cumulative timer in CCW

I am a rookie looking for direction, not handouts.

I need to calculate the time on of an input (sensor) and compare it with the time on of another. I have the TDF function and compare function figured out, just not sure on the cumulative timer? can I used the elapsed time of an RTO to use as the time variable for the TDF?

I would just use math instead of timers. Use the system pulse bits to keep track of when the inputs are on / off independently. Use the 0.1 second pulse and the input to add to a word. Use different words depending on the conditions.

Regards,
Garry
http://www.accautomation.ca

It depends how long your inputs are going to be on for. A TDF function works off the free running clock, which only counts to just over 10 seconds.

I would use a RTO on each input, then use math instructions to compare the ACC in each timer.

the Inputs will be on for about 750ms, then off for 1.5s. I need to output when there is more than a 50ms difference between the two.

http://www.accautomation.ca
I am not sure on your CPU, but here are my thoughts.
If you can fix the scan rate of the PLC, then count the number of scans.
Some processors will have a register with the current scan time. Use this to add the time.
Regards,
Garry