RSLogix5000: monitoring a line level with a LIT

Hi again mates,

I've been the whole day squeezing my brains for trying to solve an issue here with the RSLogix 5000...Talking about a tank being filled with water, I'd need to monitor its level line using a level transmitter . I'd need two bits: one going true when the level goes up ("going up" bit) and other going true when the level goes down ( "go down" bit).

I had thought of sampling the input signal, let's say, each 1 minute. The idea here is to sample a level measure and store it in a variable and one minute after do again the same. Then afterwards,right after sampling by second time, compare both to determine if the level has increased or decreased.

I've tried to go with this, but I can't succeed when I try to store the variables.

May someone have a look at my small routine and please give some tips about how to focus this issue?

Thanks in advance to everyone,

Ruben:

Try my approach, variable is your analog data, in this case your level, storage1 and 2 are used to save your variable data.

Thank you Widel! I'll let you know how it went as soon as I check it

Using a function block diagram, you could connect the level input to an analog alarm block. The block calculates rate of change. A positive number is increasing level, a negatice number is decreasing level.