EEVblog #210 - Krohn-Hite DC Voltage Standard Teardown & Calibration

A Krohn-Hite MV106J DC Voltage Standard calibrator landed on Dave's bench. What's inside? How does it work? Is it still within spec?, and what's all this (lack of) Kelvin-Varley and LM299 zener reference stuff anyhow?
And no adventure in calibration check is complete without a visit to the TrioSmartCal lab.

Category:

Science & Technology

Tags:

• Krohn-Hite
• mv106
• mv106j
• dc
• voltage
• standard
• teardown
• calibrate
• calibration
• lab
• burried
• zener
• diode
• reference
• lm299
• lm199
• lm399
• fluke
• hp
• agilent
• hp3478a
• 3478
• 3478a
• laboratory
• nata
• certification
• schematic
• parametric
• graph
• curve
• temperature
• compensation
• kelvin
• varley
• divider
• datasheet

[MichelDeSarcelles]

The final tempco is not only caused by the Zener tempco but mainly by the resistors. Like all Zener diode there is a specific forward current which causes the tempco to be closed to zero. I guess that each diode is tested in an oven to determine this particular current, and the source current is set to this specific current.

[EEVblog]

@MichelDeSarcelles Yes, they would have individually tested and selected I'm sure. "Close to zero" ain't zero though, so it still matters. You can get special "zero tempco" foil resistors too, once again, close to zero, but not zero :-> The exact parts used in this instrument aren't known though.

[bfestevao]

@EEVblog Hi Dave!!. great video!. I was thinking if it's a good idea do some modification to obtain that temperature compensation, that LM you showed have a heater, is it viable to wrap the MV106J's diode and design a temperature control circuit?.. maybe with galvanic insulation to avoid some problems..

Thanks!

[EEVblog]

@bfestevao Yeah, possible, but you'd have to weigh up how much improvement you'd get. The tempco is already more than low enough for my use at least.

[Gameboygenius]

Why didn't you go all the way out and use sense return in the cal lab? Also, why did you cut out the audio near the end? Dirty talk in this pornographic setting? ;)

[EEVblog]

@Gameboygenius For such a short run, with high input impedance, there is no benefit in 4 wire in this instance.

The silence, I meant to cut out more of that, looks like my edit failed. Charles's phone rung with an important call :->

[slaithen]

I like the teardowns, but as a novice electronics hobbyist, I would love to see more videos focusing on tutorials and design ideas.

Having said that, this video went into more detail of the reasons and considerations put into the design of this source. Very nice explanation of the schematic!

Thanks for all the stuff you do Dave, we love it.

[prayag123456789]

can you do some more tutorials ?

[jacekpaw1]

Dave please take us for the trip to this metrology lab. I'm sure that many peoples (including me) are very curious how does the lab work's.

[schimpl94]

Can you sent me the circuit diagramm of the MV106J ?

That would be great :-)

[daafies2]

Nice find!

[bejius]

17:30 what is the name or brand-name of this transparent plastic insulator ? I've seen it before many many times but I never knew what they are called besides "plastic insulator"

[criscros7]

The whole thing looks DIY, especially the PCB. I've never seen anything like this sold commercially (then again, I haven't seen a lot of gear from the inside). I'm not saying that that's a bad thing, just that it looks as if a hobbyist like myself had done it. Charming. :)

[TrueBlueAustralian]

mmm nice

[besaid00]

Dave, wouldn't the voltage change when you put an actual load on the output?

[thewii552]

Am I the only one that noticed the Bob Pease reference in the description? I like how you put that in. RIP legend Bob Pease

[rapsod1911]

Thank you very much for very informative video. I have watch it 5 times. What a surprise!!! Big box, small board and no vodoo magic.