The CS655 is a multiparameter smart sensor that uses innovative techniques to monitor soil volumetric-water content, bulk electrical conductivity, and temperature. It outputs an SDI-12 signal that many of our data loggers can measure. It has shorter rods than the CS650, for use in problem soils.
Note: The cable termination options for this sensor are not suitable for use with an ET107 station. For this type of station, use the CS655-LC sensor instead, which has a suitable cable connector.Leia mais
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.
|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.|
|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|
|Active (3 ms)||
|Quiescent||135 µA typical (@ 12 Vdc)|
|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|
Volumetric Water Content
|Range||0 to 100% (with M4 command)|
|Water Content Accuracy||
|Range||-50° to +70°C|
Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.
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.
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.
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.
Current CS650 and CS655 firmware.
Note: The Device Configuration Utility and A200 Sensor-to-PC Interface are required to upload the included firmware to the sensor.
Number of FAQs related to CS655: 55
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No. The equation used to determine volumetric water content in the firmware for the CS650 and the CS655 is the Topp et al. (1980) equation, which works for a wide range of mineral soils but not necessarily for artificial soils that typically have high organic matter content and high clay content. In this type of soil, the standard equations in the firmware will overestimate water content.
When using a CS650 or a CS655 in artificial soil, it is best to perform a soil-specific calibration. For details on performing a soil-specific calibration, refer to “The Water Content Reflectometer Method for Measuring Volumetric Water Content” section in the CS650/CS655 manual. A linear or quadratic equation that relates period average to volumetric water content will work well.
A CS650 or CS655 can be ordered with an SDI-12 address option of -VS. With the -VS option, the SDI-12 address is set at the factory before the sensor is shipped. The last digit of the sensor’s serial number becomes that sensor’s SDI-12 address. Typically, the -VS option is chosen when there are multiple sensors that will communicate with the data logger on the same SDI-12 communications terminal.
If the -VS option is not selected when ordering, the CS650 or CS655 will ship with its SDI-12 address set to 0 (the default -DS option). The address can be changed to a non-zero value using the A200 Sensor to PC Interface or by connecting the sensor to an SDI-12 communications terminal and sending the aAb! Command as described in the “SDI-12 Sensor Support” appendix of the CS650/CS655 manual.
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.
Yes. Keeping the sensor rods parallel during installation is especially difficult in gravel, but it can be done. Gravel has large pore spaces that drain quickly, so the water content readings will likely show rapid changes between saturation and very dry. If small changes of water content at the dry end are of interest, a soil-specific calibration may need to be performed to convert period average directly to volumetric water content.
No. The temperature sensor is located inside the sensor’s epoxy head next to one of the sensor rods. The stainless-steel rods are not thermally conductive, so the reported soil temperature reading is actually the temperature of the sensor head. If the CS650 or the CS655 is installed horizontally, which is the preferred method, then the sensor head will be at the same temperature as the soil, and the soil temperature value will be accurate. However, if the sensor is installed vertically, and/or with the sensor head above ground, the soil temperature reading will be less accurate. Because the sensor orientation is not known, no temperature correction was written into the firmware.
The CS650/CS655 manual gives a temperature correction that works in coarse sand, but it should be used cautiously with other soil types. If a temperature correction is required, it is best to determine a soil-specific temperature correction.
When correcting for temperature, the following effects contribute to the sensor output:
The interaction of these effects may be complicated. For example, with increasing temperature, two things happen at the same time: the falling permittivity of water is decreasing the period average, and the increasing EC is increasing the period average. The net result as to whether the period average goes up or down depends on how conductive the soil is and the contributions of the other temperature effects.
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.
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.
In soil that is sandy, sandy loam, or loamy sand with low electrical conductivity, the CS650 is a suitable option because it has slightly better accuracy specifications than the CS655 and a larger measurement volume.