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General => Buy/Sell/Wanted => Topic started by: dexters_lab on February 18, 2019, 03:09:12 am

Title: [FS World] Thurlby 1905A 5 1/2 Digit Bench DMM [SOLD]
Post by: dexters_lab on February 18, 2019, 03:09:12 am
This DMM i have had knocking around the lab for a while unused so i am offering it for sale

It's a 1980s vintage Thurlby 1905A bench DMM with 5 & 1/2 digit resolution (also is 6 & 1/2 digit in some ranges), also has several math functions. I have done some basic checks and it all seems to be working. Though i have not checked the calibration. There is plenty of documentation for this meter online, user guides, service manuals etc.

General condition externally is good, there are some marks on the case all just cosmetic. Internally it's very clean, the only issue is two of the internal pegs that hold the case together have broken off inside because the plastic has aged a bit so is only secured by the two front screws, the case doesn't come apart at all so not really an issue, it's just something i thought i should mention.

Some time ago i did swap the original probe sockets for the fully shrouded type as used on modern meters.

Mains input is fixed at 240v.

Looking for £45 + postage from the UK
Postage to UK would be £10. I can post worldwide usually with very good rates.
Title: Re: [FS World] Thurlby 1905A 5 1/2 Digit Bench DMM
Post by: coromonadalix on February 18, 2019, 04:22:11 am
Does it have the true rms converter module in it ?

And the broken stand off, are they still inside stuck to the screws ??


Infos : manuals, schematics

TTi 1905a Multimeter Service Manual (OCR).pdf
http://www.eevblog.com/forum/testgear/thurlby-1905-any-good/?action=dlattach;attach=96220 (http://www.eevblog.com/forum/testgear/thurlby-1905-any-good/?action=dlattach;attach=96220)

TTi 1905a Operating Manual (OCR).pdf
http://www.eevblog.com/forum/testgear/thurlby-1905-any-good/?action=dlattach;attach=96221 (http://www.eevblog.com/forum/testgear/thurlby-1905-any-good/?action=dlattach;attach=96221)
Title: Re: [FS World] Thurlby 1905A 5 1/2 Digit Bench DMM
Post by: dexters_lab on February 18, 2019, 04:59:35 am
Does it have the true rms converter module in it ?

no sorry

Quote
And the broken stand off, are they still inside stuck to the screws ??

yes, they are included inside in a small ziplock bag
Title: Re: [FS World] Thurlby 1905A 5 1/2 Digit Bench DMM
Post by: GreyWoolfe on February 18, 2019, 07:26:43 am
Some time ago i did swap the original probe sockets for the fully shrouded type as used on modern meters.

Not knowing Thurlby equipment, I wouldn't have known you did the swap.  Looks perfect.  I just did the same to my 2 HP 3466 meters.
Title: Re: [FS World] Thurlby 1905A 5 1/2 Digit Bench DMM
Post by: dexters_lab on February 21, 2019, 08:22:33 pm
now listed on ebay:

https://www.ebay.co.uk/itm/303070132866 (https://www.ebay.co.uk/itm/303070132866)
Title: Re: [FS World] Thurlby 1905A 5 1/2 Digit Bench DMM
Post by: macboy on February 23, 2019, 12:57:27 am
This is a nice little meter. My first bench meter was a 1905A. Two curiosities:
- The voltage reference uses the oddball LM3999 [sic].
- An undocumented internal pin header has a 2400 baud TTL UART signal outputting an ASCII version of the display. A USB-UART adapter plus an optocoupler for isolation allows you to log data to PC, or you can capture it with a microcontroller for other processing.

The math capabilities are nice to have. It does Ax+b (good for displaying current through a shunt), dB, logging with Average/min/max display, and rather advanced averaging/filtering. Downsides are the trimpot calibration and manual ranging. Still, it's a good meter and it deserves a worthy home.