Cropico ESC1 electronic standard cell / a look inside. - Page 1
Forum section: electronics / general

author: lowimpedance
author_rank: Super Contributor
timestamp: March 16, 2016, 05:36:23 am
content: 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 picsof 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...............lol.Noted the dipped tants. > odds on its one of them.

author: lowimpedance
author_rank: Super Contributor
timestamp: March 16, 2016, 05:39:00 am
content: And to complete the documentation here is the operators handbook, some useful info of its development from Cropico and a marketing flyer.

author: Richard Head
author_rank: Frequent Contributor
timestamp: March 16, 2016, 05:52:21 am
content: Looks like a Matryoshka doll. Probably very effective at controlling the temperature.

author: manganin
author_rank: Regular Contributor
timestamp: March 16, 2016, 11:30:23 am
content: Quote from: lowimpedance on March 16, 2016, 05:39:00 amThe reference is practically identical to the LTZ1000 circuit (without an op-amp). Including the 120R resistor and the 5mA current.Quote from: Richard Head on March 16, 2016, 05:52:21 amLooks like a pay day for the die cast enclosure manufacturer.

author: Vgkid
author_rank: Super Contributor
timestamp: March 16, 2016, 01:10:28 pm
content: Thanks for the teardown, certainly an interesting unit.

author: Andreas
author_rank: Super Contributor
timestamp: March 16, 2016, 08:00:07 pm
content: Quote from: manganin on March 16, 2016, 11:30:23 amAnd even with the tempco adjustment resistor from the application note of the LTZ1000.I think LT has learned much from this cirquit.With best regardsAndreas

author: zlymex
author_rank: Frequent Contributor
timestamp: July 21, 2016, 06:47:17 am
content: 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?

author: Vgkid
author_rank: Super Contributor
timestamp: July 21, 2016, 06:56:38 am
content: looking through my Solartron 7065 They also used 20C, as opped to my other American meters using 23C.

author: Andreas
author_rank: Super Contributor
timestamp: July 21, 2016, 07:32:26 pm
content: Quote from: Flinstone on July 21, 2016, 05:21:28 amHmm,what has the Motorola SZA 263 to do with a Fluke 8840 cirquit?(attached schematic).With best regardsAndreas

author: Gyro
author_rank: Super Contributor
timestamp: July 21, 2016, 07:49:48 pm
content: Quote from: zlymex on July 21, 2016, 06:47:17 amYes, traditionally 68'F... 20'C. 23'C is/was a bit warm for comfort (with our climate, before global warming anyway)

author: TiN
author_rank: Super Contributor
timestamp: July 22, 2016, 11:55:48 pm
content: Thank you for teardown, interesting unit indeed. That blue PCB substrate look interesting, is it ceramic based? Doesn't look like standard FR4.

author: fcb
author_rank: Super Contributor
timestamp: July 23, 2016, 10:42:00 am
content: Quote from: Flinstone on July 21, 2016, 05:21:28 amCropico (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.

author: lowimpedance
author_rank: Super Contributor
timestamp: July 25, 2016, 11:24:16 pm
content: Quote from: TiN on July 22, 2016, 11:55:48 pmHmm, 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.