On the other hand, nearly all vacuum equipment I have worked with reads pressure in torr, millitorr, and (occasionally) "microns," as in micrometers or mercury. I have not seen pascals used for vacuum systems.
The unit "mmHg" does not lend itself to precision pressure measurements, since
- Mercury density changes with temperature
- Mercury density changes with pressure
- Gravity varies with geographic location
This second consideration makes mmHg especially bad, since the size of the unit changes with the size of what you are trying to measure!
John
Pierre Abbat wrote:
A couple of pseudometric units in common use are the calorie (used for measuring food energy) and the torr (used for measuring blood pressure). I know some countries put kilojoules on nutrition labels, but is there any movement to unseat the torr?
phma
