
8
Description of Reader Unit
The Reader Unit is housed in a tough, durable, high impact polycarbonate case with a keypad and alpha-numeric
display mounted on the front panel. The side of the case has five connectors. The top connector is used for data
output, the second for connecting an external power supply and the third is the sensor connector. The two
remaining connectors are used for auxiliary analog probe inputs and a GPS input. Each connector is provided
with a protective cap which screws over the connector ensuring full waterproof sealing. The connectors also
have a polarising pin so that incorrect connection cannot be made. Inside the Reader Unit a CPU controls the
operation of the instrument, memory stores data and 8 C size rechargeable batteries power the instrument.
Connector Pins
The connector pins on the Reader Unit connectors are numbered in clockwise order from the polarising pin (see
figure 1). The following table lists the purpose of each pin on the connectors.
Communications Auxiliary Power 611 Sensor
Pin 1
Ground
Negative
Ground
Pin 2
RS232 out
Positive
Data
Pin 3
RS232 in
n/a
+12V
GPS
Auxiliary Sensor 2
Pin 1
Ground
Ground
Pin 2
Signal 0-5V
Signal 0-5V
Pin 3
+12V
+12V
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