The Chameleon Wi-Fi sensor array has three sensors connected to a plug. These should be placed at three depths in the soil, normally in the same hole. Typical depths are 20 cm (blue wire), 40 cm (white wire) and 60 cm (red wire). The temperature sensor should be placed at the same depth as the middle (white) sensor. By measuring three depths, you can see how deep the roots are growing during the season. This allows you to match your irrigation to rooting depth. For shallow-rooted vegetable crops, appropriate depths maybe 10, 20 and 40 cm. For deeper rooted crops and trees, installation depths maybe 30, 60 and 90 cm. These depths should be modified based on i) how frequently you irrigate and ii) how deep your soil is.
Chameleon Card sensors are not connected to a plug. They can be placed at three depths in the same hole as described above for the Wi-Fi sensor array. Alternatively, they can be installed at one depth (or two depths) at several different locations. For shallow-rooted crops, sensors may be placed at 20 cm depth at three different locations. For deeper rooted crops, an appropriate depth maybe 30 cm. These depths represent the part of the root zone where most of the water is extracted.
Irrigation systems are designed to give a uniform distribution of water. Each plot in a farm that is controlled by a single valve or tap is called and irrigation bay. In theory, irrigation should be uniform within a bay, and hence you only need to install sensors in one representative location. In reality, irrigation bays are not uniform. For example, flood irrigated fields can be wetter at the top or the bottom of the run than in the middle. In such cases multiple measuring points may be needed. The aim would be to use the sensor information to achieve a more uniform water delivery across an entire irrigation bay.
The first step in saving water is to improve the uniformity of irrigation. It is always worthwhile to do an irrigation uniformity test before installing sensors. Sensors located in dry or wet patches will not be representative of the entire field. This is particularly important for overhead sprinklers and mini-sprinklers. For drip irrigation, sensors should be placed half way between the emitter and the edge of the wetting pattern. Locating the sensors directly under the drip emitter will shorten their lifespan.
The Chameleon is a resistance-type sensor that is calibrated to give the soil water tension or suction. It is different from a 'Gypsum Block' sensor. The Gypsum Block is not sensitive in the 'wetter part' of the soil moisture range (colours blue and green on the Chameleon) and therefore not suitable for monitoring most irrigated crops. The Chameleon sensor is comprised of an inner core of highly absorbent material that releases a lot of water in the 10 to 50 kPa suction range. This material effectively amplifies the soil water signal, so we get high resolution in the part of the soil moisture range most critical for irrigators. This inner core is coated with gypsum to provide buffering of electrical conductivity. The resistance reading is also corrected for changes in soil temperature.
Each soil type has a unique relationship between the soil water content (the amount of water in a given volume of soil) and the soil water suction (the water stress experienced by the plant). If you measure soil water content, there is a different 'number' for which you must irrigate each soil. If you measure soil water suction with a Chameleon sensor, the blue, green and red colours mean the same from the perspective of the plant stress, regardless of soil type. In other words, soil water suction sensors do not need to be calibrated for soil type.
Our aims is as follows: Blue 0-20 kPa (wet), Green 20 to 50 kPa (moist) and Red > 50 kPa (dry).
It is very difficult to make every sensor change exactly at those suction values, and for practical irrigation purposes, it is not necessary either.
Every sensor we build is individually tested to check the colours change in the correct range (that is why your sensor may look 'used').
Each sensor array is colour coded on the package after testing based on the blue to green switch point.
A yellow dot means the colour changed between 20 and 22 kPa.
An orange dot means the colour changed between 18 and 20 kPa.
A purple/pink dot means the colour changed between 22 and 24 kPa.
The expected lifespan of this sensor in the ground is 2 to 4 years, with the shorter time occurring in very wet, acidic or salty soils. The more recent designs are more durable for those who need to dig up and move sensors to other sites. As part of our research, we are modifying the design to increase accuracy and longevity.
The sensors are very dry when packaged for shipment and too dry for the reader to detect them.
When you try and read them straight out of the packet you may see the message on the reader screen "Check connections". This is because the reader can only detect the temperature sensor and not the soil water sensors.
Before you can read the sensors you must soak them in a bucket of water until they turn blue. See the sensor installation instructions here https://via.farm/chameleon-sensor-installation-instructions/
The grey colour indicates the sensor is disconnected.
When a sensor cable is disconnected (open circuit) the reader sees it as a very high resistance. On the Visualisation, anything about 4000 kOhms is assumed to be an open circuit and is colour grey to alert you to the fault. Please check your wiring, particularly at the green terminal block where it may have come loose. You will need the small flat screwdriver supplied with your reader to fix the problem.
Sometimes the soil gets so dry (end of the red zone) that it goes beyond the accuracy of our Chameleon reader. this also shows up as grey on the visualisation and the colour will return when the soil is wetted again.
If you buy Chameleon equipment from our online shop https://viashop.csiro.au/ you will be issued account details and a farm will be created for you within a few days of completing payment.
If you are using Chameleon equipment supplied via an ACIAR funded project then you should have been issued account details.
If you have not received your account details then please contact us via the https://via.farm/contact-us/ page.
Please provide this following and request a login:
You may want to export the sensor data into Excel or another program to analyse the data. You can do this following this method:
The Chameleon Wi-Fi Reader logs sensor data and stores to a memory chip on the Reader before it is uploaded to the via.farm website.
A sensor data record includes a reading from each of the three Chameleon sensors, soil temperature and the sensor array ID. The reader can store up to 1023 sensor data records.
When the reader is left plugged into a sensor array (eg. permanently installed in the field) the reader will automatically log sensor data every two hours and can store 85 days of sensor data. If the reader is left logging for longer than this period the oldest record will be discarded to make space for the most recent.
The Reader does not include a conventional clock. In order to record the time a reading was taken on the website, the reader keeps track of the time since each record was stored (delta time). The delta time value is uploaded with each sensor record and the website converts it to a date and time.
If the reader battery is allowed to go flat with stored data, it will no longer be able to track the delta time. When the stored data is finally uploaded, the measured date will be shifted by the time period the battery was flat.
Key recommendation: Don't allow the battery to go flat while the reader contains stored data.
The actual time data is recorded compared to what is displayed on the website may be off by a few percent (based on the delta time). It is recommended to upload data at least every week in order to minimise this time accuracy issue.
Key Recommendation: Upload logged data frequently (at least every week).
It takes around 3 seconds to upload each record. After each record is uploaded it is removed from the reader. Based on the quality of the Internet connection it will take at least 40 minutes to upload a completely full reader containing 1023 records (85 days).
