High speed pulse input

[bfranklin]

Hey,

In ladder logic how would I convert a high speed counter input into rpm using a control logix processor?

 

[bce123]

what is connected to your high speed input? is it a prox counting teeth on a sprocket? how many teeth are on the sprocket? how many teeth will you count to make 1 rev.?
could you take that # and divide your counter by it? compare it to a 1 min timer? something like that? do you have any ideas to start with?

 

[bfranklin]

A natural gas driven pump, pumps hydraulic fluid into a hydraulic operated pump and we are using a turbine flow meter ( using a magnetic pick up into a HSC input) off of the discharge of the hydraulic operated pump to measure the the RPM.
The turbine meter has a K-Factor of 8003 pulses per cubic meter of fluid.

 

[Ken Roach]

When you say "HSC", do you mean that you are using a 1756-HSC module ?

One of the operating modes of the 1756-HSC is "Rate" mode, whose default values typically give you pulses per second. The User Manual and RA Knowledgebase should include enough information for you to set that up.

The pulses per second of the flowmeter and the K-factor will tell you how many cubic meters of fluid per second are flowing through the pipe, so you need to know some of the parameters of the pump to know how fast it's turning.

What sort of pump is it ? Do you have any information about how many cubic meters per second it pumps at a given RPM ?

 

[Lancie1]

In ladder logic how would I convert a high speed counter input into rpm using a control logix processor?

Do you need the pump RPM for control purposes, or do you simply want to control the pump to produce a certain setpoint of cubic meters per second of hydraulic fluid (or a certain PSI)? If the last case, then the RPM is really not needed (but you might want to display the Pump RPM for other reasons).

If you really do need the RPM, then like Ken and others pointed out, you will need a pump curve showing RPM versus output volume for your exact pump model. Pump curves tend not to be linear, so you would have to use a look-up table, or use a curve-fitting routine to find an equation that calculates the RPM at any given pump output. Even then there probably will be errors for some parts of the pump curve. If it is necessary to have a very accurate RPM, the best solution is to install a tachometer on the motor output shaft.