| 摘要 |
A device for measuring the repiratory capacity of a baby comprises a transmitter (10) allocated to the person which comprises an r.f. oscillator (11) generating a carrier signal, in the frequency-determining branch (12) of which there is a sensor capacitor (13) which is arranged on the person's body in such a way that its capacitance changes depending on the respiratory capacity and the transmitter transmits a carrier signal frequency-modulated in accordance with said capacity. The signal is received via an aerial by a receiver and further processed therein in such a way as to provide a preferably low-frequency signal characteristic of the person's respiratory capacity. Here, the transmitter (10) also amplitude-modulates the r.f. signal in accordance with the persons respiratory capacity. The received signal is mixed in the receiver with a further r.f. signal, the frequency of which is higher thatn that of the carrier signal, thus improving interference immunity. The reception aerial is a wide-band type with a tuned oscillation circuit so that it cannot be adversely detuned by different people. |
