METER SC-1 User Manual

32
SYSTEM
so:
Equation17
g
s
=
ρ
!
D
vapor
e
s
(T
a1
)(1− h
r1
)
⎡
⎣
⎤
⎦
d
2
h
r1
e
s
(T
a1
) − h
r 2
e
s
(T
a2
)
− d
1
Therefore, g
s
is a function of the distances between RH sensors, temperature, and the two
RHreadings.
When the conductance is small, the humidities are nearly the same, and the denominator of
the denominator of Equation18 goes to 0, causing problems. Multiplying top and bottom by
the denominator gives
Equation18
g
s
=
ρ
!
D
vapor
h
r1
e
s
(T
a1
) − h
r 2
e
s
(T
a2
)
⎡
⎣
⎤
⎦
e
s
(T
a1
)(1− h
r1
)
⎡
⎣
⎤
⎦
d
2
− h
r1
e
s
(T
a1
) − h
r 2
e
s
(T
a2
)
⎡
⎣
⎤
⎦
d
1
NOTE: The resulting g
s
is in units of mol/m
2
s.
For this theory to accurately predict the stomatal conductance using the steady-state
diffusion technique, true steady-state conditions must exist in the diffusion path.
The amount of time necessary to reach steady-state conditions is proportional to the
conductance. At conductances <20 mmol/(m
2
s), steady-state conditions are generally
reached in <5 min. At higher conductances, steady-state conditions can take up to 30 min
and can become inaccurate.

METER SC-1 Specifications

General

Brand	METER
Model	SC-1
Category	Measuring Instruments
Language	English