Rockwell Automation 1760-xxxx Pico Controller User Manual - Manual (Page 107)

Publication 1760-UM001D-EN-P - September 2005
Draw a Circuit Diagram with Pico 4-47
Analog Comparators Analog comparators are only available with 12V dc and 24V dc
models. An analog value comparator or threshold value switch
enables you to compare analog input values with a setpoint, the
actual value of another function relay or another analog input. This
enables you to implement small controller tasks such as two point
controllers very easily.
• The analog inputs of the 1760-L12 are I7 and I8.
• The analog inputs of the 1760-L18 and 1760-L20 are I7, I8, I11
and I12.
Pico provides sixteen analog comparators ‘A1’ to ‘A16’.
A comparator can perform six different comparisons. The relay
contact switches if the comparison conditions are true.
• I7 greater than or equal to I8, I7 less than or equal to I8
• I7 greater than or equal to setpoint, I7 less than or equal to
setpoint
• I8 greater than or equal to setpoint, I8 less than or equal to
setpoint
Both the setpoint value and the actual value correspond to the
measured voltages.
The resolution of the voltage values from 0.0 to 10.0V dc is in 0.1V
steps.
If the voltage at the input terminal is above 10V dc, the comparator
value stays at 10.0V dc.
You can enter the setpoint values for a comparison while you are
creating the circuit diagram or in the parameter display in Run mode.
A typical application would be to evaluate the analog values of
sensors, e.g. to measure pressure or temperature.
IMPORTANT
Compatibility with Pico Series A Controllers:
If you have loaded an existing Pico Series A circuit
diagram, the previous comparator functions and
values are retained. The analog value comparator
function relay can work in Pico Series B Controllers
in the same way as in Series A Controllers. The
setpoints are converted to the new resolution of the
analog inputs.