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Electronics => Beginners => Topic started by: asg32000 on January 19, 2016, 03:03:07 am

Title: Units of X/Y/Z
Post by: asg32000 on January 19, 2016, 03:03:07 am

I am working with a pressure sensor that has a "Sensitivity" rating with units of ?V/V/mmHg.  I believe ?V is the output voltage, V is the excitation voltage (for the wheatstone bridge), and of course mmHg is the pressure you are sensing.  My question is: when trying to calculate the expected ?V output, would I do something like this?

(?V/V/mmHg sensitivity rating)/(excitation votage V * pressure in mmHg)

You can't just do standard "order of operations" to calculate this, right? e.g. X divided by Y, then divide that by Z?  X/(Y/Z)...?

Any help would be appreciated.

Title: Re: Units of X/Y/Z
Post by: rich on January 19, 2016, 03:52:22 am

Vout = Sensitivity * Vexcite * pressure

Think of as if you increase any of the 3 variables, you would expect the voltage to increase.

Or use the units as a clue to get:

Sensitivity = Vout / Vexcite / pressure

and rearrange with algebra from there:

Sensitivity = Vout / (Vexcite * pressure)
Sensitivity * (Vexcite * pressure) = Vout

Title: Re: Units of X/Y/Z
Post by: asg32000 on January 19, 2016, 01:44:37 pm

Thanks!  That shouldn't have been so hard...  Somehow I forgot to think about it algebraically.  I appreciate it.