Endress Hauser Flow Meter 4-20ma

mavrick said:

I am currently using the compute instruction with this formula below to get my total:

(mag register/60+HMI total) ex. 250gpm/60+600 gallons this is pulsed every 1000 ms by a timer dn. bit. and the accumulation is showed on the HMI screen.

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I'm slow, so please explain like you would to a child why the total calculation is summed value of flow rate/60+600 and not the summed value of flow rate/60?

Why does total calculation add 600 gallons?

Does the E&H display a flow rate? When the product is flowing does the flow rate displayed on the E&H match the scaled flow rate from the analog input signal that the PLC uses for its calculations?

danw said:

I'm slow, so please explain like you would to a child why the total calculation is summed value of flow rate/60+600 and not the summed value of flow rate/60?

Why does total calculation add 600 gallons?

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600 is an example of the running total (i.e. accumulating total), HMI total, from the symbolic formula (mag register/60+HMI total)

That formula is what the CPT, which is doing the totalizing, calculates, and then puts the result back into HMI total.

When the OP typed 250gpm/60+600gal, that was intended as an example of the running total formula with actual numbers (and not a calculation of the instantaneous flow) that could happen on one rung i.e. when the accumulated value from previous executions of the CPT instruction (HMI total) is 600gallons, and the flow (mag register) is 250gpm.

@DrBitboy, thank you for that clarification.

So I simulated the signal from the meter to the input card. Everything matches.

(4ma=0Gpm and 20ma=400Gpm).

With E&H i was able to simulate 4-20ma and 0-400GPM to make sure everything was registering correctly in my input card.

I also cleaned the electrodes in the meter they where very dirty. After confirming all signals and cleaning I still could not get the totalizer to repeat any totals. Sometimes it was spot on , some times it is 72 gallons less than spt. and some times 90gallons more than spt.

I believe i'm going to switch out the flow meter and see if it helps. I may even try setting up the meter for pulse. I'm completely out of options. I tried periodic task, etc.

Dr.bit boy i appreciate all your help, but some of the examples are bit over my head. I have used the GSV instruction. But i'm not 100% following what you have listed as examples. Unfortunately i don't get to work with logic all the time and it puts me behind.
I appreciate all the help!

So I simulated the signal from the meter to the input card. Everything matches.
(4ma=0Gpm and 20ma=400Gpm).

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But when the material is actually flowing and the E&H says its flowing at 200 GPM (for example) are you getting 12 mA at the analog input? Use Studio 5000 to set up a trend chart of the analog signal over a full batch and see how noisy the analog signal is.

Yes that is correct. At 12 ma the analog input will show 200 GPM.

Does the totalizer on the Meter show the same qty of change as the total on the HMI when there is an offset?

If so, maybe you have a problem with the valve or actuator really at the root of this?

I tried using a offset and still had the same problem. The meter totalizer would be correct but controller totalizer would be off.

mavrick said:

Yes that is correct. At 12 ma the analog input will show 200 GPM.

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At 12mA, does the flow meter show 200 as well? Or was that test done with a signal generator?

mavrick said:

I tried using a offset and still had the same problem. The meter totalizer would be correct but controller totalizer would be off.

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How do you know the flow meter totalizer is correct?

Yes the flow meter shows 200 gpm at 12 ma. I feel the totalizer on the meter is correct because we have verified our signals to and from the meter are correct.

mavrick said:

Yes the flow meter shows 200 gpm at 12 ma. I feel the totalizer on the meter is correct because we have verified our signals to and from the meter are correct.

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Okay, then do we know if the clock on the flow meter is accurate?

And does a 700gal batch at 250gpm take about 2m48s, and a 1500gal batch at 250gpm take about 6m0s, to within a couple of seconds as measured with a calibrated timer (you said the flow goes from 0 to 250gpm in 2s)?

I'm not aware of any clock on the flowmeter. And yes the times match up per batch.

mavrick said:

I'm not aware of any clock on the flowmeter. And yes the times match up per batch.

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If it is totalizing from the flowrate, it must use a clock.


If it is totalizing from a pulse but the pulse is generated based on a flowrate (e.g. coriolis or sonic meter), it must use a clock.



If it is totalizing from a pulse and the pulse comes from a volume displacement devuce, then it should be able to get away without a clock.


But if the batch completion times are right, the clock is probably not the problem.


Can you sample the PLC's data (mag gpm, HMI total) every 15s or so over a batch, and post it here (e.g. .xlsx in a .zip file)?