TP08
Small size non-steady-state probe for thermal conductivity measurement
Hukseflux is the present market leader in the design of
needle type thermal conductivity sensors.
Many models have been made on customer specification. These include heavy
duty models for field use, small (miniature models for analysis of the
thermal conductivity of small samples, like radioactive materials short
and strong models for use in offshore soil thermal resistivity
measurement.
TP08 is a probe that offers
the possibility to perform a practical and fast measurement of the thermal
conductivity (or thermal resistivity) of the medium in which it is
inserted at a high accuracy level. It works in compliance with the ASTM D
5334-00, D 5930-97 and IEEE 442-1981 standards. The TP08 is a small
version of type TP02, made for situations where the length of TP02 poses a
problem. The standard TP08 probe has proven suitability in soils, thermal
backfill materials, sediments, foodstuff, powders, sludges, paints, glues
and various other materials. The Non-Steady-State Probe (NSSP) measurement
method (also known as transient line source, thermal needle, hot needle,
heat pulse- and hot wire technique) has the fundamental advantages that it
is fast and absolute while the sample size is not critical. Hukseflux is
specialised in NSSP design. Special models have been developed for in-situ
field experiments. For permanent installation in soils, a dedicated model,
TP01, is available. TP08 has been designed and tested in collaboration
with the Applied Physics Group of Wageningen University.
Free: For a nice clear print of the original product
brochure (PDF) click here.
TP08 is very often used with Campbell
Scientific CR10X. A manual
on application of TP02 with CR10X is obtainable
here; TP02 is used in exactly the same manner as TP08. More details on
the science: non-steady state probe science.
Figure 1 TP08 Small Size
Non-Steady-State Probe: The probe consists of a needle (3) with a single
thermocouple junction (6) and a heating wire, (5). It is inserted into the
medium that is investigated. In the base, (2), a temperature sensor, (4),
is mounted. All dimensions are in mm.
INTRODUCTION
The standards of the American
Society for Testing and Materials (ASTM) and Institute of Electrical and
Electronics Engineers (IEEE) describe proven methods for determining the
thermal conductivity of materials.
ASTM D 5334-00 and D 5930-97 and
IEEE Std 442-1981 " Standard Test Methods" specify the use of
Non-Steady-State Probes (NSSP) in various applications. In general a NSSP
consists of a heating wire, representing a perfect line source, and a
temperature sensor capable of measuring the temperature at this source.
The probe is inserted in the medium that is investigated. The NSSP
principle relies on a unique property of a line source: after a short
transient period the temperature rise, ∆T, only depends on heater power,
Q, and medium thermal conductivity, λ:
∆T = (Q / 4 π λ) (ln t + B)
With ∆T in K, Q in W/m, λ in W/mK,
t the time in s and B a constant. By measuring the heater power, and
tracing the temperature in time (for TP08 typically during 2 minutes), λ
can be calculated. The sample size is not critical, as long as a 20 mm
radius around the needle is covered.
The measurements of Q, t and ∆T
are all direct measurements of power, time, and temperature respectively.
These are done without need of reference materials. The measurement with
TP08 is absolute.
TP08 can be obtained as a separate
probe for incorporation in the user's measurement and control system. It
is suitable for operation with the Campbell Scientific CR10X.
TP08 DESIGN
Hukseflux specialises in
Non-Steady-State probe design. The primary model of the Hukseflux product
range is the TP02. This model offers optimal measurement accuracy by a
combination of its design features.
For some applications however the
requirements regarding the sample size are such that the needle length and
diameter of TP02 are too large.
For this category of samples, TP08
has been designed.
Having a needle length of 70 mm,
with the junction at around 17 mm from the tip, and a diameter of 1.2 mm,
samples of around 80 ml can be analysed. (35 mm depth). In some cases
samples can even be smaller (consult Hukseflux).
In TP08 the reference junction of
the thermocouple is located in the base. A high quality measurement with
TP08 requires that not only the sample but also the base are at a stable
(preferably the same) temperature.
Usually this is achieved by
clamping the base into the same material (metal) that holds the sample.
Figure 2
The signal of TP08 as a function of the natural logarithm of time (ln(t)).
After a transient period the graphs show linear behaviour. In this phase the
slope of the graph is inversely proportional to the thermal conductivity λ.
CALIBRATION / ISO 9000
Verification of the stability of
the total probe can be done by repeated (yearly) testing in glycerol,
preferably at several temperatures. Alternatively Calibration Reference
Cylinders (CRC) traceable to NPL can be purchased at Hukseflux. TP08 is
suitable for use by ISO certified labs.
SUGGESTED USE
OPTIONAL: CONTAINER TP08
Because of the relative importance
of the thermal equilibrium between base and sample, an optional container
can be ordered with TP08.
MORE INFORMATION / OPTIONS
Standards: ASTM standards can be
obtained from ASTM at http://www.astm.org.
Alternative designs: Hukseflux is
specialised in NSSP design. Alternative models, for instance smaller, more robust
or temperature resistant have been manufactured on request.
Permanent installation in soils:
The dedicated model TP01 is specifically designed for long term
monitoring. A separate brochure is available.
Solutions for measurement and
control: See the TP08 manual or inquire at Hukseflux. A program for
Campbell Scientific CR10X is available. Turn key systems are offered for
sale: see TPSYS.
Manuals: The TP08 manual is
available free of charge as a PDF file via
e-mail.
NEW!
- For high accuracy calibration CRC Calibration
Reference Cylinders are available.
- For insertion into hard soils
GT Series Guiding tubes can be applied.
TP08
SPECIFICATIONS
-
Test
method: ASTM D 5334-00 and D 5930-97
IEEE Std 442-1981
-
Needle length: 70 mm
-
Traceability: NPL
-
Range (λ):
0.1 to 6 W/m.K
-
Sensitivity (∆T): Thermocouple
K, ANSI MC96.1-1982
-
Temperature range
(total sensor including cable): -55 to +180
°C
-
Accuracy (@ 20 °C): +/- (3% + 0.02) W/mK
-
Temperature
dependence of the accuracy: +/- 0.02 %/K
(additional)
-
Measurement cycle duration: 200 s
(typical)
-
Power requirements (switched) : 3 V, 1
Watt (max)
-
Medium / sample
requirements: Granular materials, powders, slurries, gels, pastes. Some
samples require pre-drilling. Sample size: Min 20 mm radius. Min volume
80 ml. Smaller samples: consult Hukseflux. Caution: please consult the product manual for more details.
-
Protection needle and base: IP 68
-
Protection total sensor: IP 67
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