what is the difference between jacket pressure gauge and chamber pressure gauge of the autoclave???

Many of us think pressure gauges for indicating pressure in the jacket and chamber of an autoclave are same. In case of Fully automatic autoclave with pulse vacuum system, it consists of jacket and chamber. Firstly the steam is stored in the jacket formed in the steam generator and after the process is to be forwarded the steam from the jacket is sent to the chamber for heating and sterilizing process.

To measure the required pressure there are 2 different types of pressure gauges, one for indicating jacket pressure and other type for indicating pressure in chamber. The pressure gauge that is used to measure pressure of jacket is the normal pressure gauge that starts from Zero but the pressure gauge which is used to measure pressure of chamber starts from negative i.e it indicates below Zero. As we can see the differences from the picture below that I have taken from One of the autoclave in a hospital.

The pressure Indicator of  the chamber pressure is also known as compound gauge which measures above and below (vacuum) atmospheric pressure.As the chamber needs to be vacuumed for several times before heating and feeding steam for better sterilization (also known as pulse vacuum type autoclave) the pressure in the chamber falls below zero, during this procedure autoclave has to sense the decrease in pressure and for that it needs compound pressure gauge.

Fig1A. Pressure Gauge For Indicating Jacket pressure

Fig1B. Pressure Gauge For Indicating Chamber Pressure