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How to Use an Underground Anemometer

An anemometer is used by meteorologists to measure wind speed. In underground mining operations, an instrument known as a rotating vane anemometer measures the volume of air entering and exiting a mine. It assures that airflow in the mine is sufficient to prevent the accumulation and concentration of explosive gases. Although other methods of measuring air volume in mines are available, rotating vane anemometers have the advantages of being small, portable, safe for mine use, easy to maintain and relatively affordable. The standard method for taking a velocity measurement in a mine is to do a "traverse," or sweep, of a cross section of the air course.

Things You'll Need

Rotating vane anemometer
Extension handle
Stopwatch
Notebook and pen
Calculator
Calibration table

Instructions

Steps
- 1
  Determine the area of the traverse. If the area to be traversed is large, divide it in half. If the area has a high roof, divide it into four sections.
- 2
  Attach the anemometer to an extension handle to keep it away from your body, which minimizes the effect of air turbulence and allows you to reach high-ceilinged areas.
- 3
  Zero the anemometer dial and make sure the vanes are motionless.
- 4
  Place the anemometer at the corner of the traverse area where the air velocity is slowest, with the anemometer face perpendicular to the air flow on the downstream side.
- 5
  Allow the anemometer to reach full speed. Then simultaneously begin timing, release the vanes and begin the traverse. The participation of two people, one to operate the stopwatch and one to perform the traverse, is preferable.
- 6
  Use a steady, controlled up-and-down motion to sweep the entire area of the cross section, from one side to the other, for a period of 60 seconds or until the traverse is complete.
- 7
  Stop the stopwatch and the vanes simultaneously. Record the anemometer reading and the elapsed time.
- 8
  Repeat the traverse until you have two readings that are within 5 percent of one another.
- 9
  Repeat steps 2 through 8 for each section of a divided traverse.
- 10
  Divide the anemometer reading, which records feet, by the number of minutes the traverse took. For example, if the anemometer reading is 545 and the time of the traverse is 60 seconds, divide 545 by 1. The answer, 545, is the velocity in feet per minute, or fpm. If the stopwatch reading is not exactly 60 seconds, convert the seconds to minutes. For example, convert 75 seconds to minutes by dividing 75 by 60, which equals 1.25 minutes. Then divide 545 by 1.25, which gives you a velocity of 436fpm.
- 11
  Use the calibration table that comes with the anemometer, or the correction table created at the anemometer's latest calibration, to find the velocity correction. Find the velocity you have calculated on the correction table and add or subtract the listed correction factor. If the exact value of your calculation is not listed on the table, interpolate between listed values to estimate what the correction should be.
- 12
  Average the values of all the sections of a divided traverse to obtain the velocity of the entire cross section.

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