Pilz PSSu E F AI I - Manual (Page 13)

Function description
Operating Manual PSSu E F AI I(­T)(­R)
21981­EN­05 13
4 Function description
4.1 Module features
4.1.1 Function description
Module supply
} The module supply provides the module with voltage.
Input signal processing
} The analogue input signal is prefiltered, amplified and stored as a digital measured
value.
} A "dynamised" value is also generated. This value is formed from the sum of the meas­
ured value and a test value.
} For the feasibility check, the test value is subtracted from the measured value. The
measured value that has been read in is then compared with the "dynamised" value.
} The feasibility of the value is checked in the head module. It is feasible if it varies at
most by a small, defined tolerance value.
} If the difference between the two values lies within a certain tolerance, the measured
value is valid. If the difference lies outside that tolerance, the measured value will be re­
recorded. If this value also lies outside the tolerance, an error message will be issued.
Schematic representation of signal processing:
Input
Micro-
controller
FS
module
bus
Analogue
Digital
Analogue
Digital
Head
module
Resolution of analogue­digital converter
} The resolution of the analogue­digital converter is 12 bits and therefore has 4096
quantisation levels.
} With 1­channel operation, a resolution of 16 levels is safe and tested.
} The safety­related accuracy within the module is max. 5 % of the measuring range limit
value. It must be considered across the whole measuring range, particularly in the zero
point range.