Log data from Watts Up? power meter
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This is a simple Python utility for logging data from a Watts Up? Pro power meter. Documentation for the serial port interface for the meter is available in this PDF file.

Other software capable of logging data on the Watts Up? meter are available for download from watts up?, and they sell a realtime version for Windows for $72.95. One example I found of reading from the Watts Up? Pro in Python was this script.

The program will by default assume the most common device name for Linux and OS X platforms, but the serial port device can also be specified with the command line option -p.

The Watts Up? Pro uses an FTDI serial to USB adapter internally. If the driver is not already installed on your operating system, download the latest driver from the FTDI website.


Basic usage from the command line:

To log realtime data at the default sample rate (1 s) to the file sample.log, use

wattsup.py -l -o sample.log

A basic realtime plot can be added to the above with

wattsup.py -l -g -o sample.log

(requires numpy and matplotlib).

Full description of options will be given by

wattsup -h


Program to log, display data to console, and generate a simple real time plot
Simple plotting program for files already logged.
Experimental TraitsUI interface to power meter logging (only does simulated logging for now)

In the samples subdirectory, there are several raw data logs that can be used as sample input with the --simulation-mode option. Note that they may not be interesting to watch in real time. These files log the data as it comes from the serial port, with the --raw option.

Sample data from a small window air conditioner
Sample data from a two-motor, 3-speed fan
Charging an iPhone 3gs
Charging an iPhone 4


  • Fetching data from internal storage is not yet working
  • Plotting is currently very rudimentary. Some things to add include:
    • Better autoranging
    • Options for plotting power, current, or both
    • Cumulative display or plot of energy used


These programs are free software: you can redistribute them and/or modify them under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. A copy of the GPL version 3 license can be found in the file COPYING or at http://www.gnu.org/licenses.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.