Pirani gauge



  • A pressure gauge utilizing a hot wire placed in the gas whose pressure is to be measured. The rate of heat loss of the wire, which is connected to a bridge, depends on the rate at which the gas conducts heat away from said wire. The voltage across the wire is maintained constant, and since its resistance varies proportionally to its temperature, changes in resistance enable the measurement of the surrounding pressure. Conversely, the resistance of the wire can be held constant, so that the potential difference across it corresponds to the pressure. Utilized to measure low gas pressures.