Water & Nutrient Management:
Soil Moisture-Based Irrigation Systems
Phase Transmission
Working Principle
After having traveled a fixed distance, a sinusoidal wave will show a phase shift relative to the phase at the origin. This phase shift depends on the length of travel along the TL, the frequency and the velocity of propagation. Since velocity of propagation is related to soil moisture content, for a fixed frequency and length of travel soil water content can be determined by this phase shift.
Description
The probe uses a particular waveguide design (two open concentric metal rings), so that phase measuring electronics can be applied at the beginning and ending of the waveguides.
Advantages
- Accurate with soil-specific calibration (±0.01 ft3ft-3)
- Large sensing soil volume (4-5 gallons)
- Can be connected to conventional loggers (DC output signal)
- Inexpensive
Drawbacks
- Significant soil disturbance during installation due to concentric rings sensor configuration
- Requires soil-specific calibration
- Sensitive to salinity levels >3 dS/m
- Reduced precision, because the generated pulse gets distorted during transmission
- Needs to be permanently installed in the field
This page was last updated on June 15, 2010.
Videos
- Welcome and Outline of Contents
- Timed Irrigation
- Bypass Timer Irrigation
- On-Demand Irrigation
- Irrigation Components
- Soil Moisture Sensors
- Irrigation Sensor Placement
- Application of the System
- Irrigation Sensor Families
- Neutron Probe
- Time Domain Reflectometry
- Capacitance Probe
- Combined Probe
- Frequency Domain Reflectometry (FDR)
- Amplitude Domain Reflectometry
- Phase Transmission
- Time Domain Transmission
- Tensiometer
- Gypsum Block
- Granular Matrix Sensors (GMS)
- Heat Dissipation
- Soil Psychrometer
