Pragmatic 9001 DC Voltage Reference

[gilbenl]

Pragmatic adj.-Dealing with things sensibly and realistically in a way that is based on practical rather than theoretical considerations.

Got this because I wanted to know what kind of voltage reference a company with the name "Pragmatic" would make. Half the board was under a metal block and figured it was an oven. Nope-REF101, which doesn't have a heater, and an OP27. Does it strike anyone else that a lot of wasted effort went into not much reference?

[Vgkid]

Now ovenize it.

[barnacle2k]

wow, i had that thing on my watchlist considering it.
Yes i too expected more from that thing.

hindsight - always 20/20

[codeboy2k]

Yep, not much there except a buffered 10V reference chip.

They did a lot to try to shield it well, and give the separate circuit areas their own ground returns.  That's good.

I'm a bit surprised to see an LT317 there.  A much lower-noise regulator can be made from better parts.  That said, they didn't even try to reduce the noise on the LM317 as they used it. The simple addition of a 10u bypass cap at the bottom resistor of the divider (R6 in the photos) can dramatically reduce the output noise.

It's interesting how they jumpered the ground connections into the shielded area.  The shield is pulled back and raised jumpers are used. What's the point of the raised jumpers like that; they don't jumper over anything.

what could have been done instead?

(1) at least an LM399 (which needs an opamp to multiply it up, but they already have one there now)
(1a) -- add a TC matched pair of divider resistors for the opamp gain
(2) lower noise, more precise voltage regulator
(3) shielded cable to bring the + and - ports out to the front, since they went to the trouble to guard it like they did, then left open wires flappin' in the breeze to pick up noise.
(4) oven ? maybe if they stick with the REF102, yes.

[gilbenl]

They did a lot to try to shield it well, and give the separate circuit areas their own ground returns.  That's good.

It's interesting how they jumpered the ground connections into the shielded area.  The shield is pulled back and raised jumpers are used. What's the point of the raised jumpers like that; they don't jumper over anything.

Above is why I find the company name "Pragmatic" so comically fitting. You have some great suggestions. I only paid a bit for the thing so I think it may be a good candidate for some hacking. I don't think the REF101 and REF102 have remotely similar pins, but that may be fixable...I'll try to post a schematic if anyones interested.