Campbell Scientific BlackGlobe Temperature Sensor for Heat Stress - Manual (Page 14)

BlackGlobe Temperature Sensor for Heat Stress
TABLE 7-1. Wiring Diagram for Campbell Scientific Dataloggers
Color
Description CR800
CR850
CR5000
CR3000
CR1000
CR9000(X)
CR510
CR500
CR10(X)
21X
CR7
CR23X
Black Voltage
Excitation
Switched
Voltage
Excitation Switched
Excitation Switched
Excitation
Red Temperature
Signal
Single-Ended
Input Single-Ended
Input Single-Ended
Input
Purple Signal Ground AG
Clear Shield G
7.2 Calculations
7.2.1 Wet-Bulb Globe Thermometer Index (WBGT)
To calculate the WBGT index, a measurement of the BlackGlobe (radiant
heat), wet-bulb (evaporative heat), and ambient air (dry-bulb) temperatures are
required (Equation 1). In the approach discussed here, air temperature and
relative humidity measurements are used to calculate the actual vapor pressure,
and a dewpoint temperature is used to calculate the wet-bulb temperature.
Air temperature and relative humidity (%) measurements required for this
calculation can be made by a variety of sensors. In the examples shown in
Section 7.3, Programming, the HC2S3 is used.
Ultimately,
WBGT = (0.2 × BlackGlobe Temp) + (0.7 × Wet-Bulb Temp) + (0.1 × Dry-
Bulb Temp) (1)
Dewpoint and Wet-Bulb temperature units include: °C, °F, °K
7.2.2 Dewpoint
Equation 2 is used to calculate dewpoint.
T
d
= (241.88*ln(P/0.61078))/(17.558-ln(P/0.61078)) (2)
where
T
d
= dewpoint (°C)
P = vapor pressure (kPa)
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