Schematics on Resistor Simulation by Calibrators

[Echo88]

Calibrators like the Fluke 5500A generate a variable resistance on its output by using a "Synthesized Impedance Assembly". download.flukecal.com/pub/literature/5500a___smeng0600.pdf Page 48

Id like to learn from it and perhaps someone can provide suitable schematics of such an assembly? I havent found anything, but maybe there are old calibrator service manuals which include those schematics.

[lukier]

Interesting. I would like to know more about this as well.

Is it similar to the approach used in Valhalla 2724A? They call it active ohms and it looks very similar (a reference resistor plus a variable gain amplifier).

[CalMachine]

This might be the same information, reiterated... but it might be worth a look.

http://download.flukecal.com/pub/literature/9100_vo1umeng0000.pdf

Sections 4.7.5.3 and 4.7.5.4 have a slightly more detailed graphic.

[lukier]

Thanks CalMachine.

I first became aware of this technique when I encountered Valhalla 2724A mentioned here on the forum and studied the service manual a bit. I always thought resistance calibrators are just a lot of precision resistors and relays, like in Fluke 5450A, but to my surprise the specs of 2724A are almost as good (I guess derived from few quality resistors + LM399), while being much more versatile.

Experimenting with this type of resistance standard is on my TODO list now (that usually means never  ) and I wonder what the limitations are. 2724A goes up to 12 GOhm which is a lot. I guess one cannot use this approach to calibrate things like LCR meters or possibly electrometers (different resistance measurement scheme).

[CalMachine]

Thanks CalMachine.

I first became aware of this technique when I encountered Valhalla 2724A mentioned here on the forum and studied the service manual a bit. I always thought resistance calibrators are just a lot of precision resistors and relays, like in Fluke 5450A, but to my surprise the specs of 2724A are almost as good (I guess derived from few quality resistors + LM399), while being much more versatile.

Experimenting with this type of resistance standard is on my TODO list now (that usually means never  ) and I wonder what the limitations are. 2724A goes up to 12 GOhm which is a lot. I guess one cannot use this approach to calibrate things like LCR meters or possibly electrometers (different resistance measurement scheme).

They can actually be a pain to deal with sometimes.  With the 9100, as it was designed to calibrate handheld multimeters.  In my experience, when you go to try and measure resistance via 4 wire measuring device, like a 3458A, they often don't cooperate with each other.  A 5500 or 5520 work flawlessly with a 3458A. 

You are also correct, that cannot use this type of resistance source to calibrate certain types of equipment.   For instance, a Megaohmeter or Electrometer.

[Echo88]

Sadly there are no schematics/service manuals available for both Wavetek 9100 and Valhalla 2724A, although the Wavetek graphic makes the practical approach a bit clearer.

[lukier]

Sadly there are no schematics/service manuals available for both Wavetek 9100 and Valhalla 2724A, although the Wavetek graphic makes the practical approach a bit clearer.

Artek sells the 2724A service manual for IMHO a reasonable amount:
http://www.ebay.co.uk/itm/390595429766
http://artekmanuals.com/manuals/other-manuals/

[TiN]

However there is schematics of Fluke 57LFC, which is essentially 5522Amix of 552x and 57xx in system only rack chassis.    No resistance synth in this one though.

[Echo88]

Indeed a reasonable amount. But i searched a bit more and found it: http://www.lost-manuals.com/equipment.php?id=15380    Also just uploaded it to http://www.ko4bb.com. Since youre also watching TiN: This would also be useful in the xdevs archive?

Well, time to study. 

Edit: Seems the first page of the schematic is missing. So it doesnt tell the whole story.
Edit2: Found the missing first page. Now its complete. 

[Echo88]

The Fluke 57, just like the 5200A, is not capable of producing a programmable resistance, it can only output its built-in-standard resistor values.

[fcb]

However there is schematics of Fluke 57LFC, which is essentially 5522Amix of 552x and 57xx in system only rack chassis.    No resistance synth in this one though.

That is a shocking level of detail & schematics to!  Surprising especially since they are dated 2004. Book marked.

[Mickle T.]

Fluke patents

[martinr33]

Quote from: TiN on Yesterday at 07:59:05 PM
However there is schematics of Fluke 57LFC, which is essentially 5522Amix of 552x and 57xx in system only rack chassis.    No resistance synth in this one though.

and from fcb:
That is a shocking level of detail & schematics to!  Surprising especially since they are dated 2004. Book marked.


