1.11
1.6.2.3 Microprocessor Board 01100918C or 01100918D
The microprocessor board controls all the functions within the system. It processes digital
signals from the oxygen measuring circuit, temperature sensor and keypad to provide outputs
to the digital display, isolated current output board, heater control and optional relay and data
output modules.
There are 2 versions of the microprocessor board, 01100918C which features a lithium battery
powered memory back-up, and 01100918D which uses a capacitior to maintain the memory
(used on ISSEP INIEX purged analysers only).
1.6.2.4 Current Output Board 01100929A or 01100939.
The microprocessor board sets the zero offset and range of the oxygen signal. The current
output board converts the digital signal to give an 0-20 or 4-20 mA (or reversed) output.
01100939 has a general purpose output; 01100929 and 01100929A are for connection to
intrinsically safe indicators.
Earlier analysers have output board 01100929.
1.6.2.5 Keypad
The keypad contains twenty-one touch sensitive keys which are colour coded to simplify
operation of the keypad. Some of the numerical keys are dual function. The colour codes are
as follows:
Black - Six Keys, used for calibrating.
Green - Four Keys, used to set or display the span range and zero offset of
the analogue input.
Blue - Five Keys, for oxygen level alarm codes.
Grey - Four command keys, a decimal point, minus sign and ten numerical
keys, some of which are multi function.
NOTE: Up to S/N 1101/5199 the colour code for keys was as follows:
Yellow - Replaced by Black
Orange - Replaced by Green
Red - Replaced by Blue
Grey - Remains
1.6.2.6 Display Board 01101902
The microprocessor generates a digital signal to drive the L.E.D. display. This signal provides
an oxygen content reading on the eight character display down to 0.01% oxygen resolution.
The display board also encodes the keyboard signals.
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