Author Topic: What you use benchtop 5.5digit+ DMM for?  (Read 15388 times)

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Offline bitseeker

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Re: What you use benchtop 5.5digit+ DMM for?
« Reply #50 on: August 29, 2016, 07:12:13 pm »
So, if you have to buy another DMM, might as well buy one of the benchtop variety.

Why? Because you can't explain to the missus you need two times the same instrument. A bench DMM looks like something different entirely  :-DD

Ah, well, that depends. If the missus has two or more of anything in different colors, then you can do the same with handheld DMMs. e.g.,

Greenlee = green DMM
Keysight = orange DMM

Different = win! :-DMM :-+
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Offline Ice-Tea

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Re: What you use benchtop 5.5digit+ DMM for?
« Reply #51 on: August 29, 2016, 08:16:36 pm »
So, if you have to buy another DMM, might as well buy one of the benchtop variety.

Why? Because you can't explain to the missus you need two times the same instrument. A bench DMM looks like something different entirely  :-DD

Ah, well, that depends. If the missus has two or more of anything in different colors, then you can do the same with handheld DMMs. e.g.,

Greenlee = green DMM
Keysight = orange DMM

Different = win! :-DMM :-+

So, you would seek to solve marital strive through logic?  :-DD :popcorn:

Offline bitseeker

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Re: What you use benchtop 5.5digit+ DMM for?
« Reply #52 on: August 29, 2016, 09:42:19 pm »
So, you would seek to solve marital strive through logic?  :-DD :popcorn:

LOL! I should've added, "YMMV".
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Offline rsjsouza

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Re: What you use benchtop 5.5digit+ DMM for?
« Reply #53 on: August 29, 2016, 09:45:02 pm »
I didn't have a use for a bench DMM but I couldn't pass on a Keithley 191 for US$10.00. I then started using it for 4-wire resistance measurements.
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Offline ez24

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Re: What you use benchtop 5.5digit+ DMM for?
« Reply #54 on: August 29, 2016, 10:50:55 pm »
Tin are you going to convert your bad 8.5 meters to good 5.5 meters (is this possible?)
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Offline Macbeth

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Re: What you use benchtop 5.5digit+ DMM for?
« Reply #55 on: August 29, 2016, 11:23:39 pm »
@ez24 - Why do you persist with this bizarre idea TiN has hundreds of 8.5 digit meters?

From what I recall he has 1x 3458A and 1x K2002 (maybe another sick/uncalibrated one). He does have quite a handful of 7.5 digit K2001's too. So it is clear <=6.5 digit stuff is beneath him  :-DD

Why would anyone?... 8.5 digit... convert... 5.5 digit...    |O :-//
 

Offline ez24

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Re: What you use benchtop 5.5digit+ DMM for?
« Reply #56 on: August 30, 2016, 12:08:18 am »
@ez24 - Why do you persist with this bizarre idea TiN has hundreds of 8.5 digit meters?

From what I recall he has 1x 3458A and 1x K2002 (maybe another sick/uncalibrated one). He does have quite a handful of 7.5 digit K2001's too. So it is clear <=6.5 digit stuff is beneath him  :-DD

Why would anyone?... 8.5 digit... convert... 5.5 digit...    |O :-//

I thought he bought a pallet load of them ??   Maybe not 100's but dozens ?
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Offline TiN

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Re: What you use benchtop 5.5digit+ DMM for?
« Reply #57 on: August 30, 2016, 12:12:43 am »
Both my 2xK2002 and 1x3458A are good and happy now after hundreds of man-hours spent on them.  :-/O :-DMM
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Offline Assafl

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Re: What you use benchtop 5.5digit+ DMM for?
« Reply #58 on: November 13, 2016, 09:53:44 am »
Kind of old thread - but I remembered answering it and just encountered a good example of where a 5.5-6.5 digit DMM actually helped quite a bit: measuring RTD PT1000) resistance at a precision of 0.01C.

