40-71 Doc PS Rev Rb Instrumentation, analogue signals
and threshold detection (3) Digital instrument reading. Signals can be active high or low and
shallhave the facility for being time filtered on both rising and falling edges.
(4) Analogue instrument reading and scaling of all common signal types the scaled values
willbe real
numbers the input signals willinclude:
1 Voltage (±10 V, ±5 V, ±1 V, ±500 mV, 1-5 v)
2 Current (±20 mA, 0-20 mA, 4-20 mA)
3
RTD (150 Ω, 300 Ω, 600 Ω, 6000 Ω, PTx00, Nix)
4
Thermocouple (types BK, NR, ST) Detect analogue instrument faults (wire break, over range, under range c.
(6) Analogue signal threshold detection for process events (i.e. triggers some action when a particular signal value is reached, these can be triggered for both
low and high thresholds and shallhave the facility for being time filtered and
willhave hysteresis filtering to prevent nuisance
“chattering”triggers.
(7) Conversion and scaling for analogue outputs (converts areal value to a standard fixed integer range suitable for the analogue output.