Help with a little project I'm trying to do:

[Specimen]

Hello All,

I'm planning to do a relatively simple project.

What it consists of is a wheatstone bridge. I'm making a wheatstone bridge connection with 3 resistors and one unknwown resistor which is a pressure sensor. I know that the sensor changes from say 5,000 ohms (originally) to a maximum of 22,000 ohms.

Now, I am trying to find 3 ideal resistor combinations of the remaining in the wheatstone bridge which would give me MAXIMUM voltage variation with just a little amount of pressure on the sensor.

I'm trying to play around with different resistor value combinations going high/ low etc ... but when will I know when I have hit the ideal combination? Would appreciate any help for the same ...

Thanks!

 

[ranger]

When you design a wheatstone bridge with the intent of interfacing with a sensor whose resistance changes wrt some physical phenomena; you start from a null condition or from a balanced condition. This is when the bridge is balanced or the voltage out is zero. It just makes it easier to measure changes in resistance of the sensor.

For this you will need four known resistances. The extra fourth one will be used to balance the bridge. Now from this null position, any changes in resistance from your pressure sensor will cause the bridge to come out of balance.

If you want maximum voltage variation, why not amplify the output of the bridge with a differential amplifier? Also note that you won't want a too great of a change in your sensor's resistance as this will cause nonlinearity and isn't good if you plan on making some sort of calibration curve.

 

[sir-pinski]

Hi there,

It sounds like you're working on an interesting project! Finding the ideal resistor combination for your wheatstone bridge can be a bit tricky, but here are a few tips that might help:

1. Start by calculating the total resistance of your wheatstone bridge. This can be done by adding the known resistors in parallel and then adding them in series with the unknown resistor. This will give you the total resistance of the bridge.

2. Next, you can use Ohm's Law (V=IR) to calculate the voltage across each resistor in the bridge. Keep in mind that the voltage across the unknown resistor will vary with pressure, so you'll need to use different values for R in this calculation.

3. As you mentioned, you can play around with different resistor values to see which combination gives you the maximum voltage variation. One approach could be to start with a relatively low value for the unknown resistor and gradually increase it until you see a significant change in voltage. This will give you a starting point to work with.

4. You can also use a multimeter to measure the voltage across the unknown resistor at different points of pressure. This will give you a better idea of how the voltage varies and can help you determine the ideal combination.

I hope this helps! Good luck with your project.