Functionality - ABB AC500-S Safety User Manual

AC500-S Safety Modules
AI581-S analog safety input module > Functionality

3.5.2 Functionality

Analog inputs
LED displays
Internal power supply
External power supply
Self-tests and diagnostic functions (both start-up and runtime), like CPU and RAM tests, program flow control
and cross-talk tests, etc. are implemented in AI581-S according to IEC 61508 ed. 2 SIL 3 requirements.
AI581-S contains 4 safety analog input channels with the following features:
n 14 bit resolution
Checking of process power supply (Diagnostic message is sent from the Safety I/O module to the CPU
n
informing about the lack of process power supply for the given Safety I/O module). This function is a non-
safety one and is not related to the internal safety-relevant over- and undervoltage detection.
Noise rejection 50 Hz or 60 Hz
n
n 1 channel (0 ... 20 mA), 1 channel (4 ... 20 mA) or 2 channel (4 ... 20 mA) modes (minimum or maximum
value can be selected for transfer to Safety CPU in 2 channel (4 ... 20 mA) mode; Tolerance range
4 % ... 12 % can be set for 2 channel mode)
NOTICE!
In a 2 channel mode, the lower channel (channels 0/2 ➔ Channel 0, channels 1/3 ➔ Channel 1, etc.)
transports the aggregated process value, PROFIsafe diagnostic bit, acknowledgement request and
acknowledge reintegration information. The higher channel always provides the passivated value "0".
NOTICE!
The maximal internal discrepancy time between two channel values in AI581-S module is 67.5 ms,
which is also an internal worst-case input delay value.
NOTICE!
The analog input channels have built-in hardware low-pass filter of 100 Hz.
NOTICE!
In case of the overcurrent/undercurrent detected at the safety analog input channel, the channel passi-
vation takes place latest after 200 ms. The channel remains passivated for 30 seconds and then the
check is performed if the overcurrent/undercurrent still present or not. If the overcurrent/undercurrent
has gone, then reintegration request signal for the given channel is set to TRUE to allow channel rein-
tegration.
The following table shows the mapping of Safety CPU process values to the values in mA from AI581-S
module. Two modes are defined for an analog input 0 ... 20 mA and 4 ... 20 mA.
138
4 (0 ... 20 mA or 4 ... 20 mA)
for signal status, module errors, channel errors and supply voltage
through the expansion bus interface (I/O-Bus)
via the terminals ZP and UP (process voltage 24 V DC)
AC500-S 30.03.2017