WIKA S-20 - Manual (Page 9)

9
GB
WIKA Safety manual pressure transmitter, model S-20
14082128.02 06/2014 GB/D/F/E
2.5 Description of the safety function and diagnosis
The safety function of the model S-20 is that the pressure transmitter converts the physical input parameter of pressure
into an electrical signal.
■ The model S-20 recognises the following error states
Error detection Output signal
4 ... 20 mA
(2-wire)
20 … 4 mA
(2-wire)
DC 1 … 5 V DC 1 … 6 V DC 0.5 … 4.5 V DC 0.5 … 4.5 V
ratiometric
Cyclical testing
Underpressure from which
on the error is detected
-2.5 %
Low alarm value
max. 3.6 mA
-6.25 %
Low alarm value
max. 3.6 mA
-12.5 %
Low alarm value
0.2 … 0.5 V
-10 %
Low alarm value
0.2 … 0.5
-5 %
Low alarm value
0.1 … 0.3 V
-5 %
Low alarm value
0.1 … 0.3 V
Overpressure from which on
the error is detected
+6.25%
Low alarm value
max. 3.6 mA
+2.5 %
Low alarm value
max. 3.6 mA
+25 %
Low alarm value
0.2 … 0.5 V
+20 %
Low alarm value
0.2 … 0.5 V
+10 %
Low alarm value
0.1 … 0.3 V
+10 %
Low alarm value
0.1 … 0.3 V
ADC communication error
(within the instrument)
Low alarm value
max. 3.6 mA
Low alarm value
max. 3.6 mA
Low alarm value
0.2 … 0.5 V
Low alarm value
0.2 … 0.5 V
Low alarm value
0.1 … 0.3 V
Low alarm value
0.1 … 0.3 V
Testing on switch-on
Sensor error, EEPROM
checksum error (hardware
error detected by
instrument)
Low alarm value
max. 3.6 mA
Low alarm value
max. 3.6 mA
Low alarm value
0.2 … 0.5 V
Low alarm value
0.2 … 0.5 V
Low alarm value
0.1 … 0.3 V
Low alarm value
0.1 … 0.3 V
Table 2-2: Error detection
■ All failures detected are indicated as downscale alarm signals (low alarm values).
■ Undetected errors can generate an undefined output signal within or outside of the span range.
■ The alarm signal for over- or underpressure is triggered when the error condition exists uninterrupted for a minimum
of 10 seconds.
■ Errors which are checked cyclically are not permanently active, i.e. a reentry into measuring mode after exiting the
error range is possible during running.
■ Missing short-circuit resistance between signals in accordance with table 2-1: Parameters can lead to the destruc-
tion of the pressure measuring instrument. Short circuit leads to the loss of the safety function.
■ The external supervisory logic unit must bring the plant to a safe state if the alarm condition is entered.
2. Safety