Perl uses a multimeter to report power consumption

ELECTRICKERY

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Today’s digital multimeters can do more than measure current and voltage. Multimeters also measure capacity and temperature. An inexpensive multimeter can talk to your PC via the serial port, and simple Perl scripts let you read and visualize data in neat charts.

I was browsing a mail order catalog for electronics the other day when I noticed a couple of low-budget, digital multimeters with RS 232 interface. I discovered the MAS-345 model by Mastech on eBay for US$ 35 and quickly pressed the “buy-it-now” button.
When the device arrived, it came with just a Windows CD. After a quick search on the web, I discovered the Marsh project, which uses a bit of C code to address the Mastech MAS-345 among other multimeters.