TP01 Info note
Application as sensor for ultra low wind speeds and sensor for leaf boundary layer conductance
In combination with a proper data acquisition and control system, TP01 can be
used to investigate the heat transfer coefficient, Ctr, from its
surface to the air. The obtained data can be used to determine other transfer
coefficients (for instance for vapor transport ) or local wind speed
(specifically in the low wind speed range). Both measurements are qualitative
rather than absolute.
More details on the science: heat flux
and transfer. Hukseflux has prepared a special memo on this application that can be
obtained by e-mail. You can also see the
normal TP01 brochure.
For a free copy of the product brochure and this application note click here.
TP01 consists of a heater and a sensor incorporated in a very thin plastic
foil. The sensor in TP01, consisting of two thermopiles, performs a differential
temperature measurement around the heating wire with record breaking
sensitivity.
When placing the sensor in air and switching on the heater, the sensor output
will be inversely proportional to the heat transfer to the air. As such TP01 can
be used to study local wind speed in the 0.1 to 2 m/s region, for instance in
greenhouses and buildings. Another possibility is to use TP01 as an artificial
leaf to study mass transport in the leaf boundary layer. The sensor behavior is
similar to that of hot wire anemometers and heated "artificial
leaves".
Measurement errors induced by solar radiation are strongly reduced by the
fact that the sensor is symmetrically placed around the wire, and by using the
technique of pulsed heating. The low thermal mass makes TP01 very fast, reaching
thermal equilibrium in 30 s in still air. Every minute the zero offset can be
determined.
When considering to apply TP01 for measurement of ultra low wind speeds and
leaf boundary layer conductance, it is recommended to consult the memo on this
subject, which is available at Hukseflux.
A program for interfacing with the Campbell Scientific CR10X is available.
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| Figure 1 the layout of
TP01 thermal properties sensor. The heating wire A created a cylindrical
thermal gradient. Thermopiles B and C measure the temperature gradient,
which in case of this application depends on the heat transfer to the air.
A and B are connected in series, and create one single output. The cable
is made of polyurethane (PUR). |
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| Figure 2 the output of
TP01 after heating. The steady state output depends on the transfer to the
air. This transfer is governed by the transfer coefficient, Ctr,
which is directly related to the wind speed. |
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Suggested use
- As "artificial leaf" in
scientific studies of leaf boundary layer transport.
- As wind speed sensor and heat transfer
coefficient sensor in scientific studies at very low wind speeds.
Specifications
- Thermocouples: 40 Cu-CuNi
- Temperature range: -30 to +80 oC
- Sensor thickness (nominal): 0.15 mm
- Required readout: 2 diff voltage channels
1V and 5 mV range.
- Voltage input: 3 VDC (nominal)
- Interfacing: to most dataloggers
Options
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