Oil contamination (Particle counter)

Hello,

I am working with a hydraulic power unit where there is installed a particle counter. signal i get on the PLC is 4-20 mA which comes in 5 pulses. each pulse longs for 2 seconds and after each 5 pulses there is pause for 30 seconds.

I need to get all 5 values and show it on a HMI (operator panel).

Can somebody help me with that, an algorithm for example?

See attached document for details about the signal.

Thanks in advance

Regards
Babar

I would initialize by dropping out the logic for a bit I would call the "Sync'd" bit.

If the syn'c bit is not set you may chose to null out some values or leave old values in place.

In order to set the sync'd bit, just set a range check on the analog signal to be 20ma. I say range check because it is often found that the digitized signal may have some jitter.

Once you have the start signal you can set the Sync'd bit, or seal it in, and start the timed sequence. I would just use one timer and set ranges for it's accumulator to take a snapshot in the middle of where each data point should be.

So, after the 20ma drops out, start your timer and snag data when its accumulator crosses boundaries of 3 seconds, 7 seconds, 11, 15, and 19 seconds to capture data items 1 though 5 respectively, then circle back to the state where you are waiting for the 20ma start signal to drop out again...You can do a check on the zero signal to ensure validity as an additional state or states between each data point if you want.

That is the approach I would take, just find the end of the start signal and start one timer, take snapshots where the data should be at each point in time, repeat.

Interesting abuse of an analog signal.

Try this:

And the actual program:

Thanks

thank you very much. i will try it and let you people know.

Anytime! Enjoy!