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AquaSpy Vector Probe Measurement Accuracy

As you install an AquaSpy Soil Monitoring System you may ask yourself, how accurate does it actually measure?  The answer may surprise you:  the AquaSpy Vector probe is very accurate but that is not what actually matters.

Here is why.  Soil probes pick up information from the soil using different methods.  Most probe systems are using the fact that water has a much higher permittivity than dry soil.  Therefore, the measurement that comes out of the probe is not truly a measurement of water but of soil permittivity. The probe has no means of separating the permittivity from soil and other solids from water permittivity.  Fortunately, the water permittivity is significantly higher than solid permittivity. To make matters more difficult, the measured permittivity has two main components – water and electrical conductivity (EC).  Most multi-sensor probes are poorly designed and cannot separate the permittivity measurement into moisture and conductivity.  Additionally, some probes have significant temperature drift on the measurement.  That all boils down to:

  • Can your probe separate moisture from conductivity?
  • Does it provide accurate measurements when the ambient temperature changes (for all sensors)?
  • Is the sensor capable of repeating the same measurement with minimum sample to sample variation?
  • Will the probe require recalibration with each install?

The AquaSpy Vector probe can separate moisture from conductivity, it has no temperature drift, and it only needs one calibration at our manufacturing location. The sample to sample variation is below 0.05%

Once you have a probe that can accurately measure moisture you should think you are all set. But that is actually not the case.  Each sensor is placed in a particular soil condition that has a certain field capacity or full point (water holding capacity).  So even if you know the moisture level, it does not say anything about how much moisture is actually available. It’s just a number. You still need to figure out how much water can the soil hold, and additionally, you also need to know when the particular crop will run out of water given the soil it’s planted in.

Most systems will just give you a reading, say 65. That is a dimensionless number. It’s usually derived from the permittivity reading that the sensor observed. In that case, water represents a reading ~80 (depending on temperature) and a number of 1 represent air.  Some systems will claim that they can convert that reading to inches of water, but that is simply not possible unless you are in a controlled lab condition.  However, the AquaSpy system has a unique and patented method of automatically calculating how much water is available. To go even further, the system will also provide you with the amount of water in the active root zone.

Conclusion:

Measuring the soil permittivity is almost meaningless. Even if you can measure it very accurately. Yes, it indicates how much water there may be available; however, the data must be post processed to turn it into something that accurately depicts what is truly available to the plant.

As the only system on the market, the AquaSpy system does indeed provide this information in a concise and at-a-glance user interface using 12 sensors across 48”.  Through our proprietary technology, AquaSpy delivers the most meaningful data to enable our growers to control what they can and boost yields. The accuracy is so good that sensor data from each layer zone has its own full and refill points so holding capacity determines soil type by layer, rather than proclaiming soil type and having the sensor calibrated to measure moisture content on a scale calibrated for that proclaimed soil type. The AquaSpy probe is completely unique in the current market space for being cost effective, accurate, and multi-dimensional.