{"id":20,"date":"2011-03-27T21:59:00","date_gmt":"2011-03-27T21:59:00","guid":{"rendered":"http:\/\/cazenave.co.uk\/wp\/?p=20"},"modified":"2014-04-30T17:12:33","modified_gmt":"2014-04-30T17:12:33","slug":"temperature-monitoring-with-temper","status":"publish","type":"post","link":"https:\/\/cazenave.co.uk\/temperature-monitoring-with-temper\/","title":{"rendered":"Temperature Monitoring with TEMPer"},"content":{"rendered":"

I got a USB thermometer from eBay called TEMPer. I found some code which creates a driver and reporting app for which, with some patching, I used in a little cronjob. The code can be found at SlackBuilds.org<\/a>, and seems to work OK on Slackware 13.1. It does, however, output temperatures which are generally 9.3\u00a0Celsius\u00a0higher than the actual temperature, so the figure below has erroneously high temperatures.<\/p>\n

Below is a plot of last month’s temperature data from the TEMPer.<\/p>\n

\"octave_analysis\"<\/a>
Raw (blue) and filtered (green) temperature (Celcius)<\/figcaption><\/figure>\n

I wrote a little Octave\/MATLAB script which takes the raw data from the cronjob output and does a frequency analysis with the FFT tools in Octave\/MATLAB. I use the frequency domain to lowpass filter the raw data (the blue line) with a cutoff at 1\/7 per day to smooth the data (the green line). Comparison of this filtered line with some regional data from a\u00a0meteorological\u00a0station shows pretty good agreement:<\/p>\n

\"monthtodate\"<\/a>
Meteorological data from http:\/\/www.southamptonweather.co.uk\/wxgraphs.php for the same time period as the graph above.<\/figcaption><\/figure>\n\n\n\n\n
<\/td>\n<\/tr>\n
Meteorological data from\u00a0http:\/\/www.southamptonweather.co.uk\/wxgraphs.php for the same time period as the graph above.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
<\/div>\n

The line of interest is the green line in the lowest panel. The duration of the two plots is the same, but the y-axes differ in scaling.<\/p>\n

There are a number of interesting trends in the two data sets. Both graphs decrease for the first 5 or 6 days followed by a relatively slow increase in temperature which peaks at ~12 days before present (the 15th). From the 15th onwards, temperatures decrease until the 17-18th, where the temperature begins to rise again, until the 22nd, where the graphs diverge. The meteorological data continue on their upward trend, however the TEMPer data suddenly drop 2-3 Celcius.<\/p>\n

The reason for this divergence is we turned our heating off around the 21st. Following this static shift of a few degrees, the two graphs track the same trend, but the TEMPer data is now lower.<\/p>\n

Finally, the huge temperature spike in the TEMPer data for the last two days or so is from friends visiting and the heating being put back on for two late nights.<\/p>\n

I’ve got a longer time series from the internal sensors on the PC, but hopefully this USB thermometer will give me less CPU-load-dependent temperatures.<\/p>\n","protected":false},"excerpt":{"rendered":"

I got a USB thermometer from eBay called TEMPer. I found some code which creates a driver and reporting app for which, with some patching, I used in a little cronjob. The code can be found at SlackBuilds.org, and seems to work OK on Slackware 13.1. It does, however, output temperatures which are generally 9.3\u00a0Celsius\u00a0higher […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[53,51,50,49,52],"tags":[],"_links":{"self":[{"href":"https:\/\/cazenave.co.uk\/wp-json\/wp\/v2\/posts\/20"}],"collection":[{"href":"https:\/\/cazenave.co.uk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cazenave.co.uk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cazenave.co.uk\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/cazenave.co.uk\/wp-json\/wp\/v2\/comments?post=20"}],"version-history":[{"count":3,"href":"https:\/\/cazenave.co.uk\/wp-json\/wp\/v2\/posts\/20\/revisions"}],"predecessor-version":[{"id":47,"href":"https:\/\/cazenave.co.uk\/wp-json\/wp\/v2\/posts\/20\/revisions\/47"}],"wp:attachment":[{"href":"https:\/\/cazenave.co.uk\/wp-json\/wp\/v2\/media?parent=20"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cazenave.co.uk\/wp-json\/wp\/v2\/categories?post=20"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cazenave.co.uk\/wp-json\/wp\/v2\/tags?post=20"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}