INFO
If you choose a
Pt100
pre-configured curve, for the sensor output you must select
Pt100 ohm
. Similarly, if you choose a
Pt1000
pre-configured curve, for the sensor output you must select
Pt1000 ohm
.
Sensor failure
You can configure customised alarms for sensor failure. The
Below range alarm
is activated when the analogue input is below the
specified value. Similarly, the
Above range alarm
is activated when the analogue input is above the specified value.
INFO
Do not use the sensor failure alarms to respond to ordinary operating data. Configure customised analogue input alarms
instead.
Supervised binary input
Analogue inputs used for supervised binary inputs should be configured using the sensor output
Dry contact
.
Use an analogue input curve to define the supervised binary input. As shown in the examples, for the supervised binary input the
curve is a step function. That is, the curve consists of a horizontal line (with the value 0 or 1), a vertical line (the point where the
curve changes), and another horizontal line (with the value 1 or 0).
If the sensor output corresponds to the change point, the controller uses the last point specified in the curve. For the
Supervised
GB short circuit example
, if the sensor output is exactly 150 Ω, then the function input is 0.
To avoid instability, configure the curve so that the change point is far away from the input closed and open values.
If the analogue input measurement corresponds to a function input that is
not zero
, then the controller uses
one
as the function
input.
Supervised GB short circuit example
The designer creates the following wiring for a
GB short circuit
digital input:
COM
200 Ω
50 Ω
GB short
circuit
When the
GB short circuit
is open, the circuit has a resistance of around 200 Ω. When the
GB short circuit
is closed, the
circuit has a resistance of around 40 Ω (the combined resistance of the 50 Ω and 200 Ω resistors in parallel).
If the
GB short circuit
digital input is activated, the controller activates the
GB short circuit
alarm.
The designer configures a customised function curve with an output of
1
up to 150 Ω, and an output of
0
above 150 Ω. The
short circuit sensor failure is below 5 Ω. The wire break sensor failure is above 250 Ω.
DESIGNER'S HANDBOOK 4189340911K UK
Page 419 of 521
