The 257, manfuactured by Watermark, is a solid-state, electrical-resistance sensing device with a granular matrix that estimates soil water potential from 0 to -200 kPa (typically wetter or irrigated soils). It connects directly to your datalogger.Read More
The "-L" on a product model indicates that the cable length is specified at the time of order.
When the amount of water in the soil surrounding the sensor changes, a difference in water potential between the soil and the sensor material is established. This gradient in potential causes a water flux between the two materials. For example, an irrigation or precipitation event results in movement of soil water into the 257 until equilibrium in water potential between the sensor and the soil occurs. An increase in the amount of water in the sensor reduces the electrical resistance between the sensor electrodes.
The datalogger measures the resistance between electrodes, and then converts the resistance measurement to soil water potential by using calibration values supplied with the sensor.
The 257 consists of two concentric electrodes embedded in a reference matrix material. The matrix material is surrounded by a synthetic membrane for protection against deterioration. An internal gypsum tablet buffers against the salinity levels found in irrigated soils. The cable jacket is made of Santoprene rubber, which is resistant to temperature extremes, water, and UV degradation.
The 257's construction can allow the sensor (in some circumstances) to be left in the soil all year, eliminating the need to remove the sensor during fallow periods.
|Measurement Range||0 to -200 kPa|
|Diameter||1.91 cm (0.75 in.)|
|Length||8.26 cm (3.25 in.)|
|Weight||360 g (0.8 lb)|
Number of FAQs related to 257-L: 3
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Not every sensor has different cable termination options. The options available for a particular sensor can be checked by looking in two places in the Ordering information area of the sensor product page:
If a sensor is offered in an –ET, –ETM, –LC, –LQ, or –QD version, that option’s availability is reflected in the sensor model number. For example, the 034B is offered as the 034B-ET, 034B-ETM, 034B-LC, 034B-LQ, and 034B-QD.
All of the other cable termination options, if available, are listed on the Ordering information area of the sensor product page under “Cable Termination Options.” For example, the 034B-L Wind Set is offered with the –CWS, –PT, and –PW options, as shown in the Ordering information area of the 034B-L product page.
Note: As newer products are added to our inventory, typically, we will list multiple cable termination options under a single sensor model rather than creating multiple model numbers. For example, the HC2S3-L has a –C cable termination option for connecting it to a CS110 instead of offering an HC2S3-LC model.
Most Campbell Scientific sensors are available as an –L, which indicates a user-specified cable length. If a sensor is listed as an –LX model (where “X” is some other character), that sensor’s cable has a user-specified length, but it terminates with a specific connector for a unique system:
If a sensor does not have an –L or other –LX designation after the main model number, the sensor has a set cable length. The cable length is listed at the end of the Description field in the product’s Ordering information. For example, the 034B-ET model has a description of “Met One Wind Set for ET Station, 67 inch Cable.” Products with a set cable length terminate, as a default, with pigtails.
If a cable terminates with a special connector for a unique system, the end of the model number designates which system. For example, the 034B-ET model designates the sensor as a 034B for an ET107 system.
Many Campbell Scientific sensors are available with different cable termination options. These options include the following:
Note: The availability of cable termination options varies by sensor. For example, sensors may have none, two, or several options to choose from. If a desired option is not listed for a specific sensor, contact Campbell Scientific for assistance.