[Boatanchors] DC Voltmeter Calibration

Tue Jan 19 14:26:14 EST 2016

There are a thousand little modules on ebay built around the analog devices AD584 voltage reference

http://www.analog.com/media/en/technical-documentation/data-sheets/AD584.pdf

search ebay for them.  These can be excellent references for your lab.
Eugene

-----Original Message-----
From: Boatanchors [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Jacques Fortin
Sent: Tuesday, January 19, 2016 2:19 PM
To: 'David C. Hallam'; 'Al Klase'; boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] DC Voltmeter Calibration

Hi David,

My 2 cents is: reading 1.651V from fresh Alkaline cells is very much plausible and this not indicates any DMM calibration problem.
I read 1.62 - 1.65 V from a couple of Duracell Quantums with my trusty HP34401A DMM here (.01% accuracy, minimum).

Jacques
VE2JFE

-----Original Message-----
From: Boatanchors [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of David C. Hallam
Sent: Tuesday, January 19, 2016 1:52 PM
To: Al Klase; boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] DC Voltmeter Calibration

I have reached the point where I don't believe my Metex DMM ME11 comes even close to an accurate voltage reading band-gap reference or not.  I tested several fresh AA alkaline cells and they all read 1.651V.  I don't trust its readings any further than I can throw my 2KW amp power supply.

David
KW4DH

On 1/7/2016 3:36 PM, Al Klase wrote:
> CORRECT ANSWER!!!
>
> Modern DVM's all contain band-gap references. These are semiconductor 
> devices that use quantum-physical principles to generate a know 
> voltage. They are much more accurate than anything else you're going 
> to lay mortal hands upon. Sit down with a AA cell, and compare two or 
> three DVM's. You'll be amazed.
>
> In my case:
>
> $300+ Fluke 87 1.588V
> $70'ish Escort 1.589V
> $11 Ebay cheapie 1.592V
>
> A VR tube or Zener diode won't even come close.
>
> Al
>
> Al Klase - N3FRQ
> Jersey City, NJ
> http://www.skywaves.ar88.net/
>
> On 1/7/2016 1:38 PM, D C _Mac_ Macdonald wrote:
>> I'd bet you'd get a lot closer than what you have already by using a 
>> cheap (sometimes even free) digital meter from Harbor Freight as a 
>> "standard for comparison."
>>   * * * * * * * * * * *
>> * 73 - Mac, K2GKK/5 *
>> * (Since 30 Nov 53) *
>> * Oklahoma City, OK *
>> * USAF, Ret'd 61-81 *
>> ** FAA, Ret'd 94-10 *
>> * * * * * * * * * * *
>>
>>
>>> Date: Thu, 7 Jan 2016 13:02:11 -0500
>>> To: boatanchors at mailman.qth.net
>>> Subject: Re: [Boatanchors] DC Voltmeter Calibration
>>> From: boatanchors at mailman.qth.net
>>>
>>> A quick and dirty way that will get you a lot closer than +/- 45 VDC 
>>> would be to rig up a VR-150 running at about 20 mA.
>>>
>>> In a message dated 01/07/2016 10:25:07 AM Central Standard Time, 
>>> dhallam at knology.net writes:
>>>> I obviously need to calibrate my DC voltmeters.  I was setting the 
>>>> 300 VDC B+ on my signal generation after some repairs.  I used 3 
>>>> voltmeters and got a spread of 45V among the 3 of them, low 285V 
>>>> and high330V.  The low was a VTVM and the high  DVM.  What is a 
>>>> good standard to use that won't break the bank to acquire?  I used 
>>>> to have some mercury batteries but they are a no, no any more.
>>>>
>>>> David
>>>> KW4DH
>>> Robert & Susan Downs - Houston
>>> wa5cab dot com (Web Store)
>>> MVPA 9480
>>
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> --
> There are two possible outcomes: if the result confirms the 
> hypothesis,
then you've made a measurement.
> If the result is contrary to the hypothesis, then you've made a discovery.
> Enrico Fermi
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