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Make your own grass minimum thermometer

Traditional grass minimum thermometers are expensive. And delicate. Over the years I’ve lost a few of these spirit-filled devices thanks to curious foxes and other wildlife.

But using a £20 datalogger off eBay – units that are used for cold chain supply – and junk found in the garden I’ve found a solution.

As well as the logger and probe you’ll need:
Access to a PC
An old pickle jar with lid, preferably with a wide neck.
1.6m garden cane, cut into 8x 20cm lengths.
Thin garden wire.

list

Once you decide where to place the device (a part of lawn with limited traffic) dig a hole deep enough so just the very top is exposed.

Drill a small hole (big enough for the wire to pass through and the probe to fit snugly) into the top 2cm of each cane before carefully hammering each length into the surrounding turf, leaving 10cm exposed. The last length- that will host the probe – should go in the centre.

Drill a small hole in the lid that is just big enough for the probe to pass through.

You are now ready to place the datalogger into the jar to start recording.

done

First you’ll need to set up the device on your PC. Programs to do this are available to download.

The devices can hold up to 16,000 records. I set mine to 1 minute intervals, allowing for a continuous 11 days of records.

The enclosure is more to stop any foot traffic kicking over and damaging the probe. If wildlife proves to be a problem there is an option of running a very-wide gauge grill over the top.