Campbell Scientific A100LK Anemometer - Manual (Page 14)

A100LK Anemometer
7.3 Programming with CRBasic and Edlog
Wind speed is typically measured using a pulse channel. For dataloggers using
CRBasic, use the PulseCount() instruction with the pulse channel configured
for high frequency with frequency counting. For dataloggers programmed with
Edlog, use Instruction 3 and for parameter 3 specify configuration code 22 to
output frequency in Hertz.
7.3.1 Slope and Offset Calculations
The slope value is entered as the multiplier in the pulse count instruction. For
the best accuracy you should always obtain an individual multi-point wind
speed calibration in a reputable wind tunnel (such as MEASNET) wherever the
highest accuracy results are required.
Calculations for a nominal A100LK suggest that the nominal figures for the
datalogger would be: slope = 0.0499, offset = 0.258 (for results in m/s, best fit
over 4 to 16 m/s) (ref 2).
However, slope/offset figures from Garrad Hassan quotes consensus figures for
the A100LK as: slope = 0.0499, offset = .2400.
The example programs contained in this manual use the calculated offset value.
7.3.2 Example Programs
Pulse Port Example
The following CR1000 example program uses a pulse port to measure the
A100LK-L once a second. The program stores the mean, maximum,
minimum, and standard deviation of the measured wind speed over a 10 minute
interval.
'CR1000 Series Datalogger
'Program to measure A100LK-L and store ten minute averages
'Wiring
'White ------- Signal ------- P1
'Red --------- Power -------- 12V
'Blue -------- Power Ground - G
'White ------- Shield -------
'Declarations
Const A100LK_L_mult = .0499
Const A100LK_L_offset = .258
Public PTemp, batt_volt
Public WS_ms
'Define Data Tables
DataTable (Test,1,1000)
DataInterval (0,10,Min,10)
Minimum (1,batt_volt,FP2,0,False)
Sample (1,PTemp,FP2)
Average (1,WS_ms,FP2,False)
Maximum (1,WS_ms,FP2,False,False)
Minimum (1,WS_ms,FP2,False,False)
StdDev (1,WS_ms,FP2,False)
EndTable
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