Good day to all. We've just been contacted and asked if we can design an inexpensive=20 current source that is computer controlled. However, the specs are=20 considerably higher than anything that I've done in the past. What they want: Output current adjustable from 10uA to 1 Amp. Step decade ranges are=20 acceptable - it does not need to be able to be adjustable over a 5=20 decade range in one fell swoop. Output voltage compliance of !! -5V !! to +10V. I don't know if they=20 really want this thing to be capable of a bipolar output but am in=20 the process of finding out. For now, assume that the output=20 compliance is single polarity only. Here's the kicker: accuracy of 0.01% of the set-point. I don't yet have any idea of frequency response requirements but,=20 again, am in the process of finding out. However, I *think* that=20 they are doing battery coulometry, so slow response is probably acceptable. The customer wants the units to be computer controlled. I was just=20 going to use some form of USB - Serial arrangement - most likely=20 using USB-equipped PICs. I do plan to isolate the unit from the host=20 USB port with some form of isolation barrier. I do adjustable current sources and sinks with 8 to 10 bit accuracy=20 on an irregular basis. But this is the first time that I've been=20 asked to do something approaching 14 bits of accuracy. Questions: Is anyone aware of something with similar specs that is already=20 readily available? The customer is currently using a bunch of=20 expensive Keithley units and is looking for less expensive=20 alternatives. Personally, I'd rather point the customer to an=20 already-existing solution rather than starting this particular design cycle= .. But: if I do have to design this beast, Does anyone have any favorite=20 A/D and D/A convertors that are 14 bit accurate or better? I don't=20 normally use parts that accurate and would prefer to have people whom=20 I trust make suggestions rather than just starting to pour over=20 data-books and find out that the parts that at first seem to make=20 sense are now unobtainium. SPI preferred, I think, but willing to=20 look at anything. Many thanks! dwayne --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .