The Adcon SM1 Soil Moisture Sensor

Thursday, 01 July 2010 00:00

The new Adcon SM1 Soil Moisture Sensor is a multilevel capacitance probe, which is available in many different lengths. Its outstandingly low power consumption allows several sensors to be connected to the same RTU, with which it is communicating via the standardized SDI-12 protocol. What makes the probe even more interesting is its excellent price-performance ratio.

Sensor versions and details

Basically an SM1 probe consists of three components: the access tube, the interface board and one or several sensor boards. To the currently available 30cm sensor board we will soon add a 50cm version. Since up to three sensor boards can be connected to each other this will allow us to build almost any length probe from 30 to 150cm.

This picture shows the 30cm version. While an O-ring seals the top cap the cable is fed through a solid metal cable gland, also providing IP-67 protection. By default 5 meters of cable are provided, featuring the Adcon standard 7-pin male Binder connector.

A common feature of all SM1 versions is the fact that there is always one soil moisture sensor every ten centimeters, while every sensor board also holds one temperature sensor. That means that for example a 60cm probe, consisting of 2 sensor boards with 30cm each, offers 6 soil moisture and 2 soil temperature sensors. Soil temperature sensors are placed at the center of a board, at15cm on the 20cm boards, and at 25cm on the 50cm boards. The above mentioned 60cm sensor therefore has two temperature sensors at 15 and 45cm.

Combi-Pack with A755 GPRS

Wherever a stand-alone soil moisture sensor needs to be installed - outside the coverage of an Adcon UHF radio network - the A755 GPRS is the ideal RTU.

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Featuring an SDI-12 port which accepts up to 40 SDI-12 values, and a large 3,1Ah NiMH battery pack, charged by a 460mA solar panel, the A755 easily supports up to 4 SM1 soil moisture sensors.

Furthermore a rain gauge or a water meter can be connected, since the A755 also provides an integrated pulse input.

Pricewise the two make a very attractive bundle!

Combi-Pack with A723 addIT

Since the introduction of the Series 4 RTUs even the little 10mW satellite, the A723 addIT, features an on-board SDI-12 adapter. Like its bigger brothers A753 and A755 the SDI-12 interface of the A723 Series 4 addIT supports up to 40 SDI-12 values.

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Given the low price of this RTU this makes an ideal combination with the SM1 sensor, a perfect soil moisture station to be integrated within any Adcon UHF network.

It also allows an irrigation gauge and/or an irrigation meter to be hooked up and transmitted at the same time.

Together with its many other analog and pulse inputs it provides the A723 addIT with the capability to become a fully grown monitoring station which not only measures soil moisture, but can also hold all the sensors required to calculate evapotranspiration.