[volt-nuts] Homebrew DVM

Stan Katz stan.katz.hk at gmail.com
Wed Nov 16 21:48:15 UTC 2011


Hi Andreas,

I own no VRE305A references. However, if you take a look at a co-marketing
article between TI and Thaler in the Nov. 1999 TI Applications Journal, the
typical noise spec for the VRE3050 back then was listed as 3uv between
.1-10hz, just as good as the VRE305A  references Tipton used. However, when
one looks at the noise specs in the datasheets for VRE3050 on the current
Cirrus site, and at the original Thaler datasheets for VRE305/VRE3050 the
maximum/minimum noise specs bounding the 3uv typical are unspecified. I
find this unusual for such a pricey unit.

Stan

On Wed, Nov 16, 2011 at 3:10 AM, Andreas Jahn <Andreas_-_Jahn at t-online.de>wrote:

> Hello Stan,
>
> thanks for the article
> he shows some of the key issues with precision A/D converters.
> Although with the noise he mixes Vpp with rms values.
>
> On the other side I have bougth recently two VRE3050A-References from
> Cirrus.
> (speced nearly the same than VRE305A but only usable with lower minimum
> power supply voltage)
> For the 3uVpp noise I found something around 9uVpp. (0.1-10 Hz)
> Whereas on a LT1027C I measure around 1.9uVpp with the same
> filter-amplifier.
> And even with temperature hysteresis the VRE3050A that I have measured
> is much worse than a LT1027 in a 10-40 degree (Celsius) range.
>
> So I would be interested if the VRE305A is much better than the VRE3050A
> or if the specs have
> changed when renaming the references from Thaler to Cirrus.
> Do you have any measurement values of some recently bought Cirrus VRE305?
>
> With best regards
>
> Andreas
>
> ----- Original Message ----- From: "Stan Katz" <stan.katz.hk at gmail.com>
> To: <pa4tim at gmail.com>; "Discussion of precise voltage measurement" <
> volt-nuts at febo.com>
> Sent: Wednesday, November 16, 2011 2:47 AM
>
> Subject: Re: [volt-nuts] Homebrew DVM
>
>
>  I would think that Ron Tipton's 6 1/2 digit diy DVM, based on LTC2400 and
>> a
>> statistical pool of Thaler(now Cirrus) VRE305A's would be the baseline
>> design to beat in this thread's quest for excellence. Yes?
>> www.tdl-tech.com/hires-vm.pdf
>>
>> Stan
>>
>> On Tue, Nov 15, 2011 at 7:20 PM, Fred <pa4tim at gmail.com> wrote:
>>
>>  The ADC I am gonna use is the LTC2400. A friend who is a digit-nut made
>>> the pcb and will make the software for me.
>>>
>>> About the dual slope experiment. I could look better as it is. The
>>> arduino died before I could do more tests but first results amazed me.
>>> Remember it was just breadboard, no Vref (just resistive divider from
>>> Vcc and, I do not dare to say, but the measurement pictures were taken
>>> after I blew up my last 4066, so I used optocouplers to switch and
>>> strange enough that went very well.
>>>
>>> The drift you see in the measurements is more because the powersupply I
>>> measured the voltage from, is not realy stable. Noise I do not know.
>>>
>>> The experiment was after a discussion on a Dutch forum. There was some
>>> talk about multimeters and ADCs and the a member who works at ST as an
>>> EE told the top meters used dual slope about how easy it is to make a
>>> dual slope ADC. He told us to just try it on a breadboard and gave some
>>> tips. A few of us including me started experimenting with it and I was
>>> trilled it was so easy to get it working like it did. Was fun too. I'm
>>> now reading a lot of literature and your interesting discussions to
>>> learn more before I build my meter using the LTC2400. So thanks for all
>>> the valuable information. As a beginner I    appreciateitverymuch.
>>>
>>> Fred PA4TIM
>>>
>>>
>>> Andreas Jahn schreef op di 15-11-2011 om 23:19 [+0100]:
>>> > Hello Fred,
>>> >
>>> > I asked for the 26 bit (24 bit usable) ADC.
>>> > Do you really get this (noiseless) resolution with a simple dual slope
>>> ADC?
>>> >
>>> > With best regards
>>> >
>>> > Andreas
>>> >
>>> > >
>>> > > http://www.pa4tim.nl/?p=2482 there you see the schematic and some
>>> pictures
>>> > > ( the top one is from the circuit that, i was told, turned out to be
>>> > > a
>>> VF
>>> > > converter)
>>> > >
>>> > > Fred PA4TIM
>>> > >
>>> > >> I am looking now for a converter with less noise.
>>> > >> So what ADC are You using?
>>> > >>
>>> > >>>
>>> > >>> Now I have a 26 bit ( 24 bit usable) ADC waiting to be used
>>> interfaced
>>> > >>> to the arduino, I am making/experimenting with some Vrefs and have
>>> parts
>>> > >>> for a compound chopper based on a LT1052. But the realisation will
>>> be up
>>> > >>> in the future, first gathering more knowledge about percision and
>>> micro
>>> > >>> volt techniques.
>>> > >>>
>>> > >>> Fred PA4TIM
>>> >
>>> >
>>> >
>>> > ______________________________**_________________
>>> > volt-nuts mailing list -- volt-nuts at febo.com
>>> > To unsubscribe, go to
>>> https://www.febo.com/cgi-bin/**mailman/listinfo/volt-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts>
>>> > and follow the instructions there.
>>>
>>>
>>>
>>> ______________________________**_________________
>>> volt-nuts mailing list -- volt-nuts at febo.com
>>> To unsubscribe, go to
>>> https://www.febo.com/cgi-bin/**mailman/listinfo/volt-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts>
>>> and follow the instructions there.
>>>
>>>  ______________________________**_________________
>> volt-nuts mailing list -- volt-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/**
>> mailman/listinfo/volt-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts>
>> and follow the instructions there.
>>
>
>
> ______________________________**_________________
> volt-nuts mailing list -- volt-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/**
> mailman/listinfo/volt-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts>
> and follow the instructions there.
>


More information about the volt-nuts mailing list