4.5 Sampling Rates

The recommended sampling rate for a digital data acquisition system depends on the end use of the data. Substantial evidence and experience suggest that 360 data values evenly spaced during the sampling interval will provide estimates of the standard deviation to within 5 or 10% [3]. Estimates of the mean should be based on at least 60 samples to obtain a similar level of accuracy. Sometimes fewer samples will perform as well, but no general guide can be given for identifying these cases before sampling; in some cases, more frequent sampling may be required. If single-pass processing (as described in Section 6.2.1) is used to compute the mean scalar wind direction, then the output from the wind direction sensor (wind vane) should be sampled at least once per second to insure that consecutive values do not differ by more than 180 degrees.

The sampling rate for multi point analog recorders should be at least once per minute. Chart speeds should be selected to permit adequate resolution of the data to achieve the system accuracies recommended in Section 5.1. The recommended sampling rates are minimum values; the accuracy of the data will generally be improved by increasing the sampling rate.

4. METEOROLOGICAL DATA RECORDING
 4.1 Signal Conditioning 
 4.2 Recording Mechanisms 
 4.3 Analog-to-Digital Conversion 
 4.4 Data Communication 
 4.5 Sampling Rates 
 4.6 Recommendations