D395-90-880 Issue E
Page 10
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INSTALLATION
3.3.3
Connecting the analogue / relay connector (enhanced only)
The analogue / relay connector provides two relays for control of your own equipment, and analogue outputs which
can be used for recording the gauge signals.
3.3.3.1
Using relays
The two relays are volt-free single pole change-over types. Relay 1 is controlled by gauge 1, and relay 2 is controlled
by gauge 1 or gauge 2. The relays are energised when the indicated pressure of the relevant gauge falls below the
set-point low threshold, and de-energised when the pressure rises above the set-point high threshold. The threshold
values are independently set using the front panel keys (see
). The LED indicators on the front panel are
lit when the relays are energised.
3.3.3.2
Using analogue outputs
Two analogue outputs provide the gauge signal voltage for monitoring or recording purposes. These can be connected
to a chart recorder or other similar equipment. The outputs are buffered to prevent disturbance of the gauge signal,
and will follow the gauge signal to within the accuracy specified in
.
3.3.4
Connecting the serial interface (enhanced only)
The ADC has an RS232 interface built in, which allows a host PC to control the ADC.
The ADC is fitted with a 9-way 'D' type socket on the rear panel. The interface uses two lines for data transfers and
an additional line as a signal common. Hardware handshaking is not implemented.
If connecting to an IBM compatible PC fitted with a 9-way D' type socket then a 'straight through' male-female 9-way
extension cable can be used to connect the ADC to the computer as shown in
. Connection to an IBM PC fitted
with a 25-way serial connector should be made as shown in
Use shielded cable for the interface to reduce interference problems and limit the length of the RS232 link to less
than 10 metres. For longer links, install line drivers.
Figure 8 - IBM PC RS232 interface - 9-way
Figure 9 - IBM PC RS232 interface - 25-way
WARNING
Do not connect the relays to voltages greater than 48 V d.c.
Do not use the relay outputs for safety purposes.
