Paper: Effective Calibration of Low-Cost Soil Water Content Sensors

Interesting article about calibrating sensors:

Effective Calibration of Low-Cost Soil Water Content Sensors

Heye Reemt Bogena * , Johan Alexander Huisman, Bernd Schilling, Ansgar Weuthen and Harry Vereecken Institute of Bio- and Geosciences, Agrosphere Institute (IBG-3), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany * Author to whom correspondence should be addressed.

Academic Editor: Gonzalo Pajares Martinsanz

Received: 27 November 2016 / Revised: 12 January 2017 / Accepted: 16 January 2017 / Published: 21 January 2017

Abstract Soil water content is a key variable for understanding and modelling ecohydrological processes. Low-cost electromagnetic sensors are increasingly being used to characterize the spatio-temporal dynamics of soil water content, despite the reduced accuracy of such sensors as compared to reference electromagnetic soil water content sensing methods such as time domain reflectometry. Here, we present an effective calibration method to improve the measurement accuracy of low-cost soil water content sensors taking the recently developed SMT100 sensor (Truebner GmbH, Neustadt, Germany) as an example. We calibrated the sensor output of more than 700 SMT100 sensors to permittivity using a standard procedure based on five reference media with a known apparent dielectric permittivity (1 < Ka < 34.8). Our results showed that a sensor-specific calibration improved the accuracy of the calibration compared to single “universal” calibration. The associated additional effort in calibrating each sensor individually is relaxed by a dedicated calibration setup that enables the calibration of large numbers of sensors in limited time while minimizing errors in the calibration process. View Full-Text

Keywords: soil water content; permittivity; calibration; sensor-to-sensor variability; SMT100 sensor

This article is available here: http://www.mdpi.com/1424-8220/17/1/208

Thanks!

zoomx: Thanks!

Say thanks to the Authors and cite them! ;)

Indeed a very interesting paper and a surprise for me since I am the developer of the SMT100 sensor. We do have an RS485 version as well and I am just playing a little bit with an Arduino, an RS485 shield and the RS485 version of the SMT100.

ChrisRF: Indeed a very interesting paper and a surprise for me since I am the developer of the SMT100 sensor. We do have an RS485 version as well and I am just playing a little bit with an Arduino, an RS485 shield and the RS485 version of the SMT100.

I'm a Associated Researcher working on a Laboratory for Climate Observation, this Lab belongs to a small Center for Technological Development and Engineering in my University; our main research line is developing low cost electronic weather instruments for Educational use in Colleges and Schools, so I'm always are looking for that kind of news.

Glad you like the paper, hope the original authors can read your post.

BTW, this other EOR paper cite the SMT100 sensor: The ScaleX campaign: scale-crossing land-surface and boundary layer processes in the TERENO-preAlpine observatory

Good job!

Thanks very much for the reference to the other paper.

Interesting to hear that you are working on low cost electronic weather instruments which is my focus as well. I am still searching for a low cost ultrasonic anemometer and an electronic rain gauge.

Best regards

ChrisRF: Thanks very much for the reference to the other paper.

At your orders. Probably we will find another papers popping out in the near future.

ChrisRF: Interesting to hear that you are working on low cost electronic weather instruments which is my focus as well. I am still searching for a low cost ultrasonic anemometer and an electronic rain gauge.

Best regards

Regarding the two instruments you mentioned, we are stick to the typical and already made ones at this stage: optomechanics for the wind vane; propeller and/or cup type for the anemometer; dipping bucket for the last.

Another options are totally out of our plans due time, human resources and budget constrains.

What about a hot wire anemometer ? You could use an automotive air flow meter , or a pair of thermistors in a tube, one heated ( heat transfer between them ). Look at how automotive rain sensors ( for auto wipers) that use light reflection work for your rain sensor , or buy the Maplin spare part tipping bucket sensor for a few $$