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THERMAL
PROPERTIES SENSOR
GT-ATX
SERIES
GUIDING TUBES FOR
THERMAL NEEDLES TP02, TP08 AND TP07
The GT-ATX series guiding tubes are
accessories for Non-Steady-State Needle probes. They are intended to facititate
measurements in hard soils, concrete, cement and bentonite. Also in case of
measurements on large quantities of samples one can use several guiding tubes
and one single needle.
Figure 1.
Non-Steady-State Probe. The
needle (1) is inserted into a guiding tube (2), typically in a solid sample
(3).
INTRODUCTION
- None-Steady-State Probes are used to determine
the thermal conductivity of the surrounding medium. The method can applied in
various substances such as sludges, fluids, foodstuff. The most frequest
application however is in soils.
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- A recurring problem is that insertion into
hard soils, bentonites and cements is quite difficult.
- The main problem is that it is quite difficult
to insert needles into these hard materials.
- The use of guiding tubes in many cases can
solve this problem;
- The guiding tube should be inserted into the
medium, and the needle can be inserted at a later stage.
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- LICHTZEN
AE / AITNIX is a leading supplier of
Non-Steady-State Probes, and is the inventor of this guiding tube
technology.
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APPLICATIONS
- In case of bentonites and cement the guiding
tubes are cast into the material and experiments can be carried out
later
- In case of hard soils, a typical approach is
to pre-drill a hole, insert the guidig tube, compact the soil again, and perform
a measurement.
- In case of dryout experiments guiding tubes
are inserted into the samples, dryout can then take place at high temperature
(the needle is not inserted).
- Figure 2: guiding tubes
in a soil (1) sample.
- Caps (4) are used to avoid soil coming into
the tubes. GT-ATX01 (2), GT-ATX02 (3) and GT-ATX03 (5) have different dimensions to suit
different needle types.
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ACCURACY CONSIDERATIONS
- It has been verified that the addition of a
guiding tube does not have a significant impact on the measurement accuracy;
when inserting a needle to a guiding tube, essentially a larger diameter needle
is created. This results in a larger transient time; one has to wait longer
before the desired linear behaviour (of temperature versus the logarithm of
time) is occurring.
- This is normal behaviour for thicker
needles.
- In case it is possible, it is recommended to
add a small quantity of glycerol into the guiding tube (before inserting the
needle) to minimise the contact resistance. This improves the repretability of
the measurement. One should however be careful not to pollute the soil with the
glycerol.
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- Type
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- Dimensions
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- Suitability for needle
types
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- GT-ATX01
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- L = 90
- OD = 2
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- TP08
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- GT-ATX02
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- L = 170
- OD = 2.38
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- TP02
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- GT-ATX03
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- L = 150
- OD = 4.50
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- TP07
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Table 1: GT-ATX guiding tube types and their
application.
DIRECTIONS FOR USE
- 1 put the GT-ATX into the medium
- 2 cast or compact as much as
possible
- 3 remove the cap
- 4 (optional) put a small quantity of glycerol
into the GT-ATX. Make sure not to spill glycerol on the soil.
- 5 put the needle into the GT-ATX
- 6 perform an experiment however increase the
heating time by 50% relative to the normal situation
- 7 remove the needle
- 8 put the cap onto the GT-ATX
- 9 if applicable: remove the GT-ATX from the sample
(in many cases the GT-ATX can be re-used).
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GT-ATX SPECIFICATIONS
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Test method: ASTM D 5334-00 and
D 5930-9, IEEE Std 442-1981
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Delivery: sets of 5 tubes, including caps
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Material: stainless steel
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Needle ends: welded
- Protection tube
with cap: IP 67
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