Audio Watt Meter
This is an easy trick to measure the output of an amplifier.Here resistor R2 acts as the load for for the amp and it should be able to withstand twice the maximum power of the amp you are going to measure.The meter scale must be calibrated and with a little effort you can get good results.
Audio Watt meter Circuit Diagram with Parts List.
- If 1A bridge is not available , make one with four 1N 4007 Diodes.
- The resistor R2 must be twice the power of amp you are going to measure.
- To calibrate the device, Connect the output of amplifier to to port 1.Also connect a AC voltmeter to port1.
- Set R1 fully off.That means full counter clockwise direction if wired conventionally.
- Adjust the output of amp to read 20Volt rms on voltmeter.This is the equivalent of 50W on 8 Ohm load.
- Adjust R1 for a full scale deflection on meter M1. Now fix the wiper of preset R1 using some super glue.
- Now reduce the voltage across the port 1 by reducing the output power of amplifier under test according to the table given below and mark the readings on the meter scale.The device is ready to measure.