Science Buddies: "Ask an Expert"

We are trying to perform an experiment from Science Buddies called "Measure your magnetism." It's at https://www.sciencebuddies.org/mentorin ... ?from=Home

We bought the supplies that were specified, except the Hall Effect cicruit that was specified wasn't available any more. So instead of a circuit that produces 5 mV/G we have one that only gives us 1.3 mV/G. However, we can set our voltmeter to measure a max of 2 volts dc instead of the 10 that the directions specify, so we think we should be ok.

We have gotten as far as observing the voltage with no magnet near the meter. It's low. But we can't get any reaction when we put any magnet near the meter.

We think that we must have connected something wrong, but how do we figure out what? Everything seems tight in the breadboard. Our voltage meter reads 8.63 volts when we directly measure our 9 volt battery. Can we measure voltage at other incremental places in this circuit to figure out what's wrong? Do you think we need MUCH stronger magnets?

thanks in advance for your help.

mary1234 wrote:We are trying to perform an experiment from Science Buddies called "Measure your magnetism." It's at https://www.sciencebuddies.org/mentorin ... ?from=Home

We bought the supplies that were specified, except the Hall Effect cicruit that was specified wasn't available any more. So instead of a circuit that produces 5 mV/G we have one that only gives us 1.3 mV/G. However, we can set our voltmeter to measure a max of 2 volts dc instead of the 10 that the directions specify, so we think we should be ok.

We have gotten as far as observing the voltage with no magnet near the meter. It's low. But we can't get any reaction when we put any magnet near the meter.

We think that we must have connected something wrong, but how do we figure out what? Everything seems tight in the breadboard. Our voltage meter reads 8.63 volts when we directly measure our 9 volt battery. Can we measure voltage at other incremental places in this circuit to figure out what's wrong? Do you think we need MUCH stronger magnets?

thanks in advance for your help.

Thanks for posting the link! That always helps.

You could check and see if your magnet will produce a measurable voltage change.

From the instructions-
"The sensitivity of the Hall sensor IC (A1321EUA) described in this experiment is 5 mV/G. Therefore, to calculate the magnetic field strength, B, in gauss, you can use this equation:
B = 1000 × (V0 − V1) / 5.

Your measurements, V0 and V1, are in volts. The factor of 1000 converts your measurement to millivolts, in which the Hall sensor is calibrated.
Use the equation to calculate the magnetic field strength for each magnet. (If you are using a different Hall sensor IC, substitute its sensitivity in the equation above.)"

So, you could use: B=1000x(V0-V1)/1.3
Or
(1.3*B)/(1000)= V0-v1.


I found one site that said a refridgerator magnet is 50 Gauss.

So, the change in voltage would be 0.065, which you may or may not see with your multimeter depending on how good it is and how much the measurement is fluctuating. You can look up the strengths of various types of magnets on the web, so I'd just check this calculation for your magnet and see if it is a number that you think you could measure.

Just to help other experts, what is "low" for voltage measured without the magnet at the Hall effect part.

Louise

Thanks. That is a help. We also discovered (with some help) that we had installed the Hall device backward. Now our big problem is the stability of our readings. There is a lot of fluctuation. But we're starting to at least have something.

mary1234 wrote:Thanks. That is a help. We also discovered (with some help) that we had installed the Hall device backward. Now our big problem is the stability of our readings. There is a lot of fluctuation. But we're starting to at least have something.

Cool! I hope it works out.

Louise