Connect the test leads of a digital voltmeter across the resistor to measure the plc lo.9 current. The measured wind speed and direction at several cardinal calibration points should correspond to the following:
Wind Direction | | Wind Speed (mph) | | Loop Current | (mA) | V 1000 (Volts) |
N+ | | 0.0 | | 4.0 | | 0.4 |
NE = 45 ” | | 12.5 | | 6.0 | | 0.6 |
E = 90 ” | | 25 | | 8.0 | | 0.8 |
SE = 135 ” | | 37.5 | | 10.0 | | 1.0 |
S = 180 ” | | 50 | | 12.0 | | 1.2 |
SW = 225 ” | I | 62.5 | I | 14.0 | I | 1.4 |
W = 270” | | 75 | | 16.0 | | 1.6 |
NW = 315” | I | 87.5 | I | 18.0 | I | 1.8 |
N - | 100 | 20 . 0 | 2.0 |
5.1 Circuit Board Adjustments
Multiple turn potentiometers on the printed circuit board are provided for independent gain and offset adjustment of both the speed and direction channels as follows:
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The WMS-22 normally should not require adjustment of these controls. An exception occurs if for any reason the wind sensor is changed or if the cabling to the wind sensor exceeds 200 feet in length. In these cases the span control of the direction channel may require a slight adjustment. A movable jumper is included on the PC board direction channel to facilitate checking its offset and span adjustments. To use this feature, remove the jumper normally in place at the “JW” position and move it to the “JO” position. This should force the wind direction loop current to its zero scale or 4 mA level. If necessary, adjust R-25 to obtain this value, noting that counterclockwise rotation of its adjustment screw will cause the offset value to increase. Moving the jumper position to the “JF” location will cause the loop current to its full scale value of 20 mA. If necessary, adjust R-24 to obtain this value noting that counterclockwise rotation of its adjustment screw will cause an increase in the span. If either the span or offset trim are changed, it is suggested that both values be checked, since there is some slight interaction between the two adjustments. Be sure to return the jumper to the JW position at the conclusion of this adjustment procedure.
The Wind Speed channel should not normally require adjustment in the field.
