Author Topic: Cropico ESC1 electronic standard cell / a look inside.  (Read 9112 times)

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Offline lowimpedance

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Cropico ESC1 electronic standard cell / a look inside.
« on: March 16, 2016, 05:36:23 am »
Another bit of obsolete 80's vintage volt ref kit. Used as a travelling  transfer standard for labs etc.
This sample is one of, (rescued!), quite a few that were tossed out a number of years back and has sat un used in a dark corner of my junk cupboard till now.
Some pics of the front, the rather large number of battery holders (18 D cells), the inside of the front terminals with some noise filtering. Also a series of pics
of the various covers being removed down to the REF pcb and its copper box holding the zener.
I tried to power it up from a bench supply to get a pic of a 34401 reading the outputs but before I got the camera the unit went  :-BROKE...............lol.
Noted the dipped tants. >    odds on its one of them.
 
The odd multimeter or 2 or 3 or 4...or........can't remember !.
 
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Offline lowimpedance

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Re: Cropico ESC1 electronic standard cell / a look inside.
« Reply #1 on: March 16, 2016, 05:39:00 am »
And to complete the documentation here is the operators handbook, some useful info of its development from Cropico and a marketing flyer.
The odd multimeter or 2 or 3 or 4...or........can't remember !.
 

Offline Richard Head

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Re: Cropico ESC1 electronic standard cell / a look inside.
« Reply #2 on: March 16, 2016, 05:52:21 am »
Looks like a Matryoshka doll. Probably very effective at controlling the temperature.
 

Offline manganin

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Re: Cropico ESC1 electronic standard cell / a look inside.
« Reply #3 on: March 16, 2016, 11:30:23 am »
And to complete the documentation here is the operators handbook

The reference is practically identical to the LTZ1000 circuit (without an op-amp). Including the 120R resistor and the 5mA current.

Looks like a Matryoshka doll. Probably very effective at controlling the temperature.

Looks like a pay day for the die cast enclosure manufacturer.
 

Online Vgkid

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Re: Cropico ESC1 electronic standard cell / a look inside.
« Reply #4 on: March 16, 2016, 01:10:28 pm »
Thanks for the teardown, certainly an interesting unit.
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Offline Andreas

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Re: Cropico ESC1 electronic standard cell / a look inside.
« Reply #5 on: March 16, 2016, 08:00:07 pm »

The reference is practically identical to the LTZ1000 circuit (without an op-amp). Including the 120R resistor and the 5mA current.


And even with the tempco adjustment resistor from the application note of the LTZ1000.
I think LT has learned much from this cirquit.

With best regards

Andreas
 

Offline zlymex

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Re: Cropico ESC1 electronic standard cell / a look inside.
« Reply #6 on: July 21, 2016, 06:47:17 am »
Thanks very much for the teardown and for the documents.

I have a question, why they choose 20 degree C for the peak/flat portion instead of 23 degree C?
Is/was the standard temperature in the UK different than that of US?
 

Online Vgkid

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Re: Cropico ESC1 electronic standard cell / a look inside.
« Reply #7 on: July 21, 2016, 06:56:38 am »
looking through my Solartron 7065 They also used 20C, as opped to my other American meters using 23C.
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Offline Andreas

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Re: Cropico ESC1 electronic standard cell / a look inside.
« Reply #8 on: July 21, 2016, 07:32:26 pm »

 (SZA 263 - Motorola)


Hmm,

what has the Motorola SZA 263 to do with a Fluke 8840 cirquit?
(attached schematic).

With best regards

Andreas
 

Offline Gyro

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Re: Cropico ESC1 electronic standard cell / a look inside.
« Reply #9 on: July 21, 2016, 07:49:48 pm »
I have a question, why they choose 20 degree C for the peak/flat portion instead of 23 degree C?
Is/was the standard temperature in the UK different than that of US?

Yes, traditionally 68'F... 20'C.   23'C is/was a bit warm for comfort (with our climate, before global warming anyway)  :phew:
Chris

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Offline TiN

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Re: Cropico ESC1 electronic standard cell / a look inside.
« Reply #10 on: July 22, 2016, 11:55:48 pm »
Thank you for teardown, interesting unit indeed. That blue PCB substrate look interesting, is it ceramic based? Doesn't look like standard FR4.
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Offline fcb

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Re: Cropico ESC1 electronic standard cell / a look inside.
« Reply #11 on: July 23, 2016, 10:42:00 am »
Hello - the marketing flyer of Cropico is dated 04-1980 and as Linear was founded one year later in 1981 - I see no relationship between the bespoken ideas of Linear Tech people and implementation of Cropico circuit ?

Bob Pease & Bob Widlar most likely knew about the ideas behind this from their period working earlier together at National, but also other people (SZA 263 - Motorola) had already done earlier work ... and of course Paul Brokaw (ADI). Here is an University video that was recorded in 1989 - Paul Brokaw explaining his Bandgap reference for future student classes.

https://archive.org/details/APaulBro1989

Fred
Cropico (Croydon Precision Instrument Company) was formed in the early 50's in England, and was bought by Seaward in recent decades.  They likely had the VREF design working a few years before it was released (as an internal project) and that flyer was dated.
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Offline lowimpedance

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Re: Cropico ESC1 electronic standard cell / a look inside.
« Reply #12 on: July 25, 2016, 11:24:16 pm »
Thank you for teardown, interesting unit indeed. That blue PCB substrate look interesting, is it ceramic based? Doesn't look like standard FR4.
Hmm, When I was taking the pics of that unit I did not get the impression the PCB material was anything special but indeed the color was a surprise. (cant check easily since its all boxed back up)
I have another unit which has a normal looking FR4 PCB in that part.
The odd multimeter or 2 or 3 or 4...or........can't remember !.
 


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