MONITORING STATION INSTRUMENTATION AND MEASUREMENTS - Wind Resource Assessment: A Practical Guide to Developing a Wind Project - page 46

accuracy instruments are quite expensive, and as a result, most resource assessment
programs do not measure barometric pressure, instead they rely either on temperature
and elevation alone or on pressure readings from a regional weather station. Under
most conditions, both methods can yield acceptable accuracy. The main exception is
projects at especially high elevations (such as

2000 m above sea level) and with
no nearby weather station at a similar altitude, where it is recommended that high
accuracy air pressure measurements be taken.
Several barometric pressure sensors, or barometers, are commercially available
(Fig. 4-7). Most models use a piezoelectric transducer that sends a DC voltage to a
data logger and may require an external power source. Consult with the data logger
manufacturer to determine a compatible sensor model. Note that the transducer needs
to be exposed to the ambient outside air pressure. It must not be mounted in an airtight
enclosure or in a way that wind flow around the inlet could induce pressure changes.

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4.2.5 Relative Humidity
Since the amount of water vapor in the air affects its density, the use of a relative
humidity sensor can improve the accuracy of air density estimates. However, the
humidity effect is usually small, so this parameter is rarely measured for this purpose.
In cold climates, a relative humidity sensor is sometimes used for icing analysis.

Figure 4-7. A barometric pressure sensor. Source: Campbell Scientific.