15-10-2016, 03:05 PM
I have a manual covering a variety of Comark 1600 series analogue thermometers.
They all use DC chopper amplifier, on board 1600/2, input to 30mV to output to 1V driving a 500ua meter, which is packed in together with various range and thermocouple stabilised power supplies depending upon the ranges required.
I wonder if that is also used in the multimeter, and would ber useful to you. It uses 9 BC183 transistors and 3 small diodes 1S920.
I also have the Insulation Tester 1905, (dated 1971) currently waiting for a roundtuit spare part. Range of test voltages, 25V to 1kV. Uses a transistor oscillator, driving voltage doubling/trebling rectifier. Measured with a 10ua meter. The manual also has a circuit for a later version (dated 1980) which uses a couple of Op.Amps and drives a 500ua meter. I got this from them in 1996, when they were at Welwyn Garden City since around 1991, having left the previous address at Littlehampton, Sussex around 1980. So perhaps you can work out who took bought and sold the business from these dates.
wme_bill
They all use DC chopper amplifier, on board 1600/2, input to 30mV to output to 1V driving a 500ua meter, which is packed in together with various range and thermocouple stabilised power supplies depending upon the ranges required.
I wonder if that is also used in the multimeter, and would ber useful to you. It uses 9 BC183 transistors and 3 small diodes 1S920.
I also have the Insulation Tester 1905, (dated 1971) currently waiting for a roundtuit spare part. Range of test voltages, 25V to 1kV. Uses a transistor oscillator, driving voltage doubling/trebling rectifier. Measured with a 10ua meter. The manual also has a circuit for a later version (dated 1980) which uses a couple of Op.Amps and drives a 500ua meter. I got this from them in 1996, when they were at Welwyn Garden City since around 1991, having left the previous address at Littlehampton, Sussex around 1980. So perhaps you can work out who took bought and sold the business from these dates.
wme_bill
