Apparatus and calibration method for cup anemometers having non-removable cupsets
An apparatus and method is disclosed for calibrating a cup anemometer having a non-removable cupset. The calibration method may include mechanically connecting a cups assembly hub of the anemometer to a rotatable shaft of a variable-speed motor, placing at least the anemometer under vacuum so that drag effects on the cups assembly hub of the anemometer are eliminated when driven by the variable-speed motor, controlling the variable-speed motor to drive the cups assembly hub of the anemometer at a number of different rotational speeds, recording electrical signals produced by the anemometer at each of the number of different rotational speeds, and generating calibration data for the anemometer based on the recorded electrical signals and on expected wind speed values at each of the number of different rotational speeds.
1. An apparatus for generating calibration data for a cup anemometer having a non-removable cupset, the apparatus comprising:
an airtight enclosure,
a variable-speed motor positioned within the enclosure,
a mounting assembly positioned within the enclosure and supporting the variable-speed motor,
a flexible connector positioned within the enclosure and connected between a rotatable shaft of the variable-speed motor and a cups assembly hub of the anemometer,
a signal receiving meter positioned outside of the enclosure and electrically connected to a signal producing output of the anemometer, and
a vacuum pump configured to establish a vacuum within the enclosure so that drag effects on the cups assembly hub of the anemometer are eliminated when driven by the variable-speed motor.
2. The apparatus of claim 1 further comprising a variable-speed motor controller positioned outside of the enclosure and electrically connected to the variable-speed motor, the controller configured to selectively control rotational speed of the variable-speed motor.
3. The apparatus of claim 1 wherein the anemometer is configured to produce an output frequency signal proportional to rotational rate of the cups assembly hub.
4. The apparatus of claim 3 wherein signal receiving meter is a frequency meter.
5. The apparatus of claim 1 further comprising a processor configured to control operation of the variable speed motor controller and to capture output signals produced by the anemometer.
6. The apparatus of claim 2 wherein the anemometer is configured to produce an output frequency signal proportional to rotational rate of the cups assembly hub.
7. The apparatus of claim 2 further comprising a processor configured to control operation of the variable speed motor controller and to capture output signals produced by the anemometer.
8. A method for calibrating a cup anemometer having a non-removable cupset, the method comprising:
mechanically connecting a cups assembly hub of the anemometer to a rotatable shaft of a variable-speed motor,
placing at least the anemometer under vacuum so that drag effects on the cups assembly hub of the anemometer are eliminated when driven by the variable-speed motor,
controlling the variable-speed motor to drive the cups assembly hub of the anemometer at a number of different rotational speeds,
recording electrical signals produced by the anemometer at each of the number of different rotational speeds, and
generating calibration data for the anemometer based on the recorded electrical signals and on expected wind speed values at each of the number of different rotational speeds.
9. The method of claim 8 further comprising mechanically connecting the cups assembly hub of the anemometer to the rotatable shaft of a variable-speed motor via a flexible connector.
10. The method of claim 9 further comprising placing a combination of the variable speed motor and the anemometer under vacuum.
11. The method of claim 10 wherein placing a combination of the variable speed motor and the anemometer under vacuum comprises placing the combination of the variable speed motor and the anemometer in an air-tight enclosure, fluidly coupling a vacuum pump to the air-tight enclosure and controlling the vacuum pump to establish the vacuum within the airtight enclosure.
12. The method of claim 8 wherein controlling the variable-speed motor to drive the cups assembly hub of the anemometer at a number of different rotational speeds comprises controlling the variable-speed motor to drive the cups assembly hub at each of the number of different rotational speeds for a predefined time period before driving the cups assembly hub at a next one of the number of different rotational speeds.
13. The method of claim 8 wherein recording electrical signals produced by the anemometer at each of the number of different rotational speeds comprises recording the electrical signals produced by the anemometer for a predetermined time period at each of the number of different rotational speeds.
14. The method of claim 8 wherein the electrical signals produced by the anemometer are frequency signals corresponding to rates of rotation of the cups assembly hub of the anemometer.
15. The method of claim 8 wherein generating calibration data for the anemometer comprises:
determining a transfer function of the anemometer,
computing the expected wind speed values for each of the number of different rotational speeds according to the transfer function of the anemometer,
computing observed wind speed values from the recorded electrical signals produced by the anemometer for each of the number of different rotational speeds according to the transfer function of the anemometer, and
performing a regression analysis on the expected and observed wind speed values.
16. The method of claim 15 wherein generating calibration data for the anemometer further comprises computing calibration-corrected observed wind speed values based on the observed wind speed values and on data produced by the regression analysis.
17. The method of claim 16 wherein generating calibration data for the anemometer further comprises determining that the calibration-corrected observed wind speed values are acceptable if the calibration-corrected observed wind speed values deviate from corresponding ones of the expected wind speed values by less than a predefined deviation value.
18. The method of claim 8 further comprising placing a combination of the variable speed motor and the anemometer under vacuum.
19. The method of claim 18 wherein placing a combination of the variable speed motor and the anemometer under vacuum comprises placing the combination of the variable speed motor and the anemometer in an air-tight enclosure, fluidly coupling a vacuum pump to the air-tight enclosure and controlling the vacuum pump to establish the vacuum within the airtight enclosure.
20. The method of claim 9 wherein generating calibration data for the anemometer comprises:
determining a transfer function of the anemometer,
computing the expected wind speed values for each of the number of different rotational speeds according to the transfer function of the anemometer,
computing observed wind speed values from the recorded electrical signals produced by the anemometer for each of the number of different rotational speeds according to the transfer function of the anemometer, and
performing a regression analysis on the expected and observed wind speed values.