Flow calibrator

A gas flowmeter comprising in combination:

• an enclosure;
• a piston movable within said enclosure, the piston having a surface which forms a clearance seal with a surface of said enclosure;
• a channel for receiving a gas flow to be measured and directing said flow so as to move said piston within said enclosure;
• and
• a movement detector for detecting movement of said piston and generating therefrom electrical signals representative of said gas flow to be measured;
• wherein said piston and enclosure have respective interfacing portions which have substantially the same coefficient of thermal expansion;
• wherein said piston contains carbon lubricating material to reduce friction in the event of contact with said enclosure;
• wherein said interfacing portion of said piston contains graphite and said interfacing portion of said enclosure contains borosilicate glass.

A method of measuring gas flow, comprising the step of:

• providing an enclosure and a piston movable within said enclosure, the piston having a surface which forms a clearance seal with a surface of said enclosure, said piston and enclosure having respective interfacing portions with substantially the same coefficient of thermal expansion;
• channeling a received gas flow to be measure, and directing said flow so as to move said piston within said enclosure;
• and
• detecting movement of said piston and generating therefrom electrical signals representative of said gas flow to be measured;
• further comprising the step of making said portion of said piston containing graphite and making said portion of said enclosure containing borosilicate glass.

A gas flowmeter comprising in combination:

• an enclosure;
• a piston movable within said enclosure, the piston having a surface which forms a clearance seal with a surface of said enclosure;
• a channel for receiving a gas flow to be measured and directing said flow so as to move said piston within said enclosure;
• and
• a movement detector for detecting movement of said piston and generating therefrom electrical signals representative of said gas flow to be measured;
• wherein said piston and enclosure have respective interfacing portions which have substantially the same coefficient of thermal expansion;
• wherein one of said portions contains carbon and the other of said portions contains glass.

A method of measuring gas flow, comprising the steps of:

• providing an enclosure and a piston movable within said enclosure, the piston having a surface which forms a clearance seal with a surface of said enclosure, said piston and enclosure having respective interfacing portions with substantially the same coefficient of thermal expansion;
• channeling a received gas flow to be measured, and directing said flow so as to move said piston within said enclosure;
• detecting movement of said piston and generating therefrom electrical signals representative of said gas flow to be measured;
• and
• making one of said portions containing carbon and the other of said portions containing glass.

A method of measuring gas flow, comprising the steps of:

• providing an enclosure and a piston movable within said enclosure, the piston having a surface which forms a clearance seal with a surface of said enclosure, said piston and enclosure having respective interfacing portions with substantially the same coefficient of thermal expansion:
• channeling a received gas flow to be measured, and directing said flow so as to move said piston within said enclosure;
• detecting movement of said piston and generating therefrom electrical signals representative of said gas flow to be measured;
• providing said piston with carbon lubricating material to reduce friction in the event of contact with said enclosure;
• and
• making said interfacing portion of said piston containing graphite and said interfacing portion of said enclosure containing borosilicate glass.