I'm working on an ultrasonic ranger (40kHz) and struggling with acoustic crosstalk between the transmitter and the receiver. With extensive use of the oscilloscope I discovered that during the first 100µs and with a value of 40k for the Rb resistor (see circuit diagram) the target detection is considerably larger then the acoustic crosstalk. The comparator can easily detect this difference.
Unfortunately, a 40k resistor limits target detection to short distances. However, longer distance detection can be archived if I increase the value of the Rb resistor by stages to 1M .
Appropriate values for Rb:
40k for the first 100µs
85k for the second 100µs
200k for the third 100µs
450k for the fourth 100µs
1M after 400µs
Does anyone have a suggestion of how to implement the resistor switching?
Thanks
Unfortunately, a 40k resistor limits target detection to short distances. However, longer distance detection can be archived if I increase the value of the Rb resistor by stages to 1M .
Appropriate values for Rb:
40k for the first 100µs
85k for the second 100µs
200k for the third 100µs
450k for the fourth 100µs
1M after 400µs
Does anyone have a suggestion of how to implement the resistor switching?
Thanks
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