CS655 Bodenfeuchtesensor 12cm

Überblick

Der CS655 ist ein Multiparametersensor der mit Hilfe einer innovativen Technik den volumetrischen Wassergehalt, elektrische Leitfähigkeit und Temperatur des Bodens bestimmt. Er gibt ein SDI-12 Signal aus, das von fast allen unseren Loggern gelesen werden kann. Er hat kürzere Stäbe als der CS650 zum Einsatz in schwierigeren Böden.

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Funktionen und Vorteile

  • Größeres Probenvolumen reduziert Fehler
  • Messwerte werden korrigiert zur Vermeidung von Effekten durch verschiedene Bodenarten und elektrische Leitfähigkeiten
  • Kalkuliert Badenwassergehalt für viele mineralische Böden
  • Vielseitiger Sensor, misst elektrische Leitfähigkeit, volumetrischen Wassergehalt, Dielektrizitätskonstante und Temperatur

Bilder

Technische Beschreibung

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.

Spezifikationen

Measurements Made Soil electrical conductivity (EC), relative dielectric permittivity, volumetric water content (VWC), 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

Kompatibel mit

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

Datenlogger

Product Compatible Note
CR1000 (retired)
CR1000X
CR300
CR3000
CR310
CR350
CR6
CR800 (retired)
CR850 (retired)

Additional Compatibility Information

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.

FAQs für

Number of FAQs related to CS655: 55

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  1. The CS650 and CS655 are warranted by Campbell Scientific to be free from defects in materials and workmanship under normal use and service for 12 months from the date of shipment. For further details, see the “Warranty” section of the CS650/CS655 manual.

  2. 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. 

  3. Mine tailings are highly corrosive and have high electrical conductivity. Some customers have successfully used water content reflectometers, such as the CS650 or the CS655, to measure water content in mine tailings by coating the sensor rods with heat-shrink tubing. This affects the sensor output, and a soil-specific calibration must be performed. Care must be taken during installation to avoid damaging the heat-shrink tubing and exposing the sensor’s rods.  In addition, covering the sensor’s rods invalidates the bulk electrical conductivity reading. Unless the temperature reading provided by the CS650 or the CS655 is necessary, a better option may be to use a CS616 with coated rods.

  4. The CS650 and the CS655 are not ideal sensors for measuring water level. However, these sensors do respond to the abrupt change in permittivity at the air/water interface. A calibration could be performed to relate the period average or permittivity reading to the distance along the sensor rods where the air/water interface is located. From that, the water level can be determined. The permittivity of water is temperature dependent, so a temperature correction would be needed to acquire accurate results.  

  5. The electrical conductivity (EC) of sea water is approximately 48 dS/m. The CS655 can measure permittivity in water with EC between 0 and 8 dS/m. EC readings become extremely unstable at conductivities higher than 8 dS/m and are reported as NAN or 9999999. Because EC is part of the permittivity equation, an EC reading of NAN leads to a permittivity reading of NAN as well. Thus, the CS655 cannot provide good readings in sea water.

    With regard to sea ice, the electrical conductivity drops significantly when sea water freezes and the permittivity changes from approximately 88 down to approximately 4, as the water changes from a liquid to a solid state. With both EC and permittivity falling to levels that are within the CS655 measurement range, the sensor is expected to give valid readings in sea ice. The sensor is rugged and can withstand the cold temperatures. However, as the ice melts, there will be a point at which the electrical conductivity becomes too high to acquire a valid reading for either permittivity or electrical conductivity.

  6. No. The abrupt permittivity change at the interface of air and saturated soil causes a different period average response than would occur with the more gradual permittivity change found when the sensor rods are completely inserted in the soil. 

    For example, if a CS650 or a CS655 was inserted halfway into a saturated soil with a volumetric water content of 0.4, the sensor would provide a different period average and permittivity reading than if the probe was fully inserted into the same soil when it had a volumetric water content of 0.2.

  7. 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. 

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

  9. 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.

  10. Probably not. The principle that makes these sensors work is that liquid water has a dielectric permittivity of close to 80, while soil solid particles have a dielectric permittivity of approximately 3 to 6. Because the permittivity of water is over an order of magnitude higher than that of soil solids, water content has a significant impact on the overall bulk dielectric permittivity of the soil. When the soil becomes very dry, that impact is minimized, and it becomes difficult for the sensor to detect small amounts of water. In air dry soil, there is residual water that does not respond to an electric field in the same way as it does when there is enough water to flow among soil pores. Residual water content can range from approximately 0.03 in coarse soils to approximately 0.25 in clay. In the natural environment, water contents below 0.05 indicate that the soil is as dry as it is likely to get. Very small changes in water content will likely cause a change in the sensor period average and permittivity readings, but, to interpret those changes, a very careful calibration using temperature compensation would need to be performed.