Ping))) sensor

abecedarian

Has anyone done any studies into the efficacy of mounting the transducers side-by-side versus vertical? It seems to me that if they shared the same vertical axis, they'd be better at detecting smaller vertical objects in front of them like table and chair legs.



Please don't chastise me too much.

Hal Albach

As best as I can tell it should not make much, if any, difference since the transmitter is round in shape and the chirp it puts out will be cone shaped. You can find out for yourself by using one of the sample programs that continuously displays the Ping result and with both vertical and horizontal orientations place small object (maybe suspended from a string on a stick) in various locations to see what kind of readings you get.

abecedarian

I understand, that in theory, and if facing in the direction of a flat object, that as the sensor may pivot left / right, the TX and RX will approach / recede proportionally so the net echo delay shouldn't change.


What I'm curious about is more like how the echoes would be different:

|
TX >           |
           O   |   <- this is a wall
RX <           |
               |

... versus...

|
               |
T/RX ><   O    |   (TX / RX transducers vertical)
               |
               |

If off-center, would the former or latter be more likely to detect the obstruction?

Hal Albach

I am wondering if you think that the Ping uses both transducers to send and receive the ping and echo. That is not the case, One transducer sends out the chirp and the other transducer listens for the echo, after a very slight delay. Operating the Ping with the transducers one over the other or side by side should not alter the way the unit perceives the echo.
Now, if you are panning the Ping back and forth, a long thin object lying horizontal will reflect more echos back than if that same object were standing vertical. That is the object's orientation to the sweep, not the orientation to the Ping. Whether the Ping was mounted horizontally or vertically you should see the same echo values during the sweep.

Duane Degn

I imagine there are times when the orientation of the transducers with respect to an obstacle would affect the strength of an echo but I'd be surprised if this difference were easy to measure.

Many Sharp IR distance sensors have a very asymmetrical detection zone. I've read several sources which suggest orienting Sharp IR sensors vertically rather than horizontally.

I mounted both the IR and Ping sensors in a vertical orientation on my robot used to test the Eddie firmware.



I mounted the Ping sensors vertically in order to keep them close to the IR sensors.

abecedarian

I suppose I should say I work in the cellular/wireless/mobile communications industry. We often have to deal with, and correct for, multipath distortion.
The effects at RF frequencies would probably be more pronounced than when compared to near audible frequencie

prof_braino

If I recall, the parallax offset from the emitter and detector is not so significant in the range of the senosr, that is, farther than 3 cm(?).

I think a bigger influence is how close the target is to other "noise" targets. For example, if the sensor is closer to the floor, more of the floor falls within the "chirp cone", which means the floor can cause readings that are "too close". This also applies to IR sensors. Its really all about "what else lies in the senor's 'chirp cone'?"

Phil Pilgrim (PhiPi)

If the transmit and receive transducers were far apart relative to the subject distance (which they are not), you might be able to detect a difference due to orientation. Thin objects aligned parallel to the line between the two transducers would produce a stronger echo than those aligned perpendicular. But in the Ping))) the transducers are too close together for this to have a measurable effect.

-Phil

abecedarian

Thanks to all who have replied.

I think I'm going to get the sensor and do some experimentation, and graph some results.