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Azur Electronics

COMARK 6130
MICROPROCESSOR THERMOMETER
I bought this unit on eBay with the intention of measuring various temperatures around a heating system in a new house. The 6130 was built in 1981 by Comark Electronics in the UK. So far I have not been able to locate a Manual.

Front view
The switch selects 1 of 10 inputs and the display provides a reading in °C to 1 decimal place. The "u" indicates that no temperature sensor is connected.

Rear view
10 sockets are available for connecting temperature sensors. These are for Type T thermocouples with a range of -200°C to +400°C. There is a data output jack socket ±1V FS (full scale) with a switch to select x1, ÷5 or ÷10.

Top view with cover removed
March 2013

Removing 4 screws in the base and 2 screws in the handle provides access to the unit. In good condition after 32 years and only needed a quick clean up.

Power Supply
Fairly conventional transformer linear power supply fitted under the plate at the top.

Main Assembly
As well as the 74 series TTL logic, there is a NEC D8039LC 8-bit µP, Motorola MC3410CL 10-bit multiplying D/A converter, Hitachi HN482732AG-20 4kbyte EPROM, and Ferranti ULA2N159E (no information).

Type T Thermocouple
There are a range of thermocouples available for different applications and temperature ranges. The type is designated by a letter: B C E J K M N R S T etc.

A thermocouple is 2 dissimilar conductors in contact which produce a voltage when heated. Used for temperature sensors with 1°C typical accuracy. The output voltage increases almost linearly with the temperature difference. Non-linearity can be corrected. [Wikipedia]

Tables are available that show output voltage in millivolts against temperature in degrees centigrade.

From the label on the rear panel, I'm assuming that the ROM is programmed for Type T thermocouples. Typically for Type T the emf -v- temperature is -6mV at -250°C, 0mv at 0°C and +20mV at +400°C. The conductors are copper and constantan (which is a 55% copper 45% nickel alloy). The plug has slightly different sized pins with the copper +ve and constantan -ve. The thermocouples have a 1m cable length, to extend this special Type T cables are required.


April 2013

Made up a lead with a 3.5mm diameter jack plug to check the data output. This provides a dc output for the channel selected by the front panel switch. So for 24.2°C this provides +251mV on a DMM and Oscilloscope, with a corresponding reduction for the ÷5 or ÷10 range positions.

Checked each channel with a thermocouple and the data output. So in the absence of a Manual, considered to be tested ok.