analog conversion anomaly slc 500?

bright676

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Join Date
Nov 2012
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va
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I have a program that has a scp of 0v to Image dc and in the input minimum it has 1638 and the input max is 14736.

The scaled min is 0 and the scaled max is 500.'

The pressure transducer range is 0.5v to 5v.

The only info that I can find on the transducer is on the schematic that says 0.5v to 5v.

This machine is about 12 years old and the have been complaining at least 8 years that the pressure is reading is about 25 - 30 psi to high on the panelview.

My question is about the input minimum of 1638. Does this seem like it is correct? I thought it should be 0 as in the accompanied chart. Am I wrong?

Thank you.

conversion.PNG
 
Last edited:
I assume you mean that the input range of the input module is 0-10VDC.

Much of this depends on the sensor. If the sensor really does put out 0.5VDC at 0 PSI then the value of 1638 at 0 PSI is correct (0 PSI = 0.5 VDC = 1638 counts). It is the top range I am concerned with. If 500 PSI = 5 VDC the upper value of the input scalar should be 16384. 14736 bits equates to 4.5 VDC. I think I just saw the error of the programmers ways. The SCP isn't looking for the range between the lower and upper input pair, it is looking for the lower and upper values themselves. I think if you change the 14736 to 16384 things will begin to look a little better.

Keith
 
You need to double check your transducer also. A lot of ratiometric voltage transducers will output 0.5 to 4.5 volts.
 

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