Help with sensor measurement using signal conditioning

Thread Starter

redboot92

Joined Nov 30, 2020
3
Hello everyone,

I am working on a sensor measurement using signal conditioning circuit which consists of measurement circuit (U1), signal amplification (U2), and absolute value circuit (U3 and U4). What im asking from this community is to help me check and correct my understanding the signal conditioning circuit design that have been pass down from one student to another student and now to me.

This is my understanding: ( please help me confirming my understanding)
1. what matter in amplifier circuit is the gain and its infinity value that has to be controlled using feedback resistor (R2 and R8).
2. feedback capacitance C4, C8, and C9 is used to block DC voltage and to allow varying signal.
3. i read somewhere, there is low pass filter stage consist of RC passive stage before signal amplification (U2). Im guessing R7 and C7 is the low pass filter. but since R3 and C5 and R16 and C6 have the same values as R7 and Ct , respectively, im guessing they all are low pass filter.
4. Op-amp U3 and U4 perform absolute value circuit, where the only thing im sure of is R11 feed the signal back to the non-inverting amplifier and R1 is the input resistor that controls the stage gain. . i don't know whats the purpose of R5 and R6 connected to the diodes. and i don't know what the purpose of U3.

Can anyone enlighten me please.... your knowledge is very much appreciated.
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Thread Starter

redboot92

Joined Nov 30, 2020
3
You're making this too easy. The Base Emitter voltage depends on the current. This voltage for the second transistor will be less than the third one by 120 mV. That's the voltage for the first transistor, which will be even lower. Also, the voltage on the first transistor may be greater than the power supply.

Hello sir, can you help me on this matter? the link is the post to my questions

https://forum.allaboutcircuits.com/...stand-the-signal-conditioning-circuit.174594/
 

Wolframore

Joined Jan 21, 2019
2,273
Please explain how this is being used and what do you mean student to student? Is this a school project or homework? Also if for class it depends on where you are in your study... for example what happens when you have 3 of the same active LPF? Did you cover this yet? If you did then you need to review your material, if you haven’t then let your professor do the work.
 
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