PID VI - Output Range Question

I have a question concerning the PID VI and it's output range option.
"What is gained or lost from using 0-100 versus -100 to 100 for a default output range?"
My application:
My application provides the PID VI a setpoint and a process variable, both in degrees Celsius. I see that the output from the VI has a default range of -100 to 100. The power supply that I want to power accepts an input range of 0.0035 - 0.020 mV.
If I simply enter that range into the VI, the output is either zero or 0.020.
I can get other values if I use the larger scale and then convert them to the smaller numbers. I am trying to decide between using the range 0 - 100 or going with the default range of -100 to 100 and simply cutting off anything below zero in the conversion to mV. What is gained or lost from using 0-100 versus -100 to 100 for a default output range?
Thank you
-Ron

Here is an example of the four situations.
Thank you,
-Ron
Attachments:
PID Single.vi ‏129 KB

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Hi,
I'm trying to understand what is the proper way to define a PID output range. here is the problem:
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Solved!
Go to Solution.

Hi shayelk,
the result of negating P would practicaly be similar to multiplying the output by -1, right?
Well, negating P changes the direction the PID control works. It's like changing from a heater to a cooler…
What do you mean by "provide the manual control at all times"?
From the help of Advanced PID:
manual control specifies the value of the control output when auto? is FALSE.
When auto? is FALSE, this VI uses manual control. This VI uses bumpless transfer from manual control to automatic control.
When the PID is off (auto?=FALSE) it will output the value wired at manual control. When switching to auto?=TRUE it will not jump to a new output value, but will "sweep" to a new value as is said: bumpless…
I think that's what you want: when activating the PID it should start with the last value provided by manual control…
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Message Edited by Ben on 05-03-2006 12:27 PM
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PID VI - Output Range Question

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