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How to install soil moisture sensors—faster, better, and for higher accuracy

Why installation is everything

If you want accurate data, correct sensor installation should be your number one priority. When measuring in soil, natural variations in density may result in accuracy loss of 2 to 3%, but poor installation can potentially cause accuracy loss of greater than 10%. 

Image of a researcher holding a TEROS-12 soil moisture sensor
TEROS 12 soil moisture sensor

Proper sensor installation is the foundation for the data you collect. If you have a poor foundation, it makes data interpretation difficult. In this article, get insider tips on how to install soil moisture sensors faster, better, and for higher accuracy.  Learn:

  • What to be aware of when installing sensors
  • What installation trouble looks like in your data
  • Installation priorities for soil moisture sensors
  • How METER is advancing the science of installation for higher quality data

Understand your sensors

To understand why poor sensor installation has an enormous impact on the quality of your data, you’ll need to understand how soil moisture sensors work. 

Soil moisture sensors (water content sensors) measure volumetric water content. Volumetric water content (VWC) is the volume of water divided by the volume of soil (Equation 1) which gives the percentage of water in a soil sample.

Image of the equation used to calculate the measure of volumetric water content
Equation 1

So, for instance, if a volume of soil (Figure 1) was made up of the following constituents: 50% soil minerals, 35% water, and 15% air, that soil would have a 35% volumetric water content.

Image of a diagram showing soil constituents in a volume of soil
Figure 1. Soil constituents

Why capacitance sensors work

All METER soil moisture sensors use an indirect method called capacitance technology to measure VWC. “Indirect” means a parameter related to VWC is measured, and a calibration is used to convert that amount to VWC. In simple terms, capacitance technology uses two metal electrodes (probes or needles) to measure the charge-storing capacity (or apparent dielectric permittivity) of whatever is between them.

Image of a diagram depicting how capacitance sensors use two probes to form an electromagnetic field
Figure 2. Capacitance sensors use two probes (one with a positive charge and one with a negative charge) to form an electromagnetic field. This allows them to measure the charge-storing capacity of the material between the probes.

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