Reading RPMs by PLCs - Revisited

[jtn]

I have used the high speed inputs built into the base with success on quite a few projects. You may have to go into the configuration of the inputs and set the noise filter to the lowest setting possible to see the pulses if the interval between them is very short. Do the math on the PPM and RPM's expected to see if that is necessary. I've done some pretty fast one axis control with these things before.

 

[allscott]

By the way, each pump is rated 355 cfs or 2656 gallons/sec.

What the heck are these things for? Filling a cities reservoir?

Eye Carumba! I think he must be trying to fill a lake!

Anyway I don't think I understand the problem. If you attach an encoder to the motor and then hook that up to a HSC the HSC will give you a rate indication (HZ) and from that it is pretty simple math to calculate RPM. What's the problem?

 

[OpZed]

Sounds like Edmonston:
http://en.wikipedia.org/wiki/Edmonston_Pumping_Plant

Seems like it would be far better to add a separate DAQ system for what you're trying to achieve. Instead of connecting into the existing control system signals which are still trying to do their jobs. You should add your own which are non-critical and not interconnected.

Since it takes several minutes to start, I can't believe that the shaft speed changes very quickly. So don't you need resolution more than update rate? 0.1 rpm is possible with simple photo reflective.

 

[AnaDigit]

As a matter of fact they are used to maintain city reservoirs filled to capacity.

We move water from water abundant areas as in Northern California, to water thirsty areas like Los Angeles, CA. You can check it out clicking the below link.

http://www.water.ca.gov/state_water_project_home.cfm

- J R Martinez

 

[AnaDigit]

Thanks a lot for keeping my brain-cells moving. You guys Rock!

I think I finally got my RPM detector (and recorder) to work. I learned a lot from reading many posts on the subject as well as reviewing some of the sample code found here and other sites. I wasn't sure what to use, either HSCs or TSI - much less, how to use them. It is the first time I venture into reading RPMs using PLCs.

Bottom line is that I rather use TSI for precision but I want to read 4 sensors with a single PLC; yet, I only have one TSI available in the Function files tree - Unless I can create more and I don't know how.

The PLC will be connected to a laptop running a mini-SCADA data collection system for later analysis specially developed for this test - to read just 4 analog inputs during the initial 5-minutes of every startup. I am not planning to be present when they start those pumps which typically occurs at night when power is cheap.

I plan to follow up this thread with a Lessons-Learned update where I will explain what I did and how, while providing the sample code used hoping others will find useful. The intended audience of the update will not necessarily be those experts on the subject, but rather those that in the future will ask questions about this very same topic.

- J R Martinez