More accurate in soils with high bulk electrical conductivity
Overview
The CS650 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.
Note: The cable termination options for this sensor are not suitable for use with an ET107 station. For this type of station, use the CS650-LC sensor instead, which has a suitable cable connector.
Read MoreBenefits 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
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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.
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) |
|
| 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 |
|
| 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 |
Compatibility
Note: The following shows notable compatibility information. It is not a comprehensive list of all compatible or incompatible products.
Data Loggers
| Product | Compatible | Note |
|---|---|---|
| CR1000 (retired) | ||
| CR1000X | ||
| CR300 | ||
| 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 CS650 sensors 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.
Installation 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 were not used. It makes pilot holes into which the rods of the sensors can then be inserted.
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.
Frequently Asked Questions
Number of FAQs related to CS650: 54
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The electrical conductivity (EC) of sea water is approximately 48 dS/m. The CS650 can measure permittivity in water with EC between 0 and 3 dS/m. EC readings become extremely unstable at conductivities higher than 3 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 CS650 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 CS650 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.
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No. 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. Gasoline and other hydrocarbons have dielectric permittivities in the same range as soil particles, which essentially make them invisible to the CS650 and the CS655.
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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.
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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.
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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 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.
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Campbell Scientific strongly discourages shortening the sensor’s rods. The electronics in the sensor head have been optimized to work with the 30 cm long rods. Shortening these rods will change the period average. Consequently, the equations in the firmware will become invalid and give inaccurate readings.
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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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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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