TDC1000-TDC7200EVM: How to perform liquid level sensing through the bottom of a metal tank

Hi Bharat,

I will make some tests today and I let you know ASAP.

Thanks for the tip!

Hi Bharat,

I bought a new metal tank with 300 mm of height and 200 mm of diameter, to improve the tests.

I did a lot of tests as you asked, changing the RX COUNT with this configuration, but none of the 7 options changed the result.
The STOP signal didn't happen either.

The image bellow is the COMP_IN (Yellow) with no stop signal (Blue).

After this test, I did some modifications:

• NUM_TX to 10;
• NUM_RX to 3;
• ECHO_QUAL_THLD to -125mV;
• CLOCKIN_DIV to 2;
• AUTOZERO_PERIOD to 128us;

Doing this I could to see the "stop signal" with the tank full of water.

I started to empty the tank with a rubber hose in a constant flow. The image bellow is the result.

As you can see, the measurement is not constant like the plastic cup.

In the oscilloscope, I can see a lot of stop signal, but changing fast in the time generating "spikes" in the graphic. If I increase the ECHO_QUAL_THLD to -220mV or higher, I not able to generate the stop signal again.

Thank you!

Regards,

Hi Bharat,

Do you have any news about this issue?
Thank you!

Hello Uilter,

Looks like the return Tx signal is week we can approach this through either of the 2 ways as below:

1. Try to increase the Tx voltage thorugh an external amplifier or provide the TDC1000 with a 5.5V (remember the Jumper JP3 in the EVM connects the VDD & AVDD, please remove this jumper & then connect a 5.5V to the VDD supply pin.

2. Also try a large dimension transducer.

please let me know if you need any further info in this regards, I will be happy to help you.

Hello Bharat,

I'll try both options to get a better result.

ASAP I'll return with the progress.

Thanks.

Hi Bharat,

The option 1 improved a litle the signal, but in high levels the signal have a lot of noise. This "noise" could be generated by a too low ECHO_QUAL_THLD?

The option 2 was the worst, I was able just to read 50% of the level, the rest I get a timeout. I tried this with a 25mm transducer.
Measuring the COMP_IN there is no signal at all. With large transducer I need to change any settings?

Thank you!