# Biomedical Engineering - Amplifier

According to the book, the main use of thermal-velocity sensors is to measure the velocity of blood. So, it's plausible that there is a relation between the "obvious" and a blood velocity somewhere in the neighborhood of RT.

## Homework Statement

I- What is application of this circuit? What does it do?
II- Simulate this circuit in a simulator software and by determine correct values for resistors, show heat losses (H) is nearly constant.
III- Calculate H analytically (manually) (voltage division) and compare with part II in a software.
Hint:
(Comparator)
IV- By proper ratio selection for resistors, show sensitivity of heat losses (H) with respect to thermal resistance (RT) is almost zero.

## The Attempt at a Solution

I- What is application of this circuit? What does it do?
Look at the schematic in part 1 of the problem statement and at least tell us this much.

Bystander said:
Look at the schematic in part 1 of the problem statement and at least tell us this much.
I only know this circuit is from Book "Medical Instrumentation Application and Design (by John G. Webster)"

I only know this circuit is from Book "Medical Instrumentation Application and Design (by John G. Webster)"
Hint: the purpose of the circuit is written in the first figure.

CWatters
@Paradoxs -- Per the PF rules, you must show some effort before we can offer tutorial help. Please post your thoughts on this problem.

berkeman said:
@Paradoxs -- Per the PF rules, you must show some effort before we can offer tutorial help. Please post your thoughts on this problem.
The circuit (part 1) is Thermal velocity meter circuit
according to Book "Medical Instrumentation Application and Design (by John G. Webster) - 4th edition - Page 383" The main use of thermal-velocity sensors is to measure the velocity of blood and to compile velocity profiles in studies of animals, although such sensors have also been regularly used to measure velocity and acceleration of blood at the aortic root in human patients undergoing diagnostic catheterization.
I simulate the circuit in Proteus:

Nice tool. Now for understanding of what's going on in the circuit. You familiar with Ohm's law ? Can you express VA/V0 in an expression with Rx and R1 ? Idem VB/V0 in an expression with RT and R2 ?

 initially assuming there is no current going into the operational amplifier, that is.

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