Measure how long a bit stays ON
Overview
Here are two ways to measure ON time, for example when you want to know how long a bit stays ON.
They can also be applied to measure cycle (tact) time and similar.
Method 1: Measuring with Clock Pulses
While the contact is ON, the number of times the 10 ms clock pulse turns ON is counted to measure how long the contact stays ON.
This method is simple, but not very accurate because of errors due to the PLC scan time and the ON/OFF timing of the clock pulse.
However, if the scan time exceeds 5 ms, pulses will be missed, so use the 100 ms clock pulse (CR2005).
Method 2: Measuring with the PLC Scan Time
While the contact is ON, the PLC scan time is accumulated to measure how long the contact stays ON.
The current cycle time is stored every cycle as BIN 16-bit in the measured scan time (10 μs units) (CM720). Since this value is in 0.01 ms units, accumulating it measures the ON time with 0.01 ms precision.
Ladder mnemonics