Campbell 110PV, Руководство по эксплуатации продукта, Страница: 23 / 34

The coefficients used for the Steinhart-Hart equation are:
A=1.129241 x 10
–3
B=2.341077 x 10
–4
C=8.775468 x 10
–8
8. Operation
This section discusses the following:
8.1 Measurement details 13
8.2 Electrical noisy environments 14
8.3 Long cable lengths 14
8.1 Measurement details
Understanding the details in this section is not necessary for general operation of the 110PV with
our data loggers.
Simple half bridge measurement, ignoring cable resistance, has a measured voltage, V, of:
V = V
x
(4990/(4990 + R
t
))
Where V
x
is the excitation voltage, 4990 ohms is the resistance of the fixed resistor and R
t
is the
resistance of the thermistor.
The resistance of the thermistor is:
R
t
= 4990((V
x
/V) - 1)
The Steinhart-Hart equation is used to calculate temperature from resistance:
T
C
= 1/(A + B(ln(R
T
)) +C(ln(R
T
))
3
) – 273.15
Where T
C
is the temperature in Celsius. The Steinhart-Hart coefficients used are:
A = 1.129241 x 10
–3
B = 2.341077 x 10
–4
C = 8.775468 x 10
–8
110PV Surface Temperature Probe 13