Qingyi FDS-100 Soil Moisture Sensor Three-Pin FDR Frequency Domain Measurement Principle

The soil moisture sensor adopts the FDR frequency domain measurement principle to measure soil moisture content. It is suitable for water-saving agricultural irrigation, greenhouse vegetables, flower gardening, grassland pastures, rapid soil testing, plant cultivation, scientific experiments, and other fields.
Product Overview
Compact and lightweight design, easy to carry and connect.
The soil moisture sensor consists of a power module, transmitter module, zero drift and temperature compensation module, data processing module, etc. The sensor has built-in signal sampling and amplification, zero drift and temperature compensation functions, providing a simple and convenient user interface.

Features
◆ Compact design with high measurement accuracy, fast response speed, and excellent interchangeability.
◆ Good sealing performance, can be directly buried in soil for use, and is corrosion-resistant.
◆ Minimal impact from soil type, widely applicable in various regions.
◆ High measurement accuracy, reliable performance, ensuring normal operation, fast response speed, and high data transmission efficiency.
◆ Supports dielectric constant signal output.

Working Principle
FDR frequency domain measurement utilizes the electromagnetic pulse principle and measures the dielectric constant (ε) of soil based on the propagation frequency of electromagnetic waves in the medium, thereby obtaining the volumetric water content (θv) of the soil.
Technical Parameters
Measurement Parameter: Relative Saturation Moisture Content
Measurement Range: 0～100% (Adjustable Range: 0～60%)
Measurement Accuracy: ±3%
Measurement Stabilization Time: 2 seconds
Response Time: ＜1 second
Measurement Main Frequency: 100 MHz
Protection Rating: IP68
Probe Length: 5.5 cm
Probe Diameter: 3 mm
Probe Material: Stainless Steel
Sealing Material: Epoxy Resin
Measurement Area: A cylinder centered on the central probe with a diameter of 7 cm and height of 7 cm
Response Time: 2 s
Cable Length: 1.5 meters (standard)
Signal Output:
Voltage Type:
Operating Voltage: 5～24V
Operating Current: 3～5mA
Output Signal: 0～2V DC (Customizable 0.4～2V DC)
Current Type:
Operating Voltage: 12～24V
Operating Current: 3～25mA
Output Signal: 0～20mA (Customizable 4～20mA)
RS485 Type:
Operating Voltage: 5～24V
Operating Current: 3～5mA
Output Signal: MODBUS-RTU Protocol
Application Scope
Widely applicable in water-saving agricultural irrigation, greenhouse vegetables, flower gardening, grassland pastures, rapid soil testing, plant cultivation, scientific experiments, and other fields.

FDS-100 Soil Moisture Sensor FDR Frequency Domain Principle