One interesting possibility not mentioned yet would be an AGC controlled amplifier that would try to hold the output level constant by adjusting the gain. Then the actual signal magnitude can be determined by watching the gain control voltage. That scheme is widely used in communication equipment and it works very well.

 

One interesting possibility not mentioned yet would be an AGC controlled amplifier that would try to hold the output level constant by adjusting the gain. Then the actual signal magnitude can be determined by watching the gain control voltage. That scheme is widely used in communication equipment and it works very well.

Sir I researched about TSR and AGC but eventually this setup was what I could made.

 

OK, I must have missed that post. Indeed, all concepts are subject to limits of resources.

 

Aside from being like this, I learn a lot and it is what I do this project for. I will apply some more tests.

 

Hi , I made this circuit and it seems working. I can upload a video tomorrow. I also bought LM393 , it's on delivery.
Can we discuss about the point I am at after I upload?

 

I could not upload because I broke it when I was trying to move the circuit to a bigger board.

 

Hi demi,
Just upload the circuit diagram and any simulation file for that circuit.
E

 

This is the last circuit setup I made.

 

Hi demi,
That TGC [ timed gain control ] is not going to work as required.

You require a swept variable gain, not a stepped gain.
After the end of TX output pulse, you require a suppression period, that is, the program ignores the TX piezo resonant decay pulses after the TX period.
Then the swept gain starts with a high attenuation level, which reduces at a linear or exponential rate, up to the time of maximum echo range.
E

 

I got what you mean as swept gain but could not find any other way to do that. Could you help a little bit more or give some hints on that subjective pls ?

 

Hi demi,
As you know I cannot post my working circuit, but this shows the plots.
1. V4 is the input to the Comparator, note how the signal stays the same amplitude but rides on a rising ramp voltage.
2. Vref is the other input to Comp
3. Vo is the final output.

4. Vin is the initial input from the piezo.

Hint: think P JFet for the attenuation circuit. eg 2n3820

E

 

Hi demi,
As you know I cannot post my working circuit, but this shows the plots.
1. V4 is the input to the Comparator, note how the signal stays the same amplitude but rides on a rising ramp voltage.
2. Vref is the other input to Comp
3. Vo is the final output.

4. Vin is the initial input from the piezo.

Hint: think P JFet for the attenuation circuit. eg 2n3820

E
View attachment 328043

Hi Eric , as looking onto your post , I guess like you have an increasing voltage x and summing our output with it. Than you comparate the output with vref. Is this correct or close ?
In this case I guess it is a different comparating technique but varying gain.

 

I changed circuit again , can you review it ?

 

LOOL IT WORKED HAHAHAHAHA

 

 

Hi demi,
As you know I cannot post my working circuit, but this shows the plots.
1. V4 is the input to the Comparator, note how the signal stays the same amplitude but rides on a rising ramp voltage.
2. Vref is the other input to Comp
3. Vo is the final output.

4. Vin is the initial input from the piezo.

Hint: think P JFet for the attenuation circuit. eg 2n3820

E
View attachment 328043

Btw I missread this and guessed the circuit so i am also happy bout this

 

Hi demi,
This is the limit on the help I can give on your assignment
This version maybe easier for you to follow.
The gain is set to a high value and then attenuated by the jFET in a controlled decreasing level of attenuation.

Work out a circuit and post your results.
Hint: You should have a trimmer potentiometer to set the Gain and Vref
E

 

Hi demi,
This is the limit on the help I can give on your assignment
This version maybe easier for you to follow.
The gain is set to a high value and then attenuated by the jFET in a controlled decreasing level of attenuation.

Work out a circuit and post your results.
Hint: You should have a trimmer potentiometer to set the Gain and Vref
E

Hi Eric , the circuit I posted seems working is there a problem with it ?

 

Hi demi,
Your scope images show the actual echo signal, do you have a scope photo of the comparator output, which should resemble a square wave?
E

 

Hi demi,
Your scope images show the actual echo signal, do you have a scope photo of the comparator output, which should resemble a square wave?
E

Hi sir , I willl make that stage today. Being able to set echo levels onto Vref without gaining the noise made me happy. I will upllad the comparator output. Btw now I have lm393 , may should I use that ?