COMPONENTS
229, CE4, and CE8
Water Matric Potential Sensor and Current Excitation Modules
Reliable Water
Measurements
No maintenance required
Overview
Campbell Scientic’s 229 Water Matric Potential Sensor measures
soil water potential from -10 to -2500 kPa. The sensor must be connected to either a CE4 or CE8 current excitation module. A Camp-
Benets and Features
Compatible with most Campbell Scientic dataloggers
Measures a wide range of matric potential
Measurements not aected by salts in the soil
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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-
bell Scientic datalogger controls the current excitation module,
measures the probe, and calculates soil water matric potential.
Long lasting, with no maintenance required
Compatible with AM16/32-series multiplexers allowing
measurement of multiple sensors
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 reference 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
1
e 229 is not compatible with our CR200(X)-series or CR510 dataloggers.
questions & quotes: 435.227.9000
www.campbellsci.com/229-l
Campbell Scientic, Inc.
815 W 1800 N
Logan, UT 84321-1784
(435) 227-9000
www.campbellsci.com
Current Excitation Modules
Either a CE4 or CE8 current excitation module can provide a constant current to the heating element of the 229. The CE4 sources
current for up to four 229s, and the CE8 sources current for up to
eight. Both modules require a 12 Vdc power source.
The number of 229 sensors measured by one datalogger can be
increased by connecting a CE4 or CE8 to one or more AM16/32series multiplexers2. Up to four multiplexers can be connected to
the CE4, and up to eight multiplexers can be connected to the CE8.
The CE4 can source current for four 229 sensors directly.
The outputs of the CE4 can be connected to as many as
four multiplexers, greatly expanding system capacity.
Ordering Information
Water Matric Potential Sensor
229-L Heat Dissipation Matric Potential Sensor with user-specied lead
length. Enter lead length, in feet, after the -L. Recommended
length is 25, 50, 75, or 100 ft (8, 15, 23, or 31 m). Must choose a
cable termination option (see below).
Cable Termination Options (choose one)
-PT Cable terminates in stripped and tinned leads for direct con-
nection to a datalogger/current excitation module terminals.
-PW Cable terminates in a connector for attachment to a
prewired enclosure.
Specications
229 Water Matric Potential Sensor
Measurement Range: -10 kPa to -2500 kPa
Measurement Time: 30 s typical
Thermocouple Type: copper/constantan (type T )
Heater Resistance: ~34 Ω
Resolution: ~1 kPa at matric potentials < -100 kPa
Diameter: 1.5 cm (0.6 in)
Length: 6.0 cm (2.4 in)
Sensor Weight: 10 g (0.35 oz)
Cable Weight: ~23 g/m (0.25 oz/ft)
The CE8 can source current for eight 229 sensors directly.
The outputs of the CE8 can be connected to as many as
eight multiplexers, greatly expanding system capacity.
Current Excitation Modules (choose one)
CE4 Four-Channel Current Excitation Module
CE8 Eight-Channel Current Excitation Module
Cable for Current Excitation Modules
CABLE3CBL-L 22-AWG, three-conductor cable with user-specied lead
length. Enter lead length, in feet, after the -L. This cable
can be used to connect a CE4 or CE8 to the datalogger.
CE4/CE8 Current Excitation Modules
Output: 50 mA ±0.25 mA, regulated
Output Channels
CE4: 4
CE8: 8
Power: 12 Vdc source required
Active Current Drain:
25 mA + (50 mA) x (number of 229s connected to the CE4 or CE8)
Dimensions
CE4: 11.5 x 5.4 x 2.7 cm (4.5 x 2.1 x 1.1 in)
CE8: 16.5 x 5.4 x 2.7 cm (6.5 x 2.1 x 1.1 in)
Weight
CE4: 131 g (4.6 oz)
CE8: 184 g (6.5 oz)
2
e CE4 and CE8 modules switch currents that are greater than 30 mA, which degrades the contact surfaces of the mechanical relays.
erefore the multiplexer channels to which the CE4 or CE8 have been connected may become unsuitable for other applications (refer to the
multiplexer manual for more information).
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© 2003, 2013
Campbell Scientic, Inc.
July 19, 2013
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