ECN Forum Forums Technical Discussion Electrical Theory and Applications Signal Conversion

RSmike, I D/L'd several data sheets from the site that you mentioned. I wouldn't hesitate to use them if I had a control cabinet with DIN rail mounted components and a suitable PS. I appreciate that you posted them.

I emailed a couple of active and passive solutions to Robert and to Scott for posting I would be happy to fwd to you if you Email me, so we can all be on the same page.

Robert's needs seem to be more of factory bench testing with up to 8 changing inputs. I envision a panel with 8, linear pots. I would probably also use 8, NO PBs feeding a common wire to a DPM, so you can read the voltage on any wiper duing setting. The pots would all be fed from 0 and +10V. The V-Vs would feed Op Amp followers and the V-mAs would require the precision 625 ohm resistors going to a precision -2.5 volt reference.

The lab/basement is nice to have. That's where all the parts live. I transfer, etch, tin plate, drill, screen, spray, bake, stuff, and test the PCBs there. But the basement only has a dehumidifier so I layout and output to toner transfer paper from the office with the A/C.

How many times have you found a supplier who makes "almost" what you need? By the time you go through the hoops to make it "exactly" what you need, sometimes it's easier to build it.
Joe

Every time!

By the way, there are four ways to get 625 ohms using standard EIA-96 (1% or better) values in series:

475+150, 523+102, 324+301, and 316+309.

Also, 16.9K in parallel with 649 gets you pretty close.

(I got tired of doing this stuff by hand a long time ago, and wrote some utility programs to find the best series, parallel, and ratio values.)

If you are handy with a soldering iron, you could build your own V/I converter using a chip like the XTR110 from Burr-Brown: http://kolter.de/xtr110.pdf

Because you need to source 4 mA of current with zero voltage input, you will NEVER get there with a purely passive network of resistors.

[This message has been edited by NJwirenut (edited 08-20-2006).]