[Sean Marconette]

Just a question, is the isolator gauge open to atmosphere after it is filled? If it is closed does anyone notice a difference in the gauge reading when it's hot or cold?

The reason I ask these questions is, if the gauge is sealed to atmosphere temperature fluctuations will impact its reading. You may not notice this if it does not start at 0 on the gauge. I used to use a glycerin filled 0-15 PSI gauge for my tire pressure. I always had to open the vent port to zero the gauge each time it was used if the temperature had changed. I finally dumped the glycerin. This is just an example of a fluid in a sealed vessel, unless they are pressure compensated they may not be as accurate as you may think.

At least with an electric sensor and gauge, as long as the span of the sensor and gauge are the same it will give consistent readings.
Something to think about.

Sean