I've resurrected my old spreadsheet to log my grid and solar usage in the office now that I have both meters wired in and recording use and production.
Another thought crossed my mind last night. The two sensors used to trigger the differential thermostat to control the heating pump are nicely calibrated to provide 10mV per Kelvin, or degree Centigrade. At freezing point, they output 2.73v which represents 273K. 100 Centrigrade later, they give out 3.73v, so the entire range between 0 and 100 Centigrade is nicely within the limits of the pair of AtoD converters on my Velleman USB interface boards. So, by wiring in the interface to the sensor lines on the differential thermostat I can interrogate the voltage produced by each of the sensors, run a little simple maths and use the laptop to display the absolute and differential temperatures in degrees C.
Today around 1pm (the hottest day of the year thus far) and the sun just off the axis of the thermal panel, I recorded a temperature of about 68C on the panel and 64C on the return line from the calorifier.
What I need to do now is to create a data-logger that will allow me to record temperatures, and hence performance, over a longer period of time. A few days would be good...a few weeks even better, and graphical output would be very nice indeed. So, there's my next software project!
'twas bloomin hot today...not sure how hot but the van was hot. Hotter outside though. And, as I pulled out tonight, my min-max indoor/outdoor temperature/humidity gauge arrived in the post!
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