# (wheatstone bridge) Pressure stimulation

Discussion in 'General Electronics Discussion' started by ykho21, Feb 4, 2012.

1. ### ykho21

3
0
Feb 4, 2012
Good day,

I'm a new member here. I am planning to make a small project which used to stimulate the pressure without the pressure gauge. This is a wheatstone bridge gauge with 1Kohm resistance each leg. Please refer to the picture.

How can I built a circuit that have a mV output? The Ex in is 5V.

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2. ### Harald KappModeratorModerator

10,327
2,243
Nov 17, 2011
VB = Vex* (Rb/(Ra+RB) -Rx/(Rx+Rc))

So by carefully chosing the Rs, almost any output voltage from 0 to Vex can be generated. A rather simple Choice is:
Ra = Rc
Rb = Mean(Rx)
with
Mean(Rx) = the mean value of the variable resistor = (Rxmax-Rxmin)/2
The output voltage results from the imbalance of the resistive dividers. So by more or less balancing/unbalancing the rresistor ratios you can set the voltage.

Harald

3. ### ykho21

3
0
Feb 4, 2012
Harald,

Thanks for your reply. RB=Rb? Today i just make an experiment to put in a single 1.5K variable resistor on this Rx. Since the change of resistance is high and affect the pressure reading (mV/V) output, I decided to put 1K resistor in series with 10 turn 100ohm variable resistor in Rx to make resistance change more precise. Means, Ra=1K, Rb=1K, Rc=1K and Rx=1K+100ohm 10 turn variable resistor. From this I can get the 1mV output. Is it alright to have a circuit built like this?

10,327
2,243
Nov 17, 2011
Yes,
that's o.k.

Harald

5. ### Resqueline

2,848
2
Jul 31, 2009
Here's a way to make an adjustment even more precise.
You change the values depending on the resistors you have access to and the adjustment range you want.

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6. ### ykho21

3
0
Feb 4, 2012
Hi,

Thanks for all for the comment and help. WIll try out both method to solve the problem.