Wide range vacuum gauge

A device for determining a pressure of a gas in an evacuated chamber comprising:

• a first cylinder positioned in fluid communication with the evacuated chamber, said first cylinder forming a first compressed gas chamber;
• a first reciprocating piston received within said first cylinder and mounted for reciprocal movement within said cylinder;
• a second cylinder formed in said first piston;
• a second reciprocating piston received within said second cylinder and mounted for reciprocal movement within said cylinder;
• a communication means for selectively fluidly communicating said compressed gas chamber with the evacuated chamber;
• a drive means for reciprocating each of said first and second pistons between retracted positions and extended positions;
• a determining means for determining when a predetermined pressure differential between said compressed gas chamber and the evacuated chamber is reached;
• a processing means for determining the pressure of the gas within the evacuated chamber based on the predetermined pressure differential and when said predetermined pressure differential is reached.

A method for determining a pressure of gas in an evacuated chamber comprising:

• providing a cylinder and piston assembly, said cylinder forming a compressed gas chamber selectively communicating with the evacuated chamber;
• positioning said piston in a retracted position where said compressed gas chamber and the evacuation chamber are in fluid communication with one another;
• advancing said piston in said cylinder to an extended position, the extended position being that position where a predetermined pressure differential between gas in said compressed gas chamber and the gas in the evacuated chamber is reached;
• determining the position of said piston to reach the extended position;
• and
• determining the pressure of the gas in the evacuated chamber based on said predetermined pressure differential and said position of said piston.

A method for determining a pressure of a gas in an evacuated chamber comprising the steps of:

• compressing a gas of a known volume in a cylinder, said compressing carried out by a solid piston reciprocably received in said cylinder;
• determining a pressure differential wherein said pressure differential is the difference between the pressure in the evacuated chamber and the cylinder;
• determining a compression ratio of the gas within said cylinder;
• and
• determining the pressure of the gas in said evacuated chamber based on said pressure differential and said compression ratio.