This post is about producing a low cost DIY energy logger for residential or business applications using split core current clamps and off the shelf analogue data loggers. There is discussion of suitable components to build this system. The software should be fairly straightforward and is left to the system designer.
Split core current clamps are great for monitoring current consumption in a building as the are easily connected around a mains cable.
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For domestic applications a mini-hinged 80A current clamp will easily monitor power consumption up to 18 kilo watts. In business applications, when monitoring the three phases, 3 current clamps rated at 150 Amps will cope with total power consumption of upto 100 kilo watts per distribution board.
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If required, the mini current clamps can be used to monitor individual circuits as they are small enough to fit a number of them inside the distribution board.
These current clamps produce an AC voltage that is proportional to the current upto a maximum of 0.33 V AC when the rated current is flowing. So for example, when a current of 20 Amps is flowing through an 80 Amp device, they produce a voltage which is a quarter of 0.33 V which is 0.33/4 = 82 milli volts.
A simple op amp with some gain followed by an active rectifier will give a DC voltage which is proportional to the AC voltage. A circuit for doing this will be presented on the next post including information on how to calibrate them.
Finally, this analogue DC voltage can be logged using any of these devices.
http://www.picotech.com/multi-channel-daq.html