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I would like to use an ultrasonic transmitter and three receivers to be able to determine the position of the transmitter relative to the receivers. The distances to be measured are around 3-4 ft. I want to understand how the receivers orientation relative to the transmitter can affect the distance measurement. I attach some simple pictures for illustration, in the first one the receiver is placed directly in front of the transmitter and opposite which is the ideal situation. In the second picture the receiver is placed in front of the transmitter but it is facing away from it. In the third picture the receiver is within the beam angle but is facing almost tangent to the beam. Basically as long as the receiver is within the beam range does its orientation matter?

receiver directly in front and facing transmitter

receiver directly in front and facing away from transmitter

receiver directly within beam angle and not directly facing transmitter

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As long as the receivers hear the signal clearly enough so that you can measure the time differential between those 3 receivers, it should be ok.

The orientation of the receiver affects the level of the received signal, not its timing.

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    \$\begingroup\$ If the receiver is highly directional, it may miss the direct wave and instead pick up a strong reflection off of something behind it, if that arrives in its most sensitive direction. \$\endgroup\$ – Chris Stratton Nov 3 '14 at 5:16
  • \$\begingroup\$ @Chris, that's true. And in any case, the receiver must consider the first signal received, not the strongest. On another note, it puzzles me how people seem to consider such complex signaling schemes for the ultrasound. I mean, we're doing it by just using plain digital signals, sometimes using hardware such as synchronous serial ports to generate them. Sorry that I can't go into more details, just something to think about. \$\endgroup\$ – PkP Nov 3 '14 at 5:22
  • \$\begingroup\$ Answer: noise immunity, if needed, requires complexity. You could think of that being mostly a receive problem, but it's not clear that a simple click is the ideal transmit waveform either. \$\endgroup\$ – Chris Stratton Nov 3 '14 at 5:28

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