Flowrate

Can anyone supply some sample code to convert a 4-20ma input from a flowmeter into a totalised quantity passing the flowmeter.
Im using an slc505.
Thanks in advance

Because you didnt supply any details on your flowmeter and the type of analog card I will try to explain in generally.

you have to put your Flowmeter data in SCL command in a way you can get real units.
Now put the Min of the flowmeter as 4mA and the Max as 20mA and the
card data and the result in F now you have number which tell you how much liquid go via the flowmeter.

use Compute command to calculate the rest.

All the best

Dont forget to register on this forum.

After I have the flow rate in, say, gallons per minute, using Arik's method I use a self re-setting timer to totalize. You set the time period to give you a reasonable number, and assume the flow rate at the end of the time period has been constant throughout the period. This isn't, of course, true, but unless you are using the total for custody transfer the erors generally cancel themselves out with sufficient accuracy. When the timer times out multiply the current flow rate by the elapsed time and add it to the previous total.

Tom's method plus

In SLCs and PLC-5, I multiply the LAST SCAN TIME (in SLC, S:35) by the scaled flow rate (watching units, of course - last scan time is msec, flow rate may be in min, sec, even hours). This new value gets added to the extisting total flow.

One other alternate to Tom's method is to put the summation logic in an STI program file, and multiply the rate times the STI time to get the total flow in the last time period.