The assembled circuit board has to be posi- tioned such that the wind can reach it from all directions. To protect the circuit board from the elements it is best to fit it in an enclosure and mount the combination of T1/T2 a little higher so that they will protrude above the enclosure (seal the hole with silicone sealant). A good sensitivity is obtained when you set the temperature of T2 about 5 degrees above the ambient temperature. This is done by set- ting the quiescent current through T1, while there is no wind, to about 5 mA with the aid of P1. The reading on the meter is then marked as ‘calm’ (you can optionally change the meter scale as appropriate).

You may have to experiment somewhat with the value of resistor R1, so that the current through T1 cannot become too large. In case the circuit has some unstable tendencies (reacts too quickly to changes or overshoots on the meter), then the gain can be reduced by increasing the value of R5.
The circuit does not, of course, give exact val- ues, but is handy for detecting whether the wind blows a little, average, hard or very hard.



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