Campbell Scientific Bowen Ratio Instrumentation - Manual (Page 12)

Section 2. Station Installation
2-2
Q7-BR
(system)
FIGURE 2-1. CSI Bowen Ratio System
2.2 Soil Thermocouples and Heat Flux Plates
The soil thermocouples and heat flux plates are typically installed as shown in
Figure 2.2-1. The TCAV parallels four thermocouples together to provide the
average temperature, as shown in Figure 2.2-2). It is constructed so two
thermocouples can be used to obtain the average temperature of the soil layer
above one heat flux plate and the other two above the second plate. The
thermocouple pairs may be up to two meters apart.
The location of the two heat flux plates/ thermocouples should be chosen to be
representative of the area under study. If the ground cover is extremely varied,
it may be necessary to have additional sensors to provide a valid average.
Use a shovel to cut a vertical slice in the soil and remove the soil to one side of
the cut. Try to keep the soil that is removed intact so that it can be replaced
with as little disruption as possible.
The sensors are installed in the undisturbed face. The depths are measured
from the top of the soil. A horizontal cut is made with a knife to install the
heat flux plate, and the stainless steel tubes on the ends of the thermocouple are
pressed in, keeping the tubes horizontal. When removing the thermocouples,
grip the tubing, not the thermocouple wire.