CS655 Reflectómetro contenido agua en suelo, varillas 12cm

Resumen

El CS655 es un sensor inteligente multiparamétrico que usa innovadoras técnicas para monitorizar el contenido de agua volumétrico, conductividad eléctrica y temperatura del suelo. La señal de salida es digital SDI-12, compatible con la mayoría de nuestros dataloggers. Las varillas son más cortas que las del CS650.

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Ventajas y características

  • Un mayor volumen de la muestra reduce el error
  • Medida corregida para efectos de la textura del suelo y conductividad eléctrica
  • Estima el contenido de agua del suelo para una amplia gama de suelos minerales
  • Sensor versátil—mide la permitividad dieléctrica, conductividad eléctrica (EC), y temperatura del suelo

Imágenes

Descripción técnica

The CS655 consists of two 12-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 CS655 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 ≤8 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.

Especificaciones

Measurements Made Soil electrical conductivity (EC), relative dielectric permittivity, volumetric water content, soil temperature
Required Equipment Measurement system
Soil Suitability Short rods are easy to install in hard soil. Suitable for soils with higher electrical conductivity.
Rods Not replaceable
Sensors Not interchangeable
Sensing Volume 3600 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 120 mm (4.7 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 240 g (8.5 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 8 dS/m
Range for Bulk EC 0 to 8 dS/m
Accuracy ±(5% of reading + 0.05 dS/m)
Precision 0.5% of BEC

Relative Dielectric Permittivity

Range 1 to 81
Accuracy
  • ±(3% of reading + 0.8) from 1 to 40 for solution EC ≤ 8 dS/m
  • ±2 (from 40 to 81 for solution EC ≤ 2.8 dS/m)
Precision < 0.02

Volumetric Water Content

Range 0 to 100% (with M4 command)
Water Content Accuracy
  • ±1% (with soil-specific calibration) where solution EC < 3 dS/m
  • ±3% (typical with factory VWC model) where solution EC < 10 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

Compatibilidad

Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.

Dataloggers

Product Compatible Note
CR1000
CR1000X
CR200X (retired)
CR300
CR6
CR800
CR850

Miscellaneous

Product Compatible Note
21X (retired)
CR10 (retired)
CR10X (retired)
CR216X (retired)
CR23X (retired)
CR3000
CR310
CR500 (retired)
CR5000 (retired)
CR510 (retired)
CR9000 (retired)
CR9000X

Información de compatibilidad adicional

RF Considerations

External RF Sources

External RF sources can affect the probe’s operation. Therefore, the probe should be located away from significant sources of RF such as ac power lines and motors.

Interprobe Interference

Multiple CS655 probes can be installed within 4 inches of each other when using the standard data logger SDI-12 “M” command. The SDI-12 “M” command allows only one probe to be enabled at a time.

Optional Installation Tool

CS650G Rod Insertion Guide Tool

The CS650G makes inserting soil-water sensors easier in dense or rocky soils. This tool can be hammered into the soil with force that might damage the sensor if the CS650G was not used. It makes pilot holes into which the rods of the sensors can then be inserted.

Preguntas frecuentes

Número de FAQs relacionadas con CS655: 55

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  1. The permittivity of saturated sediments in a stream bed is expected to read somewhere between 25 and 42, while the permittivity of water is close to 80. A CS650 or CS655 installed in saturated sediments could be used to monitor sediment erosion. If the permittivity continuously increases beyond the initial saturated reading, this is an indication that sediment around the sensor rods has eroded and been replaced with water. A calibration could be performed that relates permittivity to the depth of the rods still in the sediment. 

  2. Damage to the CS650 or the CS655 electronics or rods cannot be repaired because these components are potted in epoxy. Cable damage, on the other hand, may possibly be repaired. For more information, refer to the Repair and Calibration page.

  3. If a system has multiple CS650 or CS655 sensors, it will be necessary to connect many wires to a 12 V supply and many wires to ground. The DIN-Rail Mounting Kit is useful for attaching many wires to the same source in a clean and organized way. For more details, see the 5458 DIN-Rail Terminal Kit instruction manual

    Other methods of connecting several wires together, such as terminal strips or wire nuts, would also work.

  4. The bulk electrical conductivity (EC) measurement is made along the sensor rods, and it is an average reading of EC over that distance at whatever depth the rods are placed.

  5. The volumetric water content reading is the average water content over the length of the sensor’s rods.

  6. Yes, but the pots would have to be large. The CS650 and CS655 can detect water as far away as 10 cm (4 in.) from the rods. If the pot has a diameter smaller than 20 cm (8 in.), the sensor could potentially detect the air around the pot, which would underestimate the water content. In addition, potting soil is typically high in organic matter and clay, causing the probable need for a soil-specific calibration. 

  7. Yes. There is surge protection built into the sensor electronics. The sensor survives a surge of 2 kV at 42 ohm line-to-ground on digital I/O and 2 kV at 12 ohm line-to-ground on power. It also survives a surge of 2 kV at 2 ohm line-to-ground on the rods.

    If additional surge protection is required, consider using the SVP100 Surge Voltage Protector DIN Rail with Mounting Hardware

  8. The CS650 has rods that are 30 cm long, and the CS655 has rods that are 12 cm long. The difference in rod length causes some changes in specifications. For example, the CS650 is slightly more accurate in its permittivity and water content readings, but the CS655 works over a larger range of electrical conductivity. In addition, the CS650 handles a larger measurement volume and provides good accuracy in low EC (electrical conductivity) sand and sandy loam. The CS655 is typically more accurate in soil, works well over a wide range of soil textures and EC, and is easier to install because of its shorter rods.

  9. In soil that has a significant fraction of fines (loam, silt loam, silty clay loam, clay loam, clay), the CS655 is a suitable option because these soils tend to be more electrically conductive, and the CS655 operates over a larger range of electrical conductivity than the CS650. In applications where a smaller measurement volume is desired, such as larger greenhouse pots, the 12 cm long rods of the CS655 are preferable to the 30 cm long rods of the CS650.

  10. The CS650-series sensors have the same rugged epoxy and stainless-steel rods that have been used for water content reflectometers since the CS615-L model was introduced in 1995. There are CS615-L and CS616 sensors in many locations that have been in continuous use for more than ten years with no reported problems. If a CS650 or CS655 remains undamaged by external forces such as lightning, harsh chemicals, or animal actions, the sensor is expected to continue working for decades.