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Section 2: Installation
2.1 System Explanation
The Accutron airflow sensors are compact and reliable instruments, especially designed for measuring
airflows in mining environments. The Accutron IS Drift System is for airflow measurements in mine
drifts whereas the Accutron IS Fan System is for measuring the flow output of large mining fans. Each
system consists of an Indicating Transmitter, cabling and two “ultrasonic sensor” assemblies.
The ultrasonic sensor assemblies are installed in the drift diagonally (one further upstream than the
other) with an “imaginary line” between them intersecting the airflow at a typical angle of 120 degrees.
Ultrasonic pulses are sent back and forth between the transducers across the drift, traveling through the
air current. Let “T
A-B
” be the time taken for the signal to travel from Transducer A to Transducer B, and
“T
B-A
” be the time taken for the pulse to travel from Transducer B to A. The control unit accurately
measures the time-of-flight for each direction. The difference between the measured times (T
A-B
– T
B-A
)
is directly proportional to the airflow. In the case of no moving air, T
A-B
equals T
B-A
and there is no time
difference because there is no airflow.
The Accutron IS first internally computes the average velocity of the air in Meters/Sec. In order to
obtain air volumes, the area of the drift is entered into the settings menu (during programming), along
with your selection of measurement units. The system then displays air volumes in the units selected.
Common units used in mining applications are KCFM and M**3/S, other units may also be displayed to
measure the air velocity (Meters/ sec, Feet / Min).
After installation in the drift, measurements are made (area, baseline distance, Face-to-face distance).
Using the navigation buttons, these parameters are entered into the unit.
These parameters are retained in non-volatile Flash memory in the Accutron. Whenever the Accutron
powers up, this information is automatically reloaded.
The system can easily measure air velocities in excess of 1,000,000 cfm with a precision better than any
other conventional methods, as well as low velocity conditions (i.e., 1m/s). In addition, since the system
can sample across the entire drift, readings are more representative than “single point” measurements.
The Accutron considers that there is a “distribution profile” for the air in the drift, making it superior to
other types of measurement methods for fixed installations.
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