09-19-2018, 01:24 PM
Hi Guys
Performing an output power measurement on an amp is simple if you have an oscilloscope and a sine wave generator. You also need bench load, which is just a power resistor of suitable resistance and wattage rating.
Connect the generator to the amp input; connect the load to the output; connect the scope to the output. Set gain or volume to zero.
If the generator has a SYNC output, which can be called a TRIGGER, tie this to the EXT TRIG (external trigger) input of the scope. Set the scope to EXT triggering. This connection will keep the wave displayed on the scope from drifting from side to side.
Turn on the generator, scope and amp. Dial volume up until you see the sine wave get clipped - just a small amount of flattening is all you need to see. Then back off just enough for the peaks to be round again. measure the peak-to-peak voltage then dial volume to zero.
Divide the voltage reading in half for a peak value, then calculate peak power, then divide that by half for continuous power.
Why use the peak-to-peak voltage? It reduces a bit of error reading the value off the scope screen. of course, you might have a scope with built-in metering that can tell you the RMS voltage, in which case you can calculate the continuous power directly.
Performing an output power measurement on an amp is simple if you have an oscilloscope and a sine wave generator. You also need bench load, which is just a power resistor of suitable resistance and wattage rating.
Connect the generator to the amp input; connect the load to the output; connect the scope to the output. Set gain or volume to zero.
If the generator has a SYNC output, which can be called a TRIGGER, tie this to the EXT TRIG (external trigger) input of the scope. Set the scope to EXT triggering. This connection will keep the wave displayed on the scope from drifting from side to side.
Turn on the generator, scope and amp. Dial volume up until you see the sine wave get clipped - just a small amount of flattening is all you need to see. Then back off just enough for the peaks to be round again. measure the peak-to-peak voltage then dial volume to zero.
Divide the voltage reading in half for a peak value, then calculate peak power, then divide that by half for continuous power.
Why use the peak-to-peak voltage? It reduces a bit of error reading the value off the scope screen. of course, you might have a scope with built-in metering that can tell you the RMS voltage, in which case you can calculate the continuous power directly.