No maintenance required
Overview
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 data logger.
Read MoreBenefits and Features
- Survives freeze-thaw cycles
- Compatible with most Campbell Scientific data loggers
- Contains blocking capacitors in its cable that minimize galvanic degradation and measurement errors due to ground loops
- Buffers salts in soil
- Rugged, long-lasting sensor
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Detailed Description
The 257 determines soil water potential by measuring electrical resistance. When the 257 is wet, electrical resistance is low. As the 257 dries, resistance increases.
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 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.
Specifications
| Diameter | 1.91 cm (0.75 in.) |
| Length | 8.26 cm (3.25 in.) |
| Weight | 360 g (0.8 lb) |