Created Date: December 09,2003

Created by: eran

I am measuring flow with a flow meter that gives me pulses as an output. The meter is not linear so we had to linearize it over 10 points. Currently the flow meter is connected to a red-lion display that has 10 linearization points and it is working nice. I now want to connect the meter to a PLC.

I am planning to connect the meter output to a high speed counter on the DL-06 and count the pulse over 1 sec to calculate the rate.

My question is regarding the linearization. What would be the best way to calculate the flow as the flow factor changes depending on the rate (e.g. at 1-LPH the factor is 76.54 and at 2-LPH the factor is 77.89 and so on).

Any help in this matter will be appreciated.

Created Date: December 09,2003

Created by: JimHoward

Put your instrument data in two columns, into Excel.

Chart (graph) the curve as XY scatter, with points connected.

Select the chart, go to the Chart menu, and "Add Trendline ". Select a 2nd (or maybe 3rd) order polynomial. Click the box "Display equation on chart ".

Now you have an equation that fits the output curve of your meter, which can be reproduced in your PLC ladder logic.

Created Date: December 09,2003

Created by: eran

I believe this will work nicely, however, I am looking to a more flexible approch.

The flowmeter unit is installed at the client site and once a year the meter will have to be re-calibrated. The re-calibration will produce new points and the client doesn't have the means to change the formula.

I am wondering if there is another way to linearize the meter.