Gas meter is a device for measuring the volume of gas used. The type of gas meter commonly used at homes consists of a tight metal box divided through the center into two separate chambers, or bellows. Each chamber has a movable partition that divides it into two parts, making four separate chambers in all. The gas is measured by first filling and then emptying each of these four chambers, and automatically registering the number of times each chamber is filled and emptied. While one chamber is being filled another is being emptied, so that the consumer receives an even flow of gas at all times.
The upper part of the meter contains the mechanism for registering the movement of the various chambers in cubic feet or cubic meters and showing the volume on a set of dials. Gas meters register volumes of gas accurately. State authorities permit their legal use as measuring devices for periods as long as 21 years before requiring rechecking of the meter.