That manual is for the Navy and its contractors, same idea as that Fluke 2001 manual that appeared. The US military probably has these manuals for everything we see. That means they will eventually slip out.   

[Mickle T.]

Simplified Valhalla schematics (with software MDAC) working is very well.

[Echo88]

Youre ahead of us as always i see. 

[lukier]

Simplified Valhalla schematics (with software MDAC) working is very well.

Every time some metrology idea comes up it turns out Mickle T. already did it Chapeau bas!

[ManateeMafia]

Simplified Valhalla schematics (with software MDAC) working is very well.

Every time some metrology idea comes up it turns out Mickle T. already did it Chapeau bas!

I am patiently waiting for Mickle T. to show us his homebrew JJA.

[carl_lab]

Has anybody realized an inductor simulation (virtual inductor) for calibration purpose?
http://downloads.hindawi.com/journals/apec/1989/039762.pdf

[lukier]

Simplified Valhalla schematics (with software MDAC) working is very well.

I have few questions about this circuit. I hope you don't mind.

If I guess the operation correctly, you route one of the leads from the DMM to the X3-VIN input, while being grounded via the reference resistor (jumper wire on the photos), that voltage drop across the reference resistor gets amplified by U22:A and resistors via DG413 and goes to AIN0 of the ADC. Now purely in software, no analog loops, you read that from the ADC and program the DAC accordingly to drive the X5-VOUT that goes to the second lead from the DMM, thus generating voltage across the DMM leads that the DMM converts into the resistance. The VSENSE from the DAC is fed into the ADC for the digital feedback loop.

I suppose that in 4W mode you just connect negative force and sense to the negative binding posts, no special care required.

1) what are the resistor networks R10, R21 (M3NRE001S-VERT) and R24 (DIVSTAT-10-100) - couldn't find anything on those. R24 resembles something like CADDOCK 1776?
2) it is described as Hamon, but where is the Hamon autocal action, that is series-parallel rewiring the upper leg of the divider?
3) what is the purpose of ZSENSE ADC input?
4) how good is your autocal? I see feeding the raw LM399 voltage into the ADC input front end to adjust for that, but is this going to take care of the reference scaling done by R10 and R24 (thus DAC calibration as well)?

Thanks!

[hwj-d]

Simplified Valhalla schematics (with software MDAC) working is very well.

...
1) what are the resistor networks R10, R21 (M3NRE001S-VERT) and R24 (DIVSTAT-10-100) - couldn't find anything on those. R24 resembles something like CADDOCK 1776?
2) it is described as Hamon, but where is the Hamon autocal action, that is series-parallel rewiring the upper leg of the divider?
3) what is the purpose of ZSENSE ADC input?
4) how good is your autocal? I see feeding the raw LM399 voltage into the ADC input front end to adjust for that, but is this going to take care of the reference scaling done by R10 and R24 (thus DAC calibration as well)?

Thanks!

Thats my questions too.
Maybe, these are the resistors and black boxes in the left down corner:
https://www.eevblog.com/forum/metrology/lm399-based-10-v-reference/msg1110430/#msg1110430
Seems to be some russian gear? 

[Mickle T.]

1) M3NRE001S (black boxes) - metrological level custom BMF divider. Used in the standard laboratories DC voltage references.
R24 (DIVSTAT-10-100) - DIY Hamon type divider without autocal action (20 pcs hermetic BMF resistors on the subboard).
3) ZSENSE is used for LO-to-LO current path voltage difference measurement.
4) Currently a LM399 voltage isn't used in autocal procedure.

[LaserEng]

Sorry to resurrect an old thread but I have the service manual with schematics of Fluke 5500A, including impedance synthesizer schematics.

The full service manual is too big to attach to the post, it can be downloaded from the dropox link below for your reading pleasure   

https://www.dropbox.com/s/48p5qlqob1f4ysj/FLUKE%205500A%20SERVICE%20MANUAL%20WITH%20SCHEMATICS.pdf?dl=0

[chekhov]

Thanks LaserEng,

Maybe it is possible to upload this to ko4bb.com which seems to be the right place to share this precious thing ?

[LaserEng]

Thanks for the link, manual now uploaded to ko4bb.

[bfsy]

Thank you for sharing the 5500A schematics.
FLUKE 5520A Error 1504 when trying to output 100kohms 10kohms 1kohms ...
But no error when output 1Mohm 10Mohm ...
Who has the 5520A schematics