1.
Introduction and General Theory
HFP01 is the world’s most popular sensor for heat flux measurement in the soil,
through walls and building envelopes. By using a ceramic-plastic composite body
the total thermal resistance is kept small.
HFP01 serves to measure the heat that flows through the object in which it is
incorporated or on which it is mounted. The actual sensor in HFP01 is a thermopile.
This thermopile measures the differential temperature across the ceramics-plastic
composite body of HFP01. Working completely passively, HFP01 generates a small
output voltage proportional to the local heat flux.
Using HFP01 is easy. For readout one only needs an accurate voltmeter that works in
the millivolt range. To calculate the heat flux, the voltage must be divided by the
sensitivity; a constant that is supplied with each individual instrument.
HFP01 can be used for in-situ measurement of building envelope thermal resistance
(R-value) and thermal transmittance (H-value) according to ISO 9869, ASTM C1046
and ASTM 1155 standards. Traceability of calibration is to the “guarded hot plate”
of National Physical Laboratory (NPL) of the UK, according to ISO 8302 and ASTM
C177.
A typical measurement location is equipped with 2 sensors for good spatial
averaging. If necessary two sensors can be put in series, creating a single output
signal.
If measuring in soil and a more accurate measurement is needed, the model
HFP01SC should be considered.
If a more sensitive measurement is required, model HFP03 should be considered.
In case of special requirements, like high temperature limits, smaller size or flexibility
the PU series could offer a solution.
This manual can also be used for HFP03. Differences between HFP03 and HFP01 are
highlighted in a special appendix on HFP03.
Enabling better research outcomes in soil, plant & environmental monitoring.
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