SCL with AB and micro 1000 (1761-L20-BWB-5A)

Can anyone tell if I am right on the math for the scl? I am at home now and don't have the math I used in front of me.

The input at I:0.7 is a 4-20 ma input from a card controlled via a pot. All I am trying to do is have 4-20ma input and move same 4-20ma output to O:0.4 when certain conditions are met.

I would have thought I could simply move same raw data from input to output but somewhere in the micro paper work it shows a difference in raw data the micro sees at input and output of same milli amp. In other words the raw data at the input for 4 ma is different than the raw data required at the output for 4 ma.

I have to go out and load this in the morning and would feel better if someone very familiar with the AB micro 1000 analog gave the SCL math their blessing. Thanks.

Not 100% sure

I believe the numbers you are looking for are these, but this may not be exactly right.
4ma 20ma
Input Min = 3277 Input Max = 16384
Output Min = 6242 Output Max = 31208
Hope this helps it should be close.
Memory is not what it used to be!

:site:

For the 1761 Micrologix 1000 Analog the scaling is
Analog Input 4mA= 6241, 20mA= 31207
Analog Output 4mA= 0 , 20mA= 32767

The SCL equation

Scaled value = (input value x rate) + offset

Rate = (scaled max. - scaled min.) / (input max. - input min.)

Offset = scaled minimum - (input minimum x rate)

For the 1761 Micrologix 1000 Analog the scaling is
Analog Input 4mA= 6241, 20mA= 31207
Analog Output 4mA= 0 , 20mA= 32767

Click to expand...

That's what I used to get the values I entered at rate and offset. I believe I did it right. Do my values entered match what you come up with?

I came up with 13125 for Rate -8191 for Offset

in excel

Here it is in excel

Thomas.


I guess what is confusing is that you have to multiply the value you come up with for rate (1.3124) times 10000. It doesnt say this anywhere in the manual.

If you try to enter 1.anything it comes up error "must be integer". I found somewhere else to multiply times 10000 but how are you suppose to know that?

Right on the SCL block "RATE [/10000]"
Also the following is right out of the help in RSLogix 500

Values must be between -32768 and +32767 for the following parameters.
Source must be a word address.
Rate (or slope) is the positive or negative value you enter divided by 10,000 . It can be a program constant or a word address.
Offset can be a program constant or a word address.
Destination is the address of the result of the operation.

Rockwell Software 2000