Sonic Tracker basics
The 9142 Topcon Sonic Tracker II sends sound pulses 39 times per second. The sound waves strike the reference (ground or stringline), and the echo is bounced back to the tracker. The Sonic Tracker measures how long it takes for the sound waves to return to determine the distance from the surface or reference.
Depending on the timing, the system will drive the hydraulic valves to maintain the set distance. This timing is set by the operator.
The working window makes the Sonic Tracker unique. The working window is an operational range .2' (1.5 cm) above and below the grade reference. As long as the reference falls within the working window, the system will send corrections to the control box to drive the hydraulics.
If the reference is outside of the working window, the tracker and the control box will display a slow flashing arrow indicating which way the tracker needs to move to put the reference back into the working window. In the No Grade Correction or outside the working window, no hydraulic corrections will be sent.
In this example, the reference (stringline) is within the course area of the working window, which would be indicated by a solid arrow on the tracker and control box. If the automatics are engaged, the control box would send a signal to the hydraulic cylinder to move the tracker up until the reference is in the On Grade section.
In the fine correction or flashing zone, the Sonic Tracker and control box would display a fast flashing arrow indicating that the tracker is within .05' (1.5 cm) of grade.
When the Sonic Tracker is On Grade, the tracker and control box will display a flashing On Grade arrow.
Think of the Sonic Tracker as having an internal stopwatch, as shown in the image. As long as the timing of the returning echoes fall within the range of the working window, hydraulic corrections will be sent to the hydraulic valve to keep the tracker On Grade.
In this example, stringline pins are used to support the elevated stringline, with the top of the pin being outside the working window. When the tracker sees the top of the pin, the reference is ignored, and no corrections are made. If the top of the pin was within the working window, the system would have tried to make a correction, leaving a bump in the grade.
The sonic footprint starts out about 2" in diameter and tapers out. At 24" (62 cm), the sonic footprint should be at least 6" (15.25 cm) or larger. Having a sonic footprint of less than 6" (15.25 cm) at a height of 24" (62 cm) indicates a problem with the sonic transducer, and it may need to be replaced.
The working range of the 9142 Sonic Tracker II is from 14" (35 cm) to 55" (140 cm).
When using the 9142 Sonic Tracker II for paving or milling applications to follow existing or new asphalt, the ideal distance is approximately 18". Also be sure when using the tracker for paving or milling applications to have a temperature bail installed to compensate for dramatic temperature changes.