Ultrasonic Receiver Circuit

Hi! Im currently working on my study regarding ultrasonic-based distance measurement device. I have a separate transmitter and receiver transducer.

I have built these circuits for the transmitter and receiver side similar to Mr. Kwong’s work (kerrywong.com/2011/01/22/a-sensitive-diy-ultrasonic-range-sensor/), but with some modification in the rc values at the receiver side like what he indicated in the comment section:
(6.8n, 1.2k → 1n 4k
0.1u, 1.2k → 0.1u 4k)

My transmitter side works, and outputs just the same figure he has shown in his website. The receiver, on the other hand, is my problem. I tried building the receiver circuit and get the distance readings but the results are very much inaccurate.

Could you please help me troubleshoot this? It will a a very big help for me if you would. Thanks in advance! :slight_smile:

Please do not double post. This wastes everyone's time.