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SPECIFICATIONS
Accuracy: ± 5%
Dimensions: Body is 35mm long, 10mm in diameter;
needles are 30mm long, 0.9mm in diameter.
Temperature Sensors:
10K Precision
Thermistor
Material: epoxy body, stainless steel
needles.
Heater resistance: 32 ohms (1041.5 ohms/m)
Cable length: 2m standard (additional cable
available)
THEORY
The Specific Heat Sensor
consists of a pair of 30mm-long stainless steel needles, spaced
6mm apart. It is a Dual Needle Heat Pulse sensor (DNHP). One
needle contains an Evanohm heater, and the other contains a Precision
10K Thermistor. After the sensor needles are inserted into the
sample, a current is applied to the heater for 8 seconds. The
temperature rise of the thermistor is then monitored. The specific
heat of the material is inversely proportional to the height
of the sensed temperature rise, and the thermal diffusivity of
the material is related to the time taken for the pulse peak
to pass the temperature sensor. The thermal conductivity can
then be computed as the product of the thermal diffusivity and
the specific heat. For more information see the Specific Heat
Sensor manual available from East 30 Sensors.
PUBLISHED PAPERS
Bristow, K.L., R.D. White,
and G.L. Kluitenberg, 1994. Comparison of Single and Dual Probes
for Measuring Soil Thermal Properties with Transient Heating.
Australian Journal of Soil Res. 32:447-464
Bristow, K.L., R.D. White,
and R. Horton, 1994. Measurement of Soil Thermal Properties with
a Dual-Probe Heat Pulse Technique. Soil Sci. Soc. Am. J. 55:291-293
Bristow, K.L., J.R. Bilskie,
G.J. Kluitenberg, and R. Horton, 1995. Comparison of Techniques
for Extracting Soil Thermal Properties from Dual Probe Heat Pulse
Data. Soil Sci. Am. J. 1:160
Campbell, G.S., C. Calissendorff,
and J.H. Williams, 1991. Probe for Measuring Soil Specific Heat
Doing a Heat-Pulse Method. Soil Sci. Soc. Am. J. 55:291-293
Kluitenberg, G.J., J.M.
Ham, and K.L. Bristow, 1993. Error Analysis of the Heat Pulse
Method for Measuring Soil Volumetric Heat Capacity. Soil Sci.
Soc. Am. J. 57:1444-1451
Larson, T.H., 1988. Thermal
Measurements of Soils using a Multi-Needled Probe with a Pulsed
Point-Source. Geophysics 53:266-270.
Taylor, S.A. and Jackson,
R.D. 1986. Heat Capacity and Specific Heat. In "Methods
of Soil Analysis. Part 1. Physical and Mineralogical Methods."
(2nd Ed.) (Ed. A. Klute) ASA Agronomy Monograph No. 9 pp.941-4
de Vries, D.A. (1963).
Thermal Properties of soils. Physics of Plant Environment. (Ed.
W. R. Van Wijk.) pp. 210-35 (North-Holland: Amsterdam)
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