Massa M3 Manuale Utente Scaricare il pdf (Pagina 6)

Instruction Guide – Massa M3 Wireless Sensor Evaluation Kit Page of 14

M3 Kit Guide 111017.docx 10-20-2011

PRELIMINARY

M3 Application Software

Understanding the Ultrasonic Waveform

The ultrasonic waveform is a very important tool, particularly when diagnosing problematic

applications. A typical ultrasonic waveform is shown in the figure below. The waveform can be

divided into three sections. The first pulse on the left is from the Sensor’s ping, or transmit pulse,

when the sound wave is transmitted. This is followed by a reflection from the liquid surface, which is

the pulse to the right of the transmit pulse in the figure. The Sensor is designed to ignore the

transmit pulse and detect the first reflected signal that exceeds the detection threshold, and then

calculates the range to the liquid surface. The red line shown in the waveform represents the

detection threshold level. Other reflections that follow are ignored.

Ideally the acoustic path between the M3 Sensor and the liquid surface is clear of targets that can

cause detectable reflections. These reflections could be caused by items such as ladders in the tank,

the side of the tank if the Sensor is mounted too close to the edge of the tank, or by the Sensor not

having been installed level, which would cause the sound beam to not be perpendicular to the

surface of the liquid. In more difficult applications, adjustments to the Sensor’s sensitivity could

provide a solution, but before attempting to utilize this feature, consult with Massa Products for

support. As you shown in the waveform below, the first reflection, which is from the liquid surface, is

approximately 60 inches from the Sensor and there are no targets in the sound path.

If the Sensor, when operating at high gain and the maximum number of transmit cycles, does not

have a reliable reflection that crosses the detection threshold when the liquid is at its lowest

expected level, then it may be necessary to use a Sensor with a longer range. Consult with Massa

Products for more information.

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Massa M3 Manuale Utente Pagina 6