Pressure sensor, transmitter, and tire condition monitoring apparatus

A tire condition monitoring apparatus has a pressure sensor that measures air pressure in a tire of a vehicle. The apparatus also has a transmitter that transmits pressure data measured by the pressure sensor, and a receiver that receives and processes data transmitted by the transmitter. The pressure sensor has a diaphragm (103) exposed to air of the tire, and metallic material (101) covering the diaphragm. The transmitter has a power supply circuit (33,35) and a connecting member (300, 400). The power supply circuit (33, 35) supplies electricity for activating the transmitter. The connecting member (300, 400) connects the power supply circuit (33, 35) with the metallic material (101) such that the potential of the metallic material (101) is the same as the potential of the power supply circuit (33, 35).