MicroLogix 1000- Analog Scaling

Hello everyone, Whats a good way to scale analog in a micrologix without a SCP instruction. Thanks for your help

Read Chapter 6 of the manual for SLC analog inputs.

Analog Scaling

There is an example using standard math.

Rockwell programmers

I've never been fond of the method that Rockwell shows in that manual.

A better way is to do the same calculation that the SCP instruction uses:

((INPUT - INPUT_MIN) / (INPUT_MAX - INPUT_MIN)) * (SCALED_MAX - SCALED_MIN).

If you are using variable addreses for the parameters, then you'll need two intermediary registers for you calcuations. If you are just using constants, then it becomes easier.

You could also just use the SCL instruction (which is available in the PLC).

And before you ask, the two values would be:

RATE = 10000 * (SCALED_MAX - SCALED_MIN) / (INPUT_MAX - INPUT_MIN) ;

OFFSET = INPUT_MIN * (RATE / 10000)

Here's an example using the SCL function.