need help with alarm design

[sparkytex]

Hello all!

ok all you programmers out there this guy needs a hand programming an alarm for our phosphoric acid storage tank. The tank has a level transmitter scaled from 0-100% level (4-20mA). What was requested was an alarm on the HMI for the operators when the tank drops 2% or greater in level in 6 or less hours. The Address of the floating point number for the HMI indication is
"F8:88". I cant seem to wrap my brain around how I'm going to do this one. Any suggestion would be greatly appreciated!!

thanks, tex

 

[Steve Etter]

The size of your sampling is dependant on how often you want to test. For example, if you want to test once every 15 minutes, you would have 24 samples in a 6-hour long FIFO and compare the current value with the value in the 24th register (the one that's about to be dumped). If you want to test every 5 minutes, your FIFO would have 72 samples in a 6 hour period.

That's where I would start anyway.

Steve

 

[sparkytex]

ok, I see where you're heading. How do you reset a FFL or FIFO when its done all 72 samples?

** edit ** - I realized I could just use a reset off the done bit (R6:2/DN) to enable a Reset addressed to the same Control address (R6:2)

 

[widelto]

Sparky, this file is for SLC but can be applied to Rslogix5k. Take a look at it. Just use the fifo.