More accurate in soils with high bulk EC
Overview
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.
Read MoreBenefits and Features
- 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
Images
Detailed Description
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.
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Compatibility
Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.
Data Loggers
| Compatible | Note | |
|---|---|---|
| CR1000 (retired) | ||
| CR1000X (retired) | ||
| CR300 (retired) | ||
| CR3000 (retired) | ||
| 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.
Specifications
| 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) |
|
| 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 |
|
| Precision | < 0.02 |
Volumetric Water Content |
|
| Range | 0 to 100% (with M4 command) |
| Water Content Accuracy |
|
| Precision | < 0.05% |
Soil Temperature |
|
| Range | -50° to +70°C |
| Resolution | 0.001°C |
| Accuracy |
|
| Precision | ±0.02°C |
Related Documents
Downloads
CS650 / CS655 Firmware v.2 (429 KB) 02-12-2015
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.
FAQs for
Number of FAQs related to CS655: 55
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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.
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Modifications to the CS650 or CS655, including shortening the cable, will void the warranty. However, shortening the cable will not affect the sensor’s performance. If a decision is made to shorten the cable, care should be taken to avoid damaging the cable jacket and exposing bare wire except at the ends that connect to the data logger or multiplexer terminals.
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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.
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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.
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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.
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The CWS655 is a wireless sensor with measurement electronics, radio, and power supply all integrated in a single device. The CWS655, however, requires the use of a CWB100 base station radio connected to a data logger. Only the rods of the CWS655 should be buried in the soil; burying the body of the CWS655 will prevent the sensor from communicating with the CWB100.
The CS655 is a cabled multiparameter smart sensor that sends data by RS-232 serial or SDI-12 communication through a direct connection to a data logger. The CS655 is suitable for burial at any depth.
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The volumetric water content reading is the average water content over the length of the sensor’s rods.
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A thermistor is encased in the epoxy head of the sensor next to one of the stainless-steel rods. This provides an accurate point measurement of temperature at the depth where that portion of the sensor head is in contact with the soil. This is why a horizontal placement is the recommended orientation of the CS650 or CS655. The temperature measurement is not averaged over the length of the sensor rods.
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The cable properties and power requirements of the CS650 and the CS655 are such that communication with a data logger may work for cable lengths greater than 2,000 ft. If multiple sensors are communicating through the same universal or control terminal, the total length of all of those sensors must not exceed 2,000 ft.
In practice, it is less expensive to purchase a new data logger than to buy a CS650 or CS655 with 2,000 ft of cable. If the cable is run through conduit, or if a 2,000 ft long trench needs to be excavated, then the installation cost becomes more expensive than buying another data acquisition system and sensors with shorter cables.
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Because the reported volumetric water content reading is an average taken along the entire length of the rods, the sensor should be fully inserted into the soil. Otherwise, the reading will be the average of both the air and the soil, which will lead to an underestimation of water content. If the sensor rods are too long to go all the way into the soil, Campbell Scientific recommends inserting the rods at an angle until they are fully covered by soil.