What is the difference between the FDR method and the capacitance method of VMC measurement? Are they the same?
They are technically not the same. For the strictest technical accuracy, FDR makes a frequency scan and capacitance measures the charge time of a capacitor. From a practical standpoint there is little difference in the performance.
How can I perform a SOIL SENSOR CALIBRATION?
The SOIL SENSOR CALIBRATION written instructions are here. Watch the video for soil-specific calibration here.
One of the advantages of digital sensors is the ability to update their programming (firmware) without sending the sensors back to METER or even excavating them from the field. While it is seldom necessary to update sensors, we do recommend updates on occasion to improve probe performance or resolve problems. Please contact your METER representative before updating any of your sensors.
Updating sensors using ProCheck
If the need does arise to update the program on your sensors, you will need:
A computer that can run Windows or a Windows emulator.
A ProCheck handheld reader.
The relevant updater provided by your METER representative.
Please follow these steps to update the sensor:
Install the updater file onto your computer. It can typically be acquired through a web link provided by your METER representative.
Connect your METER digital sensor to your ProCheck through the stereo connector or pigtail to stereo adapter if you have sensors with bare leads.
Connect the ProCheck to your computer using the serial to USB adapter included in the ProCheck kit. If you do not have any METER software installed on your computer, you will need to install the USB driver. Please close any open METER software.
Run the updater from your computer.
The update should take 3 – 5 minutes. You can see the current version of firmware that your sensor is running in the lower left corner of your ProCheck screen when it is reading the sensor. Please contact us if you require a firmware update but do not own a ProCheck. We may be able to arrange a loaner. Do not hesitate to contact [email protected] or call 509-332-5600 if you have any questions.
Why don't your soil moisture sensors measure with 1% accuracy like some others spec'd?
There are two elements to the accuracy of time-domain reflectometry (TDR), frequency domain reflectometry (FDR), and capacitance sensors:
How well the sensors measure the dielectric permittivity of the soil; and
How well the calibration converts that measurement to water content.
Due to inherent variability in soil physical properties, it is impossible for a dielectric sensor to measure within 1% water content accuracy across a broad range of soil types, even with a perfect measurement of dielectric permittivity. Beware sensors that claim an unbelievable accuracy in all substrates.