MP406 uses the standing wave principle of measurement. It is equivalent to a Time Domain Reflectometry (TDR) sensor without the need for a complex and expensive pulse generator. MP406 is a high accuracy, precision sensor with 1%VWC accuracy following soil-specific calibration and 0.01%VWC resolution.

• The MP406 is ideally supported by the Soil Moisture Meter (SMM), a wireless, stand-alone logging instrument available from ICT International. With the SMM, MP406 sensors can be individually calibrated for maximum accuracy.
• The SMM can support up to 5 x MP406 sensors.
• For complete monitoring solutions, the MP406 is used in combination with the MP306 soil volumetric moisture content sensor, tensiometers for soil water potential, ICTO2 soil oxygen sensor, or the ICT International automatic weather station.

MP406 Accuracy

The results from measurement of absolute volumetric soil water percent (VSW%) from prepared soil samples using the MP406 are given below (Figure 1). This result is typical of the results obtained from comparative testing of the MP406 in prepared soil samples, for a wide range of agricultural soils.

Standing Wave Technology and hence the MP406 are not affected by changes in temperature or salinity of the soil or material being measured and hence the values of VSW% are equivalent to oven dried water content.

What is Standing Wave?

The standing wave technique uses an oscillator to generate an electrical field in order to detect the dielectric properties of a substrate of interest. The parallel needles of an MP406 act as a coaxial transmission line to generate a signal. The amplitude of the signal is related to the dielectric constant which in turn is directly related to moisture content.

Results

The results from measurement of absolute volumetric soil water percent (VSW%) from prepared soil samples using the MP406 are given alongside. This result is typical of the results obtained from comparative testing of the MP406 in prepared soil samples, for a wide range of agricultural soils. Standing Wave Technology and hence the MP406 are not affected by changes in temperature or salinity of the soil or material being measured and hence the values of VSW% are equivalent to oven dried water content.

Polynomial Look-up Table

Linearization tables can be added to Data Loggers using the following data:
Converting Data Table for MP-406. From VSW% to mV & mA in mineral soil

VSW%	mV MP406	mA MP406C
0%	0	4.00
2%	120	5.71
5%	210	6.99
10%	310	8.43
15%	415	9.93
20%	510	11.285
25%	610	12.71
30%	720	14.285
35%	825	15.785
40%	895	16.785
45%	955	17.64
50%	1005	18.35
55%	1015	18.5
60%	1025	18.64
65%	1035	18.785
70%	1045	18.93
75%	1055	19.07
80%	1065	19.21
85%	1075	19.28
90%	1085	19.43
95%	1105	19.64
100%	1160	20.00