PC Audio Power Meter
Approx construction cost US$43
An interface for use with your PC that allows you to measure the power output from audio amplifiers.
This project is the latest in the occasional series of PC-based test equipment. Previous units were based on circuits from our “Interface” series of articles. This device is based on an analogue-to digital converter (ADC) featured in the series, but it is otherwise original. It enables a PC to measure power, and it is primarily intended for use with audio power amplifiers. However, the interface uses d.c. coupling and it could probably be modified for use in some d.c. power measuring applications.
When used for audio power measurement it provides an 8 ohm dummy load, and shows the peak power and voltage delivered to the load. It also has a virtual panel meter that shows the r.m.s. power level when using sinewave test signals.
The circuit connects to the printer port of the host PC, and the port does not need to be a bidirectional type. The power meter program is written in Visual Basic 6, and it requires Windows 95, 98 or ME to run. Note that it will not work with other versions of Windows. Visual Basic 6 produces programs that are incompatible with 16-bit versions of Windows such as version 3.1. Windows NT and 2000 do not permit the form of direct port access, which is essential to the operation of this software.
More details on this construction project can be found in the February 2001 issue of EPE Online, the world's first web-delivered electronics and computing hobbyist magazine.
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