PGA460: PGA460 detect transducer disconnect

Hi user6060721,

To detect if the transducer has become disconnected or to check other abnormalities, use the built-in system diagnostic feature.

The system diagnostics include:

• transducer frequency measurement
• ring-decay time measurement
• excitation voltage measurement
• noise floor measurement

For example, highlighted are the system diagnostic results and settings of a working solution when using a 40kHz transducer in transformer driver mode:

In the case of the same settings where the transducer is disconnect, the highlighted results are:

Notice, in this failing/floating mode, the frequency diagnostic shows a much higher value, the decay time is much shorter, and the noise level increases.

You can use the system diagnostic frequency thresholds to quickly check all diagnostics in the diagnostic field byte when UART_DIAG=1.

user6060721,

The system diagnostic check can be performed whether the AGV is moving or not. Anytime you perform a burst-and-listen command to capture the time-of-flight result, the system diagnostic results also update in the background. So you can actually read the system diagnostic result (cmd 8) right after every ultrasonic measurement result (cmd 5).

user6060721,

The diagnostics are captured during burst and during the ring-decay as shown in figure 11 of the datasheet shown below, so it does not make a difference if an object is present or not. Please read section 7.3.5 System Diagnostics of the PGA460 datasheet for more details.

user6060721,

Situtation 2 offers a better result because the ultrasound energy only needs to travel one-way, rather than make a round-trip (double distance in situation 1). The ultrasound energy will be less attenuated in Situation 2. To achieve Situation 2, you must either:

• use a single PGA460 in the bi-static mode, which is one transducer connected to the driver block and another transducer connected to the receiver block. You can find an example of a bi-static PGA460 schematic here:
  • PGA460 Bi-static Transducer Transformer Driver Small Form Factor Design File
  • PGA460 Bi-static Transducer Half-Bridge Driver Small Form Factor Design File
• synchronize two independent PGA460 modules mono-static modules. This means placing one PGA460 device at point 1 and another and point 2. Here is an app note that describes the synchronization of two modules: 
  

  PGA460 Array of Ultrasonic Transducers for Triangulation and Tracking