View Full Version : slc500_tank level_pounds

April 15th, 2008, 11:13 AM
with a slc500 plc, if you have a tank that holds water, and has a pressure transmitter at the bottom of the tank that will give 4-20ma if tank is empty or full.
When full the tank holds 70,000 gallons of water. So 20ma = 70,000 gallons.
I experimented on the bench with a slc500, can use the scp instruction to take the 4-20ma input (0-16383) to show 0-100%

How can you show the pounds, since you can not use a number about 32767 without faulting the plc?
Under data files, you can not have a Long, which is what I have used in the past with the micrologixs 1200.

April 15th, 2008, 11:19 AM
Which SLC 500 do you have. If it supports floating point. Then use that
( floating point i.e. F8:0)

April 15th, 2008, 11:19 AM
Is the lb. measurement going to be shown on an HMI? I would take the value and divide it by 10, and then send it to the HMI, where you can then multiply by the tag by 10 when being displayed and get the original value back.

A bit crude but it seems to work.

April 15th, 2008, 11:22 AM
Multiply gallons by 8.33 and store the result in a floating point.

April 15th, 2008, 01:11 PM

will try the suggestions.
I have a slc505 processor.