View Single Post
Old 25th Jan 2019, 10:40 pm   #17
WME_bill
Octode
 
Join Date: Oct 2007
Location: Exeter, Devon, UK.
Posts: 1,553
Default Re: Comark Early 1905 Insulation Meter Checks

Comark. 1905 and1600 series.
As well as posting the 1905 Insulation manual for this forum originally, you will be pleased to know I also have details about the 1600 series of thermometers.
They all use a clever simple design of chopper DC amplifier. The manual is very much a mix and match of the different parts. DC input chopper, temperature compensation, networks for the different types of thermocouple. Meter appears to be 500ua.
Thanks to Bazz4CQJ for his history. My notes say the unit was 1970 - 1971. By 1976, the firm had moved from Rustington Sussex to Welwyn Garden City. My di-azo circuit for the Op-Amp version is dated 1981, so they still have been going then.
The thermometer unit I find very useful. My wife borrows it under careful supervision for marmelade boiling as well.
wme_bill
WME_bill is offline