Analog Readings in contrologix

Hi everyone.

I have a question about analog devices and the value that the Plc reads. Do all vain slog devices give the Plc a reading between 0-30800, that's the raw signal and then I do the scaling with whatever range I have it set to?

Or does my raw data for an analog input vary between that.
So my 4ma will always be raw data of 0 and my 20ma signal will always be raw data of 30800? The I do with it what I want in the Plc?

Thanks.

The data format and scaling depends on the Analog Input module.

In general, the more platform-specific the module is, the better it integrates. 1756-series analog modules have onboard Engineering Units scaling, in which you manually set the values that are equivalent to 20 mA and to 4 mA. Often these are floating point values, which leads to a very easy-to-use engineering value that directly represents kilograms, meters, newtons, degrees, etc.

Modules that are intended for use with multiple platforms, especially older ones, tend to have fewer configuration options and report their value in "counts", which requires you to write ladder logic to perform engineering unit calculations.

The SLC-500 family controllers had a very popular ladder logic instruction called "Scale With Parameters", into which you just plugged the min/max values for the raw counts and the engineering units.

ControlLogix has the "Scale" function block that does a similar thing. Because it's not available in the Relay Ladder Logic language, many subroutines and Add-On-Instructions have been developed to emulate the popular SCP instruction from the SLC-500 family.

vain slog devices

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?

Raw data depends on the analog card and how you configure them.

See page 52..

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1756-um009_-en-p.pdf

Do all vain slog devices give the Plc a reading between 0-30800

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Mickey, Translation of dhuber's editing-that-went-astray: "Do all [analog input] devices give the Plc a reading between 0-30800....

Lancie1 said:

Mickey, Translation of dhuber's editing-that-went-astray: "Do all [analog input] devices give the Plc a reading between 0-30800....

Click to expand...

Thanks.