User manual

Hukseflux Thermal Sensors
HFP01SC Manual v0811 page 31/33
Sensor
specific
part,
entering
R
self
, R
cur
and A
self
,
possibly
also E
sen
.
This is typically done in the
data logger, but could also be
done in a later stage, during
processing.
The heater
resistance, A
self
and
E
sen
can be found on
the calibration
certificate.
Repetitive
loop
typically 3
or 6 hour
repetition.
Measure V
sen
(0)
Store V
sen
(0)
T
here usually will be
a significant signal
representing the
present heat flux at
that moment.
Temporarily stop the normal
soil heat flux measurement
Typically for 6
minutes, can also
be stoped for
longer.
Switch heater on
Measure the voltage across
the current sensing resistor
V
cur
Measure the steady state
sensor output V
sen
(180).
Store V
sen
(180).
Switch off the heater
Measure the steady state
sensor output V
sen
(360).
Store V
sen
(360).
Calculate the average of
V
sen
(0) and V
sen
(360).
This is to
compensate for
changes in soil heat
flux level.
Calculate the amplitude V
amp
.
Calculate the new sensor E
sen2
Do quality assurance tests
Start normal soil heat flux
measurement again using
E
sen2
Repeat either on user demand
or on a regular time schedule
Table 10.1 Typical ingredients of a program for measurement
and control of HFP01SC.