pulse input to GPM question

I am a newbe and I have read alot about this topic, however, this is kicking my butt. I have a Allen Bradley SLC5/3 with a HSCE high speed counter module installed. The original program is using this as a totalizer. Its using a CPT function as such,I12.2*1000+I12.3 which I read in the manual is converting to a floating point. I need a direct GPM reading taken from the same input. The problem I am having is gathering 1 second of data. I read the output of the flow analyzer with a o-scope and its outputing 6 pulses per 10ms at 550GPM. I converted it and I got .00152 gallons per pulse. I figured if I could capture 1 second of pulses multiply that by .00152 then multiply that by 60 I would get my GPM. I have tried all kinds of stuff, it seems like the high speed counter will count 10 seconds worth of pulses and then reset. What am I missing, I am sure I will probably shoot myself when I get the answer but I need some help.

What type of flow measuring device are you using. You should be able to go into the configuration of the flow measuring device and see what the pulse output in configured for. It sounds like you are using a magnetic or possibly a mass flow meter.

Its a Seimens SITRANS FUS1010

The factory manual should tell you how many pulses per unit
say revolutionn if rotary.

You must know the design and the calibration data.

You can then confirm with O scope sensor is operating properly.
Knowing that you can then determine if PLC is getting right signal.
Then assuming the right PLC module you can change the "calculations" to get the number you want

Dan Bentler

I think the OP's question is how to get the A-B to count pulses for 1 second, from which he could then calculate the flow rate over a minute.

It seems the high speed pulse input card to do anything other than count for 10 seconds and then resets, which is not acceptable, however multiplying the 10 second accumulated pulse value by 0.00152*6 would yield value in gpm, but at a 10 second refresh rate.

Danw that is a correct response. I just now need to capture the 10 sec counts. The refresh rate will not be an issue this gpm reading is not controlling anything only indication. I will post if I succeed or not. Thanks

Are you using the 1746-HSCE card? I have used this in the past and word 3 gives you the frequency (Hz) of pulses.

The math you show for the totalizer and "converting to a floating point" doesn't jive with this that's why I ask if this is the card you are using.

This is from the 1746-HSCE user manual:


Flow rate (gpm) = I:12.3 * 60 * number of gallons per pulse

The accumulation (word 1) resets if the counter rolls over or a reset is executed by the software. Word 2 will reset at a rate defined by the Rate Period. This is the accumulated pulses per rate period, used to calculate pulse frequency (word 3).

gmferg
I believe it is a 1746-HSCE card. I am not sure why the original program has the calculation multiplying by 1000. I did not put the rest of the calculation in my original post,it has another CPT block that is dividing the multiplied number by 60 to get the totalizer number. I did have a chance today at work to get back online and play with the numbers. I opened the I:12 input file and it was reading in binary, I changed it to decimal and seen where I:12.5 was reading the flow in GPM. So there was the number I was looking for right in front of me. Thanks alot for the replies. This forum is really great for people like me who are not really experts but are all some companies have that need to get the job done (or try). Thanks again