Campbell 229 Specifications
COMPONENTS
229, CE4, and CE8
Water Matric Potential Sensor and Current Excitation Modules
Reliable Water
Measurements
No maintenance required
Overview
Campbell Scientific’s 229 Water Matric Potential Sensor measures
soil water potential from -10 to -2500 kPa. The sensor must be con-
nected to either a CE4 or CE8 current excitation module. A Camp-
bell Scientific datalogger controls the current excitation module,
measures the probe, and calculates soil water matric potential.
www.campbellsci.com/229-l
Benefits and Features
Compatible with most Campbell Scientific dataloggers
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Measures a wide range of matric potential
Measurements not affected by salts in the soil
Long lasting, with no maintenance required
Compatible with AM16/32-series multiplexers allowing
measurement of multiple sensors
questions & quotes: 435.227.9000
229 Measurement Details
The 229 Water Matric Potential Sensor consists of a heating
element and thermocouple placed in epoxy in a hypodermic
needle, which is encased in a porous ceramic matrix.
To calculate soil water matric potential, a CE4 or CE8 current
excitation module applies a 50 mA current to the 229’s heating
element, and the 229’s thermocouple measures the temperature
rise. The magnitude of the temperature rise varies according
to the amount of water in the porous ceramic matrix, which
changes as the surrounding soil wets and dries. Soil water matric
potential is determined by applying a second-order polyno-
mial equation to the temperature rise. Users must individually
calibrate each of their 229 sensors in the soil type in which the
sensors will reside.
A reference temperature measurement is required for the 229’s
thermocouple measurement. Options for measuring the refer-
ence temperature include:
Thermistor built into the CR800, CR850, CR1000, CR3000, or
CR5000 wiring panel
PRT built into the wiring panel of the CR9050 or CR9051E input
module for the CR9000X Measurement and Control System
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The 229 is not compatible with our CR200(X)-series or CR510 dataloggers.