Agilent E3631A Specifications - help what the spec sheet actually means?

[gerrysweeney]

Have a look at the programming accuracy specs on the data sheet

http://cp.literature.agilent.com/litweb/pdf/5990-4573EN.pdf

Any idea how to interpret the programming accuracy when its expressed as 0.05%+20mV ?

these are the specs I am trying to understand but I have no idea how to interpret what they actually mean.  On the face of it the accuracy is not that great if I am reading it right.  A 5v, 0.05% is about 25mV so that plus 20mV would suggest the programmed voltage output would be somewhere within 50mV of the programmed voltage.  at the other extreme, it I set 100mV then 0.05% of that is only 500uV + 20mV which at this end would suggest the programmed output should be within 20% of the programmed ouput.

Am I reading those specs correctly? Can anyone offer any insight?

Interestingly enough the PSU design actually uses an Audio DAC which at least two people advised me was actually not a good idea (http://www.analog.com/static/imported-files/data_sheets/AD1851_1861.pdf) for a programmable PSU - go figure...


Thanks

[Bored@Work]

You have the right idea, but screwed up your math <insert obligatory rant about today's youth here>.

5 V * 0.05% = 2.5 mV


Edit: Regarding the DAC, if you check the datasheet you see a severe lack of information for non-audio applications. This is one of the reasons that makes using such a DAC hard in non-audio applications. Can you, at first glance, figure out if that DAC works down to 0 Hz, aka DC? And what do you do with the bipolar output? Adding an offset? That requires yet another good reference voltage. Or do you know how the DAC behaves during its 1 min warmup period?

HP certainly knows more about that DAC then we know. Maybe Analog told them, or they measured it. Will Analog tell you, too, or do you want to run some test series to figure out the DAC? of course, if you like that DAC, go ahead, get a few, start measuring and designing.

[gerrysweeney]

Thanks for the response bored@work, sorry I did not reply previously, I only just realised there was a response, I must have missed the mail notification - apologies if I appeared rude.  You must be seriously old if you think I am todays youth....

You are right, I dropped a decimal place....  Re the DAC, I see your point, its very clearly speced for audio yet HP decided to use it so I guess they done the measurements. Its clear though that it works down to DC, although because they mux the DAC output into some sample and hold circuits its never at a steady DC state, its output is around a few Hz - perhaps thats part of the scheme that allows an audio class DAC to work.

Gerry