Campbell Scientific - Model CS650 - 30 cm Soil Moisture and Temperature Sensor

Detailed Description

The CS650 consists of two 30-cm-long stainless steel rods connected to a printed circuit board. The circuit board is encapsulated in epoxy and a shielded cable is attached to the circuit board for data logger connection.

The CS650 measures propagation time, signal attenuation, and temperature. Dielectric permittivity, volumetric water content, and bulk electrical conductivity are then derived from these raw values.

Measured signal attenuation is used to correct for the loss effect on reflection detection and thus propagation time measurement. This loss-effect correction allows accurate water content measurements in soils with bulk EC ≤3 dS m^-1 without performing a soil specific calibration.

Soil bulk electrical conductivity is also calculated from the attenuation measurement. A thermistor in thermal contact with a probe rod near the epoxy surface measures temperature. Horizontal installation of the sensor provides accurate soil temperature measurement at the same depth as the water content. Temperature measurement in other orientations will be that of the region near the rod entrance into the epoxy body.

Benefits and Features

• More accurate water content measurements in soils with bulk EC up to 3 dS m^-1 without performing a soil-specific calibration
• Larger sample volume reduces error
• Measurement corrected for effects of soil texture and electrical conductivity
• Estimates soil-water content for a wide range of mineral soils
• Versatile sensor—measures dielectric permittivity, bulk electrical conductivity (EC), and soil temperature

Specifications

• Measurements Made: Soil electrical conductivity (EC), relative dielectric permittivity, volumetric water content (VWC), soil temperature
• Required Equipment: Measurement system
• Soil Suitability: Long rods with large sensing volume (> 6 L) are suitable for soils with low to moderate electrical conductivity.
• Rods: Not replaceable
• Sensors: Not interchangeable
• Sensing Volume: 7800 cm3 (~7.5 cm radius around each probe rod and 4.5 cm beyond the end of the rods)
• Electromagnetic: CE compliant
• Meets EN61326 requirements for protection against electrostatic discharge and surge.
• Operating Temperature Range: -50° to +70°C
• Sensor Output: SDI-12; serial RS-232
• Warm-up Time: 3 s
• Measurement Time: 3 ms to measure; 600 ms to complete SDI-12 command
• Power Supply Requirements: 6 to 18 Vdc (Must be able to supply 45 mA @ 12 Vdc.)
• Maximum Cable Length: 610 m (2000 ft) combined length for up to 25 sensors connected to the same data logger control port
• Rod Spacing: 32 mm (1.3 in.)
• Ingress Protection Rating: IP68
• Rod Diameter: 3.2 mm (0.13 in.)
• Rod Length: 300 mm (11.8 in.)
• Probe Head Dimensions: 85 x 63 x 18 mm (3.3 x 2.5 x 0.7 in.)
• Cable Weight: 35 g per m (0.38 oz per ft)
• Probe Weight: 280 g (9.9 oz) without cable

Current Drain

• Active (3 ms):
• 45 mA typical (@ 12 Vdc)
• 80 mA (@ 6 Vdc)
• 35 mA (@ 18 Vdc)
• Quiescent: 135 µA typical (@ 12 Vdc)

Electrical Conductivity

• Range for Solution EC: 0 to 3 dS/m
• Range for Bulk EC: 0 to 3 dS/m
• Accuracy: ±(5% of reading + 0.05 dS/m)
• Precision: 0.5% of BEC

Relative Dielectric Permittivity

• Range: 1 to 81
• Accuracy:
• ±(2% of reading + 0.6) from 1 to 40 for solution EC ≤ 3 dS/m
• ±1.4 (from 40 to 81 for solution EC ≤1 dS/m)
• Precision: < 0.02

Volumetric Water Content

• Range: 0 to 100% (with M4 command)
• Water Content Accuracy:
• ±1% (with soil-specific calibration)
• ±3% (typical with factory VWC model) where solution EC < 3 dS/m
• Precision: < 0.05%

Soil Temperature

• Range: -50° to +70°C
• Resolution: 0.001°C
• Accuracy:
• ±0.1°C (for typical soil temperatures [0 to 40°C] when probe body is buried in soil)
• ±0.5°C (for full temperature range)
• Precision: ±0.02°C