A voltage to frequency converter with a control range of 1:1000 can be easily constructed by using the IC TSC9402. The given component values in the circuit produces a conversion
factor of 1kHz/1V. The input voltages from 10 mV up to 10 V are converted to frequencies 10 Hz up to 10 kHz.
This conversion can be changed if desired through the potentiometer P1.
The circuit has two outputs: a sharp pulse comes out from pin 8 with the main output frequency. A clean squarewave comes out of pin 10 but its frequency is half
of the output frequency at pin 8. Calibration: use an accurate frequency counter and adjust P1 so that an input level of 10 mV will produce a signal of 10 Hz at the output.
One area of application for this circuit is the telemetry. In this case, telemetry of voltage values. By converting the voltage value to a frequency,
the value can be transmitted either via a coaxial cable or radio. Wireless telemetry method using radio, can be realized by using the output of this circuit to
modulate the carrier signal of a transmitter. It is not possible to use directly the output frequency of this circuit since it produces only a maximum of 10 kHz (equivalent to
a measured voltage of 10 volts at its input).
The modulation technique can be any of the available industry standard modulations. It can be AM, FM, SSB, FSK, etc.
The following diagram shows how to use the circuit for remote measurements using a coaxial cable. The technique is limited to several meters though.
The distance can be increased by using a signal amplifier.
The diagram on the right shows the circuit modulating a transmitter to transport the measured value via radio signals. This technique allows remote telemetry over very long distances.
If the signal is repeated via a satellite transponder, the telemetry can be done worldwide.
Parts Placement Layout
External Wiring Layout
Electronic Circuits volume 1.0 - Circuit Nr. 20
The complete data of the electronic circuit described above can be found in the following book and is available from Amazon.com.
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