Analog input to a float tag

Ecega

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Jul 2018
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I working with a l32e allen bradley and a 1769-IF4XOF2 analog input module,
but when i move the value from channel 0 (current input 4.20mA) to a float tag i cant get the all the values when the current change slow i thing that i need to use some convertion but i dont no what to do.
 
What have you set the channel configuration to ??

The channel input data is an INT value, and a simple MOV instruction to a REAL tag will automatically convert it.

But that is not what you want, is it.

What you really want is the value in your REAL tag to be in Engineering Units of what you are measuring, e.g. -10.0 to 100.0 deg.C

For that you will need to scale the INT value to the engineering units REAL.

The easiest way to do this is to use an Add-On instruction called SCP (Scale With Parameters). Take a look around the projects in the Samples Folders, look for "Add_On_Instructions_Samples.ACD" - you'll find SCP in there, you can Export/Import to your project file.

The Input_Min and Input_Max will be the values you will get from the AI module for your 4 to 20mA range m(and this will be dependent upon your "Data Format" selection), and the Output_Min and Output_Max will be whatever you want the REAL output to be scaled to.
 
Yes i need to scale the value from the input , but the issue with the low resolution in the INT value from the channel 0 is the problem, when i fix a value of current like 4.05 mA the value of the tag is not changing, so i lose intermediate values on the current path.
thank daba for the answer.
 
Yes i need to scale the value from the input , but the issue with the low resolution in the INT value from the channel 0 is the problem, when i fix a value of current like 4.05 mA the value of the tag is not changing, so i lose intermediate values on the current path.
thank daba for the answer.


The Integer data type is not your problem. The low resolution electronics on the 1769-IF4XOF2 analog input module is your problem. That particular module only offers 8 bit resolution.
 

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