Soil temperature sensor

[yalew]

Could anyone recommend me a reasonable soil temperature sensor, thermistor, thermicouple? I want to measure soil temperatures...
Thanks in advance

 

[jimkirk]

Some details would help. Accuracy, resolution, rate of readings, number of sensors, environmental concerns, et cetera.

Basically, just about any thermal sensor could work. The housing of it is probably more crucial. I'd take a look at

http://www.omega.com/.

They have scads of sensors in all sorts of housings, data loggers, et cetera.

Personally, I have an Oregon Scientific indoor/outdoor thermometer with sensors around my house and yard that communicate via RF to a central unit. One of the sensors has a thermistor in a housing on a cable that can be buried in the ground.

 

[TurboXS]

As jimkirk says.............details

http://www.jaycar.com.au/productVie...d2=&pageNumber=&priceMin=&priceMax=&SUBCATID=

 

[yalew]

Thanks for your replys! Some detail about the measurement
Accuracy - within +/-1 degree centigrade
Rate of reading once a day
Number of sensors - for the trial one (after verification much more)
....
I want to measure the soil temperature say at a depth of 1 m everyday with an accuracy of 1 deg. centig.

 

[itsmoked]

Are these in a fixed location? Dig a hole, drop it in, and leave them?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[cbarn24050]

Hi, PT100 sensors are the best at htis temp range.

 

[jimkirk]

How do you plan to ultimately collect the data? That could be a bigger issue than just having probes in the ground, depending on what you want to do...a few dozen probes in a field versus thousands of probes scattered over hundreds of miles, just as an example. Manual readings versus automated readings.

 

[yalew]

Thanks for the replys.
The temperature measuring points are in a fixed location. For the time being I want to have it in a manual reading manner.

 

[yalew]

Can LM35 sensors be used for soil temperature?

 

[itsmoked]

Absolutely. They would work fine.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[ScottyUK]

You will need to encapsulate them in some sort of protection from the environment - soil is usually wet, more-or-less conductive, and frequently corrosive to metals. None of those conditions are especially good for electronic components. If there won't be any mechanical threat to the sensors, adhesive-lined heatshrink could be a good choice.


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Sometimes I only open my mouth to swap feet...

 

[itsmoked]

I second that!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[yalew]

Thank you so much for the replys. What is the best way to protect them (encapsulate) this sensors? or are there other encapsulated alternatives?

 

[richs]

Good morning-

Shoot, almost anything can be used. I would suggest
PVC sprinker pipe, and/or schedule 125. There are
threaded pipe adaptors with end caps that can be easily
used for this purpose. The circuit board in question is
placed inside the pipe, one end of the the pipe is glue
capped, the other with the treaded adaptor. The wires
through the treaded end cap with silicon water barrier.
Screw the whole thing together and stuff it in the
ground! There might be a time lag between the surrounding
soil and the temperature probe, but not much. Any
temperature rise between the existing electronics and
the outside soil should be negliglable, however, if not,
then the probe outside the pipe.

A quick trip to the hardware store and a tad bit of work
with a drill press or hand drill and you are ready to
rock and roll. Or, perhaps soil and roll?

Cheers,

Rich S.

 

[ScottyUK]

I have successfully encapsulated sensors in cable glands before. They provide a sound mechanical anchor to the cable and the sensing element can be potted in resin quite simply once the cable is mounted. The cable is chosen for mechanical strength rather than current and voltage rating - rubber insulated cable primarily for portable power tools is ideal for applications where a tough flexible cable is needed.

The method works well with both metal and plastic glands - for a temperature sensing element a metal (stainless steel) gland would be a good choice with the sensor being potted in a polyester resin. Epoxy would work too, but the low viscosity of polyesters is usually easier to deal with than most epoxies from a practical point of view. Both materials are essentially inert chemically (or you have some really nasty soil conditions!).

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Sometimes I only open my mouth to swap feet...