Water & Nutrient Management:
Soil Moisture-Based Irrigation Systems
Time Domain Transmission
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Working Principle
This method measures the one-way time for an electromagnetic pulse to propagate along a transmission line (TL). Thus, it is similar to TDR, but requires an electrical connection at the beginning and ending of the TL. Notwithstanding, the circuit is simple compared with TDR instruments.
Description
The probe has a waveguide design (bent metal rods), so that the beginning and ending of the transmission line are inserted into the electronic block. Alternatively, the sensor consists of a long band (~3 ft), having an electronic block at both ends.
Advantages
- Accurate (±0.01-0.02 ft3ft-3)
- Large sensing soil volume (0.2-1.6 gallons)
- Can be connected to conventional loggers (DC output signal)
- Inexpensive due to standard circuitry
Drawbacks
- Reduced precision, because the generated pulse is distorted during transmission
- Soil disturbance during installation
- 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
