The aneroid is designed to register pressures from 1040 mb to 10 mb or less. The aneroid also serves another function as described below. A pen arm is attached to the aneroid. This baroswitch involves a contact arm connected to the barometer passes over the commutator bar. The contact arm, responding to the pressure changes, moves across the contact points on the commutator bar.
Newer model radiosondes use a capacitive transducer with an aneroid capsule.
The conducting strip transmits humidity and reference information while the insulator strip transmits temperature information. Each fifth contact is a reference contact. Variable modulation is used to transmit the collected information. That is, the radio frequency is changed by the position of the contact arm on the baroswitch. The radio transmitter is located in the pointed plastic cylinder attached to the base of the instrument package.