This is my first time using SCP and I want to make sure I correctly understand the values used. I'm using a ML1100.

I have a pressure transducer that ranges from -15psi to 15psi. I'm using it to check vacuum so I'm really looking at 30 in Hg as my low end and 0 (atm) as the top.

My transducer has a 0-10v output. That would seem to me that at 30in Hg of vacuum I would have 0V, open atm I would have 5V, and at a pressure of 15psi I would have 10V.

SCP needs the following values. I'm unsure of a couple here:

Input: This is my analog input on the ML1100.
Input min:
Input max:
Scaled min: -30 ?
Scaled max: 30 ?
Output: I'm using a floating point F location.

Do I just choose some large numbers, 32000 for example to use for my input min/max to get good resolution or am I really missing something here?

Are you using the integrated analog input or an expansion module.
If the onboard analog input, it has only 10 bit resolution ( 0-1023 counts)
15 PSI=30.54 inches of mercury
So see pick below:

Yes, I am using the integrated analog input.

How did you arrive at the 1023 value?

Wouldn't you use a -1023 as the min?

If I were to use my analog expansion card (which I believe is 12 bit), what resolution benefit would I see?

What are the max/min values if I were to use the expansion card?

Thanks for the fast reply!

Page 25 in the pdf may help.

Bob beat me to it but I will post anyway( sence I went to trouble)

To see what different resolutions will get you, raise 2 to the exponent matching the number of bits you have on your A/D converter and divide that into the span of your transducer. Your transducer has a range of -30.54 inHg to +30.54 inHg which gives you a sapn of 61.08 inHg.

(BTW, I don't know if you know this or not, be aware that is is physically impossible to reach 30" Hg of vacuum

Anyways, (61.08 InHg) / (2^10 counts) = .06 InHg/count. This is your resolution: .06 inHg. The ML1100 onboard analog input has a full scale span accuracy of 1%. So your accuracy is 61.06 InHg * 1% = .61 InHg. Find out what your transducer accuracy is and add the two accuracies together an you have the accuracy at which you can read pressure.

Use the same method for the 12 bit expansion module but you need to get the book out and see what the input range actually is. EG, while the full scale for the onboard input on the ML1100 is a 0-10.0 V input, the input range of the 1762-IF4 is -10.5 to 10.5 volts.

For scaling you would use 0-1023. The analog input will return the value (2^N)-1 at full scale where N is the number of bits of resolution you have. 2^10-1 = 1023.

Thank you all for your info. Very helpful.