Ian Johnston PDVS2

[IanJ]

Thinking about this......I think I'll design a separate device, a Precision Digital Current Source.......fully featured from uA to 100mA and include full 4-20mA source/sink functionality.

Ian.

[Vgkid]

You can always implement it as an add on module/unit.

[IanJ]

Hi all,

Couldn't resist testing out the 0 to 2mA source circuit.
I'm using my own PVDS2 to drive the V to I conversion circuit on the breadboard and with the 34461A displaying the output.
10V on PDVS2 converts to 1mA for the purposes of this test.
I also hooked up Dave's uCurrent (1mV/uA) for kicks also and am measuring it's output on my cheap VA38 (questionable cal!).

For a breadboard precision circuit it's quite stable, +/- 0.2uA

Ian.

[ap]

As you work on the new one and as you do an upgrade on the existing one you may wish to have a look at the spec data. Some information might be described a little clearer.
E.g., 0.001% accuracy: this is ususally split into offset and gain and also there is an aging attached to it (not yet established, understand, but...). You will probably not specify 0.001% absolute accuracy (10ppm) of output at any voltage and after say e.g. 10 months. my guess is your voltage standard inaccuracy is maybe already half of it, so not that much left over by the device itself.
Temperature range... I would think, actually, CE had demanded a temp range definition anyhow, so maybe just a miss in transferring this into the manual.
Will help you avoid to not meet expectations you never wanted to meet anyway. And facilitates its use.

[alex-sh]

Hi Ian,

I wonder if you did manage to finish implementing current source into your PDVS2???

Thanks
Alex

[IanJ]

Hi Ian,

I wonder if you did manage to finish implementing current source into your PDVS2???

Thanks
Alex

I did modify one of my PDVS2's to include a 0-2mA current output (keeping the 2v/10v modes), 4 DP's and it works pretty good and can drive a good range of loads. Ever so slightly noisy on that last digit but that's just my prototyping.

No plans to take this into production though, I'd prefer 0-20mA or something like that to make it worth the extra cost...….but it was a fine test.

Pic attached is my one and only prototype........connected up to some cheap arse DMM I just bought and was testing.....

Ian.

[EEVblog]

Pic attached is my one and only prototype........connected up to some cheap arse DMM I just bought and was testing.....

That meter looks dodgy-as!

[EEVblog]

No plans to take this into production though, I'd prefer 0-20mA or something like that to make it worth the extra cost...….but it was a fine test.

I think it would at least need to cover the two shunt ranges, mA and uA.
So maybe 0-200uA and 0-20mA to make it really worthwhile?

[alex-sh]

Where did you get that multimeter? I bet eBay is selling thousands of those

Pic attached is my one and only prototype........connected up to some cheap arse DMM I just bought and was testing.....

Ian.

[alex-sh]

No plans to take this into production though, I'd prefer 0-20mA or something like that to make it worth the extra cost...….but it was a fine test.

I think it would at least need to cover the two shunt ranges, mA and uA.
So maybe 0-200uA and 0-20mA to make it really worthwhile?

I think Dave has got a point here. Personally, I'd be more interested in 0-200uA, but this would have to have to upper scale too

[IanJ]

Where did you get that multimeter?

Found it in a dumpster (as mr. Jones would say).......ahem!

Ian.

[hwj-d]

Pic attached is my one and only prototype........connected up to some cheap arse DMM I just bought and was testing.....

That meter looks dodgy-as!

Hmm, with my poor aussi-inglish, for the very first moment i had read "doggy-ass" ... 

[alex-sh]

Ian,

I just wonder if you do not see a market for such devices or what's the reason you put development on hold?

Thanks
Alex

[niner_007]

Hello

all LM399 are sensitive to orientation (some more and some less).

Hi, would it make sense to use silastic to keep the LM399 plastic enclosure from moving (and on the PCB)?

[2N3055]

Hello

all LM399 are sensitive to orientation (some more and some less).

Hi, would it make sense to use silastic to keep the LM399 plastic enclosure from moving (and on the PCB)?

Andreas didn't mean that LM399 is sensitive to vibration or pin or case stress.
In testing it was shown that if you take whole device that has LM399 inside (like multi-meter or reference) and put on one side, on the other side or upside down, in each stationary position it will give a slightly different output voltage, on PPM level order of magnitude of difference.
It probably has to do with slight difference in thermal flow of LM399 in different orientation......
Metallic case of LM399 is not sensitive to device pin stress...