# What is the negative pressure?

I have vacuum pump connected to quartz tube and vacuum sensor, when the pump reaches it max value the sensor reading (-1 bar) and the analog gauge in the pump reach the max value which is (-1000mbar). what is meant by negative pressure? I know it is below ATM but I need to translate it to positive value, example my experiment I want to reach for example 0.05 mbar does the señor and pump help me or not? can any one explain that to me please?

• It seems like looking up the difference between Gauge Pressure and Absolute Pressure is exactly what you need. Dec 19, 2021 at 0:55

what is meant by negative pressure?

A pressure that is below zero gauge pressure, i.e, below 1 atm.

To translate it into a positive value, you need to use units of absolute pressure. In general those are Pascals (Pa) or Torr. 1 atm equals an absolute pressure of about +101.325 kPa or +760 Torrs

So 0.05 mbar equals an absolute pressure of about + 5Pa or +0.038 Torr. A gauge pressure of -1 bar is an absolute pressure of 0 Pa, or a theoretical perfect vacuum, which doesn’t exist, even in outer space.

The following link describes various pressure gauges used for measuring absolute (positive) near vacuum conditions that you might find interesting.