Measuring value was around 37C which for a PT1000 RTD corresponds to about 1.14k ohm. At that range (the 1k range which goes up to 1.2k) the HP34401A uses a 1mA test current which resulted in about 1.4mW to be dissipated on the PT1000. Self heating caused the temp to drift over 0.1C over time - and losing all pretense of precision! 

Switching manually to the 10K range - the test current drops to 100uA at the range and power dissipated drops to about 14uW - and the RTD temp stopped drifting altogether. But you loose a digit! However, loosing a digit with 6.5 or even 5.5. digits is not an issue as all you really need is about 4 digits to get a useful 0.01C resolution.

Another option would have been to use LabVIEW to initiate a fast measurement periodically (e.g. every minute) and disable the test current between measurements - the availability of extra digits for this test case made this option redundant.
 
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Offline GigaJoe

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Re: What you use benchtop 5.5digit+ DMM for?
« Reply #59 on: November 13, 2016, 05:24:12 pm »
Its a magic of digits, you connect dmm to something and numbers changing, so you sitting relaxed .... drinking coffee (or stronger), watching numbers. Like some love a open flame, or petrol-head smells gasoline ..... radiohead likes numbers , it nothing special.  Then woke up, switch to 3 digits and start to poking around; as 6 digits slow, making garbage, and tend you to zoom out.

One of my schematic was sensitive to moving finger around changing output to +0.6 mV DC. that not suppose to. it appears of self-oscillation, funny thing it kills  when scope was connected, so high resistance DMM can reveal it. that the only case was, when 5.5 helps, and yes set in manual for 30V range you measure literally everything. but i hate not having null diff. in 3478a - that so useful sometimes.


 

Offline JohnG

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Re: What you use benchtop 5.5digit+ DMM for?
« Reply #60 on: November 15, 2016, 07:24:42 pm »
I use an Agilent 34970A in 6.5 digit mode to measure power supply efficiency and loss. Since I deal with power supplies with efficiencies into the upper 90% range, with 96-98% percent relatively common, accurate measurements are a must. The problem arises because as you go higher in the efficiency, the loss becomes a smaller difference of large numbers. Since the size of the power supply is determined in a large part by the loss, it turns out to be pretty important.

I have found 6.5 digits is just enough. The scanning meter eliminates a large source of error by using the same ADC to make all four measurements.

I also have heat sinks and fans on my shunts. They are my main source of error right now. No, I am not crazy...

John
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Offline WackyGerman

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Re: What you use benchtop 5.5digit+ DMM for?
« Reply #61 on: November 15, 2016, 07:35:35 pm »
In my case I use my R&S HMC 8012 for long time power measurements . It is really handy for documentation with screenshots on a PC with the HM Explorer . The 5,5 digit display was not the main reason for purchase this DMM but it is a nice bonus feature
 

Offline Alex Nikitin

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Re: What you use benchtop 5.5digit+ DMM for?
« Reply #62 on: November 16, 2016, 09:27:39 am »
At work I need to measure the stability of various power supplies down to <10 ppm level and stability of RF (mostly about 2 MHz, but occasionally up to 10 MHz) in 100ppm range, to measure and match low and high (up to 1Gohm) resistances accurately, to measure resistance drifts with temperature and time down to 10ppm level, to detect and measure DC offsets and ground potential differences to micro-volt levels. For that reason we have HP3458A, Keithley 2000 and now Keysight 34465A.

At home (on top of my fairly recent volt nuttery) I use my two Keithley 2015 and Solartron 7150 plus for accurate audio measurements, resistance matching and also for accurate AC level measurements at 160 kHz in my alignment cassette tapes making setup. My personal hand held meter is 300000 counts MetraHit 28S  ;) .

Cheers

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Offline mrt6644

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Re: What you use benchtop 5.5digit+ DMM for?
« Reply #63 on: November 17, 2016, 03:18:30 am »
I use my 6.5 digits to make sure my 5.5 digit is in order  :-DD


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