Flow Sensor Transmitter scaling

[Snap25]

By default my transmitter (GF Signet 9900) is scaled 0 GPM (4mA) - 100 GPM (20mA). I'm trying to figure out how determine my max value to get the best resolution and accuracy.

The diaphragm pump being used is rated at 17 GPM max. So I tried that and the live GPM just seemed off so tested it and the totalizator and actually gallons was off by a lot! I tried a few other values and every values changes the live GPM value significantly

0 - 40 GPM?
0 - 50 GPM?
0 - 60 GPM?

There has to be a way to determine what it should be set at instead of trail and error and testing until I find a value that is close to the real gallons (I'm pumping water out of a 55 gallon drum to another 55 gallon drum as my data point as my "real" gallons).


Tried looking in the manual, didn't find anything. Give Georg Fischer a call was my next move but I wanted to see what you fellas thought!

Thanks

 

[osmanmom]

are this transmitter suitable for your diaphragm pump application ?

 

[Snap25]

Well I took a look in the flow sensor manual an found the max flow rate is 20 ft/s. It's a 3/4 dosing line so that would be a 34 GPM max rating for the flow sensor..

Is that what my max should be?

 

[Snap25]

are this transmitter suitable for your diaphragm pump application ?

Yes, the placement of the flow sensors is in a good location. The sensor is 50x the I.D down stream of the pump with no elbows between the two (recommendations from the flow sensors manual)

 

[danw]

The scaling on the transmitter has to match the scaling in the PLC/HMI.

If the flow meter is 0-100gpm, then the PLC/HMI has to interpret that as 0-100gpm or it's garbage data.

Are you changing both scales - transmitter scale and PLC scale in this effort for better resolution?

 

[Paullys50]

The scaling on the transmitter has to match the scaling in the PLC/HMI.

If the flow meter is 0-100gpm, then the PLC/HMI has to interpret that as 0-100gpm or it's garbage data.

Are you changing both scales - transmitter scale and PLC scale in this effort for better resolution?

Pay attention to this.

Also, what is the resolution of the analog card you are using? This could be a factor as well.

 

[Snap25]

The scaling on the transmitter has to match the scaling in the PLC/HMI.

If the flow meter is 0-100gpm, then the PLC/HMI has to interpret that as 0-100gpm or it's garbage data.

Are you changing both scales - transmitter scale and PLC scale in this effort for better resolution?

That is correct, I'm changing both scaling values in the PLC and transmitter..

The live GPM value does change when I adjust the max GPM scaling (in both) but they both display the same value but I'm trying to determine what my accurate flow rate is and to determine that I feel like I need a correct max GPM

 

[Snap25]

Is my thought process wrong? Does it not matter what my max value it in my scaling? As long as its the same in both the transmitter and plc scaling?

 

[Bullzi]

It depends on what you want to do. If you are just looking to display the Flow on a HMI, then the It doesn't matter what the high end is set for as long as it is the same in the PLC and the Meter. Within reason of course. You wouldn't want to set it to 0-10,000 GPM if you cant flow more than 100 GPM.

If you are doing some control with the flow rate and need a fine resolution then you will want to tighten up the range to fit your actual flow conditions. For example If the absolute max flow your pump can deliver is 85 GPM then 0-100 is not a bad scale. If it is say 50 GPM then you might want to change the scale to 0-60GPM in the PLC and Meter. You always want to have your high end a little bigger than the maximum the system can deliver.

 

[Snap25]

It depends on what you want to do. If you are just looking to display the Flow on a HMI, then the It doesn't matter what the high end is set for as long as it is the same in the PLC and the Meter. Within reason of course. You wouldn't want to set it to 0-10,000 GPM if you cant flow more than 100 GPM.

If you are doing some control with the flow rate and need a fine resolution then you will want to tighten up the range to fit your actual flow conditions. For example If the absolute max flow your pump can deliver is 85 GPM then 0-100 is not a bad scale. If it is say 50 GPM then you might want to change the scale to 0-60GPM in the PLC and Meter. You always want to have your high end a little bigger than the maximum the system can deliver.

Thanks, that clears it up a little for me.

Pump :

Max Flow Rate : 17 GPM @ 8 bar

I have the regulator set at 2 bar so my flow should be around 4.75 GPM on average.

I currently have it scaled in the transmitter and PLC at 0 - 40 GPM and the live GPM display is pretty close to what I assume should be the average GPM based off of the setting of the regulator. I will run it through my totalizer and pump from drum to drum and see what kind of numbers i get.

 

[Bullzi]

You could drop the scaling to 0-20 and get better measurement as the resolution will be finer.

As for totalizing, I hate totalizing off the 4-20mA signal. I know it can be done but it is just one of those "nails on the chalk board" things. Most likely caused by being in the Oil Measurement business for over 25 years Does the meter have a pulse output that you can use for totalizing? I just finished a job with meters that had HART and I would pull in the meters totals over HART and that worked pretty good too. Again I guess it comes down to how accurate do you need to be??

 

[Mickey]

Double check the K-factor for the meter. Make sure you have set this up in the transmitter correctly.

 

[Snap25]

Double check the K-factor for the meter. Make sure you have set this up in the transmitter correctly.

The K- Factor is correct. I triple checked the pipe size and the k-factor on the sheet to make sure I entered the right figure.

I think I have it set up correctly right now, I will find out more once they run it tonight.

 

[Snap25]

You could drop the scaling to 0-20 and get better measurement as the resolution will be finer.

As for totalizing, I hate totalizing off the 4-20mA signal. I know it can be done but it is just one of those "nails on the chalk board" things. Most likely caused by being in the Oil Measurement business for over 25 years Does the meter have a pulse output that you can use for totalizing? I just finished a job with meters that had HART and I would pull in the meters totals over HART and that worked pretty good too. Again I guess it comes down to how accurate do you need to be??

I'm totalizing with a Dosing AOI I created.. which I think gets me pretty close ( +/- 2%) They never dose more than 100 gallons at a time and most of the time they are dosing from acid from a 55 gallon drum so they will just enter 100 gallons and pump it until the no flow alarm comes on.. so really I'm wasting my time thinking about this to much!

In the future, I'm going to start using the transmitter to assist me in totalizing.

 

[widelto]

Snap25: Is your pump principle similar to spitting like bursts.?