this.

Here is a first screen shot, just figured out to use HOME and ENTER simultaneous to get a screen shot to the USB stick.
(Why can the Keysight 34470A not have this cool feature)
 

[Dwaine]

Do i also need a temperature and humidity controlled room in my home to do this high level hobby, perhaps some transfers standards, Sorry this isn't hobby this is NIST research department

Well, a 7 1/2 digit multimeter will give you some good resolution for temperature measurement.
My new Keithley DMM7510 shows 4 digits after the decimal point.

I had a very good Fluke probe sitting in a bottle of water that was at equilibrium with the room temperature for a few days already.
The probe needed some hours to settle until only the last digit fluctuated.
Then I took a LED flashlight from about 1 m away and pointed it at the PT100 sensor inside the water bottle
And the last digit started to climb
Pretty amazing to see this.

Here is a first screen shot, just figured out to use HOME and ENTER simultaneous to get a screen shot to the USB stick.
(Why can the Keysight 34470A not have this cool feature)

Stop it....  I'm drooling.....   Every hobby Lab should have a DMM7510.....

[ebclr]

Based on the resolution of the temperate you are reading  I assume you are using a quantum mechanics sensor otherwise all those digits except the first 2 is a lot on nonsense number

[tggzzz]

Right now I have one bench DMM, the Rigol DM3068, but the device was not able to fulfil the following tasks I actually encountered:

- Measuring current flow of 10nA failed. Too noisy.

- Measuring current consumption based on cap discharge hardly works. I don't trust the results. The problem is DC Bias. I also encountered the phenomenon that the unconnected DMM set to 10G input impedance rises on voltage 1V/s. Looks like DC Bias as well. Of course this does not happen with 10M, but I can't use 10M for this task as it would bias the measurement. I use 10G for this.

Neither of those requirements implies need for a 7.5 digit resolution.

The "10nA" implies amplification before measurement. Of course that will directly expose fundamental measurement problems (e.g. noise, thermal and acoustic effects, maybe even number of electrons/s...) that can't be solved by a higher resolution measurement.

The "DC bias" issue implies you have a very high source impedance, which has other knock-on consequences.

[e61_phil]

Right now I have one bench DMM, the Rigol DM3068, but the device was not able to fulfil the following tasks I actually encountered:

- Measuring current flow of 10nA failed. Too noisy.

Did you try measuring 10nA in 100mV range with 10Meg input imepdance?

[bson]

For a cheap lab with cal instruments suitable for 6,5 digits dmm this will already cost you the price of half the new meter (400-500) ,

I paid $99 to have the 34465A calibrated after a year.  There is nothing to adjust - all that's done is installing of the new calibration data, which is automatically done by the calibration process, to compensate for drift.  I'm not aware of any modern DMM with anything to adjust; it's going to measure whatever it measures, and if it's out of spec (so far off the measurement can't be used for a linear reading based on calibration data) it needs to be repaired.

[Kjelt]

I paid $99 to have the 34465A calibrated after a year.  There is nothing to adjust - all that's done is installing of the new calibration data, which is automatically done by the calibration process, to compensate for drift.  I'm not aware of any modern DMM with anything to adjust; it's going to measure whatever it measures, and if it's out of spec (so far off the measurement can't be used for a linear reading based on calibration data) it needs to be repaired.

That depends on the calibration service. Normally they only measure your meter against known standard references and print out the deviation from those reference, they do not adjust anything, they just give you a piece of paper stating how much your meter deviates. That costs here in Europe between €140 and €300

If you want that they adjust your meter to the reference, then they measure the deviation, adjust and measure again the deviation, this costs twice or sometimes even more.
I know that in the US there are more cal labs and also cal labs that charge way less than here in Europe. For $99 measuring and adjusting would be an absolute bargain.

[HighVoltage]

I just spoke to Keithley Germany about the DMM7510 and also asked about calibration.
The guy quoted me Euro 330 over the phone (without adjustment) plus VAT and 1 week turnaround.
If adjustments are needed it will cost much more, depending on the adjustments, he said.

[bson]

That depends on the calibration service. Normally they only measure your meter against known standard references and print out the deviation from those reference,

I take my instruments to a well-regarded used equipment vendor in Santa Clara who regularly sends batches of equipment off to a local lab for calibration.  I find out when the next shipment is and drive down there, and drop it off.  I don't pay for a full report, only the standard NIST traceability certificate, and on return can verify that the calibration data has been updated both from the updated calibration date and from the fact that the readouts differ for my DMMCheck.  Since the readouts differ and there is nothing to adjust it implies there is new calibration data installed.  It's even possible the 34465A won't permit setting the calibration info string without also installing calibration data - some makes and firmware won't permit this.

They charged $150 for my Keithley 2001 (7.5d) two years ago if memory serves.  This is all quite cheap.

