Parking Sensor Detector alternative applications

Ask any questions about using PicoScope 6 Automotive software here.
Post Reply
Steve Smith
Pico Staff Member
Pico Staff Member
Posts: 1578
Joined: Sun Aug 25, 2013 7:22 am

Parking Sensor Detector alternative applications

Post by Steve Smith »

Recent usage of the Pico Ultrasonic Parking sensor detector https://www.picoauto.com/products/test- ... r-detector during parking sensor testing https://www.picoauto.com/library/automo ... g-sensors/ got me thinking about alternative uses for such a device tuned to 40 kHz (Ultrasound)

A number of vehicle alarm systems (O.E and Aftermarket) use such a frequency for interior motion detection and so using the PicoScope Spectrum Mode in conjunction with the Parking sensor detector, it is simply a case of placing the sensor inside the vehicle, arm the alarm system and wait for activity on the scope screen.

Sorry I should have mentioned, PicoScope Spectrum Mode is not “active” by default within the PicoScope Automotive software. Select Tools > Preferences > & Options to access a number of additional, invaluable features of PicoScope.
Set up
Set up
Tick the box adjacent to “Spectrum” in order to activate Spectrum mode, followed by Apply > OK Spectrum mode (Frequency based instrument) will now be available for selection at the top left hand corner of your screen.

“Frequency based” means the scope will display frequency along the X Axis rather than Time, and amplitude of the measured signal along the Y Axis. (Identical to our NVH Frequency View)
Frequency Mode
Frequency Mode
Using the parking sensor detector connected to channel A of PicoScope & placed inside the cabin of our VW T5 van (alarm armed) we can clearly see activity around 40 kHz, confirming our ultrasonic interior motion sensors to be operating. (See above scope screen)
Sensor inside cabin
Sensor inside cabin
An interesting bonus using this technique was the ability to monitor “settle time” as the ultrasonic motion sensors do not become active immediately after arming the vehicle. This varies depending on manufacturer but often ultrasonic activation coincides with a change of state from the vehicle Alarm LED. For example: LED reverts to slow flash from fast flash or solid LED to flash etc.

Given we can confirm ultrasonic activity, what about ultrasonic interior coverage?

Using the Reference Waveform feature of PicoScope, https://www.picoauto.com/library/traini ... and-tricks the captured amplitude of the ultrasonic signal in the cabin could be compared to the signal in the load space of our T5 van
Reference waveform
Reference waveform
The waveforms above measures the peak amplitude of our 40 kHz ultrasound signal within the cabin (adjacent to the driver) at -89.05 dBu (channel A Blue) and within the upper load space area (adjacent to the rear tail door) at -100.3 dBu (Magenta Reference waveform)

We can therefore conclude the ultrasonic coverage of the load space (whilst protected) the signal strength is much weaker than in the cabin.

This is no surprise given the vehicle ultrasonic transceiver is located within the cabin roof and the design of such interior movement detection may be characteristically biased away from the load space to prevent false alarms from insecure payloads.

Ironically, at the floor level of the vehicle load space there was zero ultrasonic activity detected!
Another reason for pursuing such a measurement was to utilize the vehicles ultrasonic motion sensors for the detection of wind noise.

Using the parking sensor detector on the outside of the vehicle with the alarm system armed (motion sensor active) would enable ultrasound at 40 kHz to be detected around leaking window and aperture seals. (Or so I thought)

Given the ultrasound motion sensors are designed to cover the interior of the vehicle at best, expecting a small aperture/window seal leak (sufficient to generate wind noise) to allow for the passage of ultrasound outside the vehicle was a “big ask”!

I guess with hindsight, this is no bad thing as the number of false alarms from these vehicles would increase tenfold as they age and seals begin to compress over time.

The T5 VW van under test has a known window seal weep sufficient to generate a nuisance wind noise a highway speeds. Using the parking sensor detector with the vehicle alarm system armed confirmed no leakage of ultrasound
Wind noise check
Wind noise check
Using a dedicated 40 kHz Squawker placed inside the cabin proved far more effective, delivering pin point ultrasound with sufficient clarity and amplitude to highlight cabin/window seal leakage using the parking sensor detector.
Squawker test
Squawker test
All in all, the above tests conclude the parking sensor detector to have alternative applications where we can confirm alarm ultrasound motion sensor activity, coverage, settle time and leakage (Where large cabin leakages exist. (In reality this would have to be a window left open!)

For detection of wind noise we used a superior dedicated squawker from an aftermarket Wind Noise Leak Detection Kit. These devices can also be obtained from pet stores, electronic suppliers or even “homemade” if time allows
VW T5 INTRUSION SENSOR MID CABIN.psdata
Spectrum Mode capture (Cabin Sensors)
(583.47 KiB) Downloaded 601 times
I hope this helps, take care……Steve

Post Reply