Inputs
17
Sensor check for analogue sensors
When
"Sensor check"
is active (setting:
"Yes"
), a short circuit or a lead break will
automatically
gen
-
erate an error message.
Example:
Sensor error
When
"Sensor check"
is active, Sensor error is available as an input variable for functions: status
"No"
for a sensor that is working correctly and "Yes" for a defect (short circuit or lead break). This allows
the controller to react to the failure of a sensor, for example.
In System values / General, a sensor error for
all
inputs is available.
If the
Standard
thresholds are selected, a short circuit will be indicated if the value falls below the
lower
measurement limit
and a lead break will be indicated if the value exceeds the upper
measure
-
ment limit.
The
Standard
values for temperature sensors are -9999.9 °C for a short circuit and 9999.9 °C for a
lead break. Those values are utilised in the internal calculations in the event of an error.
By selecting the thresholds and values appropriately, a fixed value can be specified for the controller
in the event of sensor failure, in order to allow a function to continue operating in emergency mode.
Example:
If the temperature value falls below the threshold of -40 °C (= "Threshold value"), a value of
0.0 °C (= "Output value") is issued and displayed for that sensor (fixed hysteresis: 1.0 °C). At the same
time the "Sensor error’ status is set to
"Yes".
Example:
Sensor 1 has fallen below -40 °C, so 0 °C is issued as the measurement, and a sensor error
is displayed at the same time.
