Current source

You have recently proclaimed yourself to be a "master circuit designer", so show us a circuit.

John

Reeds are ok although I've had the ocassional one go "plink" inside the glass tube. RF relays can develop contact issues over time. Those relays do not like small signal stuff, just like a car engine they need the occasional power ride with gusto.

Use the mercury-wetted ones... if Obama still allows them :-) ...Jim Thompson

yes, its called wetting the contacts. One could advance the circuit to place a load on the contacts when not in use with a time circuit.

Jamie

Reeds are big, expensive and, in my experience, not very reliable.

We've used thousands of the little Fujitsu DPDT surface-mount telecom type relays, both regular and latching, and they are great.

John

Well, if you can get them with gold plated contacts, then thsy can be used in "dry" circuits..

Did you start using google groups? I can't see your new posts.

No, nothing new. I use Supernews and Agent.

Can you see this one?

John

Could you repeat that?

nuq ta'ta' SoH jatlh ?

I can't see that one either. I'm testing nfilter settings now to find what's doing it. But that hasn't changed here either, and I see his posts from 3 days ago.

That line is a little too mysterious, where there's a capital S with only one blank space before it. Not enough room for a period and a space.

Oooooh.....I hope you post that schematic.

Shows up fine here, for one data point. No superfluous spacing or other artifacts.

Unlikely to be anything that sexy--I have a bunch of physicist-style resistors in the drawer. Probably just some banana jacks, three pots for voltage ramp begin, end, and slope, and a couple of TIAs with 10Mish feedback resistors and a pot each to set the noninverting input voltage. The simple way to build that would require one one quad CMOS op amp e.g. a LMC660C, because I have pots of them, and a BAV199 across each one's input terminals to protect it. Readout will be on an analog scope (Tek 475A).

I might put the feedback resistors on dual banana plugs for convenience. I just got a bag of 500 banana jacks for $11 on eBay, so the possibilities are limitless. ;) They're all this repulsive shade of mauve, but that's what Sharpies are for.

It'll be dead bug style in a die-cast aluminum Bud box, because I like them a lot--no EMI worries, bulletproof, easy to drill, and reasonably cheap. Of course I have to test the banana jacks for leakage--hopefully the housings are something nice like PET and not PVC or (ugh) nylon. Otherwise I'll have to use a plastic box.

If I decide that I need it to work at higher voltage, it might get a bit more difficult.

Cheers

Phil Hobbs