- Voltage, Temperature and Frequency can switching to each others using push buttons.
- Voltage Meter can measure DC voltage between 0v to 50v.
- Frequency Meter can measure frequency up to 65KHz.
- Temperature Meter can use between 00C to 1500C.
- Every functions can paused using push button.
Voltage meter –
Volt meter can measure dc voltages up to 50v. 5V is the maximum voltage can handle PIC microcontroller, as it is voltage divider (10K,1.1K) use for convert 50V to 5V . 5v zener diode use for safety of PIC microcontroller analog input pin.
Temperature meter –
Temperature meter can use between 00C to 1500C. But LM35 sensor can use between -550C to 1500C. Sensor’s resistant is changing opposite to temperature, as it is maximum temperature gives maximum voltage output(5v) and minimum temperature gives minimum voltage output(0v).
Frequency meter –
Theoretically, frequency meter can use up to 65KHz, that is because this circuit made by using Timer 1(16bit) of PIC microcontroller.
Timer 0 can only measure up to 256Hz, that is because timer 0 is 8 bit timer. Transistor part is use for safety of microcontroller from amplitude of wave signal. This circuit can apply 12v amplitude or more changing transistor base resistor value(4.7K). I tested it, using 12v amplitude square wave signal.
If you have problem about accuracy of voltmeter, temperature meter and frequency meter, you can change values (*1,*2,*3)
For more detail: Voltage, Temperature & Frequency Meter With PIC Micro controller