A lab that only compares the displayed readouts to a standard is worthless.  Proper calibration procedures for DMMs follow a specific SCPI based script that both validates measurements are within specification and installs new calibration data.  If they don't have the software to do this I'd go somewhere else, but any decent lab will.

[kj7e]

I have the Keysight 34470A for a while now and like it a lot for my VoltNuts addiction.
The calibration of this one is 1 1/2 years old

Now I have brand new Keithley DMM7510
This one was calibrated in 8/2016

In the next few days I will make some comparison measurements between the two.
But so far I see the following on my LTZ1000A reference:
The 34470A reads about 18 uV high
And the DMM7510 is about 20 uV low

What is really impressive with the 7510 is how quick it is warmed up to show a stable reading.
I have not measured it, but it is less then one minute, it seems.

Both instruments are recommended.
The handling is just very different.

If you are in to low current measurements, the 34470 has a 1 uA current range and the DMM7510 has a 10 uA current range.
And the 34470A is just amazing, in measuring this low current.
I have not tested this on the Keithley meter.

I've noticed this too, it only takes about 3 min to stabilized to sub PPM levels.  Here, I powered mine on with my 10v reference already fully stabilized.

Overall, from cold startup to 8 min;




First 90 seconds zoomed in;


Reaching 2 min mark;


Final stabilization;

[HighVoltage]

I've noticed this too, it only takes about 3 min to stabilized to sub PPM levels.  Here, I powered mine on with my 10v reference already fully stabilized.

It is truly amazing, how fast the DMM7510 will stabilize after a coldstart.
And you do not need to use the ACAL feature of the 7510, to get reliable readings.

[Kleinstein]

The jagged curve suggests that the 7510 uses some periodic corrections to compensate for drift about every 2 seconds. This could be temperature measurements and numerical corrections or maybe short adjustment cycles for the ADC gain (so kind of a partial ACAL).

In the 10 V range there is no need for that many parts to stabilize: its mainly the reference and some amplifier offsets to a point that the internal corrections / AZ works. The 1 V or 0.1 V range might need considerably more time.

The slightly larger jump at about 80 seconds looks a little odd. If such a jump (around 20 µV, if a judge the scales right) would happen in the more normal working range it could be really bad. It looks like those corrections also show some errors/noise.

[HighVoltage]

Here is a good comparison of a Keithley DMM7510 and a Keysight 34470A
Both hooked up to a 10V reference

[kj7e]

The slightly larger jump at about 80 seconds looks a little odd. If such a jump (around 20 µV, if a judge the scales right) would happen in the more normal working range it could be really bad. It looks like those corrections also show some errors/noise.

The bump at 80 sec was me disturbing the unit, power on default is 10M input and 1 NPLC, I switched it to Hi-Z and 2 NPLC.

[kelemvor]

Dragony, did you ever come to a decision?  If so, what did you go with?  I'm in a similar boat.  I want to buy a nice 7.5-digit meter for my home hobby lab, and I'm hoping someone's already done the work of comparing these devices.  I don't want to pay such an extreme price and then immediately wish I'd gone with a different one.

[tautech]

.......... for my home hobby lab, and I'm hoping someone's already done the work of comparing these devices. I don't want to pay such an extreme price and then immediately wish I'd gone with a different one.

Pick another hobby.

[mendip_discovery]

Go 8.5 and be done with it.

[tomud]

.......... for my home hobby lab, and I'm hoping someone's already done the work of comparing these devices. I don't want to pay such an extreme price and then immediately wish I'd gone with a different one.

Pick another hobby.

You are cruel   

Go 8.5 and be done with it.

 

[tautech]

.......... for my home hobby lab, and I'm hoping someone's already done the work of comparing these devices. I don't want to pay such an extreme price and then immediately wish I'd gone with a different one.

Pick another hobby.

You are cruel   

You think.

I developed some fascination with VNA's that a SVA1015X solved for a while but was replaced with a SVA1032X and now supplemented with a $14k 4 port SNA5004A.
That's nearing $20k invested in 2 great instruments to support my hobby.........

[tomud]

You think.

I think...

...thinking about buying the SNA5012A for hobby purposes 

[tautech]

You think.

I think...

...thinking about buying the SNA5012 for hobby purposes 

My SNA5004A magically became SNA5104A 
But better is coming..... VNA 2 and 4 port models to 26.5 GHz   

[mawyatt]

Well we got three KS34465A and put them in series for a 19 1/2 digit DMM 

Here we are measuring our calibrated AA cell at 0.52897705273240526222 volts 

Darn AA cell must be dead 

Best,

[DavidKo]

You are doomed. IKEA no longer produces alkaline cells.

@tautech: you can try photography, cycling etc.  instead of electronics , sometimes it may be cheaper