This voltage to frequency converter is designed to be connected to a frequency counter to display the voltage value being measured.
This converter-counter combination produces a cheap but functionally complete digital voltmeter. The circuit delivers TTL compatible pulses which are 5 µS wide.
The pulse frequency is proportional to the DC voltage being measured. The conversion factor is 10 kHz per volt. When the input level is 0 V the frequency output is 0 Hz.
The resistor R2 (together with C1) determines the conversion factor and has the value of around 90 K. To achieve best results use a metal film resistor for R2 in series with a multiturn
trimmer resistor. This multiturn resistor will enable you to set the correct resistance value. Resistors R9 and R14 must be metal film types.
Calibration:
- Connect the output terminals to the digital frequency counter.
- Set the frequency counter to the appropriate range (ex. 100 Hz).
- Short the input terminals of the converter module together.
- Adjust P1 so that the output frequency is 0 Hz as displayed by the frequency counter (maximum allowable is 2 Hz).
External Wiring Layout
A typical combination to build a functional digital voltmeter using a digital frequency counter as the display module.
Electronic Circuits volume 1.0 - Circuit Nr. 99
The complete data of the electronic circuit described above can be found in the following book and is available from Amazon.com.
Click on the image to view the book.
