TDC1000-Q1: Using Non-contact transducers with TDC1000

Hi Sujith,

The main disadvantage with measuring ultrasonic through air is that the speed of sound is significantly lower in air (300m/s) compared to fluids (1400m/s in water) and thus the attenuation through the medium is much greater. As a result, the transducer will require much more power to receive a return echo at reasonable distances.

What is the application? What kind of distances are being measured?

Regards,

Thank you, Scott, for the valuable information.
My application is to measure water level in a reservoir. I was searching for modules which cover a better range (6-8 meters) and with low power usage compared to custom built circuits. Also, I would like to integrate a communication module such as Bluetooth along with it.
Do you have any suggestions which suit best for this application?

Hello,

Since the maximum measurement time for the TDC1000 is 8ms, you will be limited to about 5.5m of distance in water. For measuring through air, the PGA460 will be a better fit, and it is capable of measuring in the 6-8m range. I am notifying my colleague of this, and he can help if you have any questions regarding the PGA460.

Regards,

Sujith,
The PGA460 was designed for ultrasonic time-of-flight based measurements through air. The integrated record timer allows for a maximum detectable range of approximately 11m, so your range requirement is optimal. I would recommend a low-frequency transducer (40-80kHz) with a wide beam pattern, such as the SensComp 40KPT25 (Prowave 400EP250). This type of transducer focuses the majority of the transmit energy in the forward facing direction (no side lobes) to maximize returns from the surface of the water. In addition, the closed-top nature creates a hermetically sealed sensor to protect from water/dust.

I recommend that you evaluate the PGA460 using the PGA460-Q1 EVM available at: www.ti.com/.../BOOSTXL-PGA460
The EVM includes two transducers. The included Murata MA58MF14-7N was designed for automotive applications, but can still give you an idea of the type of ranging performance and transformer driving requirement you can expect from a closed-top transducer.

For a complete listing of compatible transducers, see the PGA460: Air-Coupled Ultrasonic Transducers & Transformers Listing at: e2e.ti.com/.../620399

Akeem,

Thank you for your valuable reply. I also got a suggestion about  PGA450-Q1 from one of my colleague.

Can you tell me the advantages of using PGA460 over PGA450? SInce PGA450 have an Integrated Microcontroller in its core I would like to prefer it.

If I'm using PGA460, I need to add an extra microcontroller unit such as MSP430FR5959 with it right? In actual field results, which is system will be better in terms of power consumption and size, PGA450 or PGA460?

Thank you Scott

Sujith,

The PGA450 and PGA460 are both fully integrated ultrasonic sensor drivers and signal processors. The main difference is that the PGA450 has an integrated 8051 MCU, and the PGA460 has an integrated digital state machine. This means that the PGA450 can be customized to execute more than a time-of-flight to distance conversion. However, since both devices were intended primarily (almost exclusively) for time-of-flight to distance conversions, the additional programability of the PGA450 may not be necessary. For most applications, the code that needs to be programmed in the PGA450 usually ends up being identical to what is already offered as a built-in commands of the PGA460. The PGA460 relieves the user from the burden of having to develop/program code for the IC itself. The user is only required to optimize the EEPROM register settings accessed by the built-in PGA460 digital state machine commands.

These devices are intended to be used as slave nodes, so either would need a master controller (i.e. automotive ECU for park assist application). The PGA450 can be programmed to act as a limited master due to its integrated 8051, but unless your system is a localized and does not require any additional post time-of-flight actions, it is more than likely a separate MCU will be required for the PGA450 as well. Are you trying to fit the Bluetooth stack within the PGA450's integrated 8051? Note that you have a total of 8kByte OTP memory available in the PGA450; consider the time-of-flight code to consume about 1-2kByte of this memory.

Other than measuring distance, would your system do anything else with the time-of-flight data? If not, then I highly recommend the PGA460. If you are trying to build a BLE-wireless ultrasonic module to measure the liquid level in the tank, perhaps the PGA460 + CC2640R2F combination would be the best fit.

The PGA460 is superior in every aspect of performance (max single record range of 11m instead of 7m), power consumption (offers 300uA low-power mode), size (TSSOP16 instead of TSSOP28), and cost ($1.65 instead of $2.60 at 1k units).