Scanning rate of Yamatake PM100

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Thread Starter

yoga

I just migrated Yamatake 12 AMC to 5 PM100. The totalizer (summation) of some flowmeters is done by CL by collecting/adding PV in every scan time. With AMC this kind of totalizer is ok for years, but on PM100 sometimes it was found less compared to site indicators or 'manual calculation'. Seems the scanning rate of PM100 is unstable!. Does any one have similar case? Please share.
 
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Robert Scott

It may have been OK for years, but it is still bad design. The scan rate depends on the total complexity of the program. If you change the program, it changes the scan rate. I don't know about the PM100 in particular, but it may very well have some processing that is invoked sporadically, which would extend some scan times. If you need to take the sum of flowmeter readings in order to arrive at a total amount over time, then use a bone fide timer to trigger the summations rather than relying on the uniformity of the scan times.

-Robert Scott
Real-Time Specialties
Embedded Systems Consulting
 
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