A two-phase audio-frequency oscillator

1934 ◽  
Vol 74 (448) ◽  
pp. 365-371 ◽  
Author(s):  
D.P.M. Millar
1938 ◽  
Vol 15 (10) ◽  
pp. 347-348 ◽  
Author(s):  
Muirhead and Co., Ltd.

1937 ◽  
Vol 5 (5) ◽  
pp. 230-231
Author(s):  
Sanford C. Gladden

1975 ◽  
Vol 18 (4) ◽  
pp. 612-614
Author(s):  
B. A. Kuznetsov ◽  
V. F. Sen'ko

1980 ◽  
Vol 239 (4) ◽  
pp. H570-H570
Author(s):  
Billy J. Barber ◽  
E. W. Quillen Jr. ◽  
Allen W. Cowley Jr.

An inexpensive telemetry system using transducers and recorders commonly available, i.e., Statham and Grass, is described. The direct-current signal of a Statham transducer is applied to a voltage-controlled oscillator, thereby frequency encoding the pressure sensed by the transducer. This encoded signal frequency modulates a Colpitts oscillator, which acts as a radio-frequency oscillator-transmitter in the 88- to 108-MHz band. This transmitter and transducer, along with a rechargeable NiCd battery pack (total wt 0.5 kg), are mounted in a canvas jacket and worn by a dog previously prepared with a chronic indwelling arterial catheter. With a fully charged battery pack, a signal can be transmitted up to 250 ft for 50 h. A frequency-modulation automotive receiver, powered by and interfaced with a Grass 7B recorder, receives the signal and drives a tachometer circuit that reconverts the audio-frequency signal to a voltage proportional to pressure. This voltage is then applied to the driver amplifier of the Grass to produce a charted record. This system introduces no distortion as seen by comparison of direct and telemetered signals and is drift free for intervals exceeding 24 h.


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