Science Buddies: "Ask an Expert"

Ok, so I am doing an experiment on building a model of an insulin pump (link:https://www.sciencebuddies.org/science- ... #procedure) and when I got to step 15 in the Testing the Artificial Pancreas section, the pump just continues running for me and doesn't stop by itself like its supposed to. I think this is because I didn't "normalize" the pump enough in step 11 in the same section. What does that step mean when it says to "normalize" the pump? Does it mean to leave the pump on with the conductivity sensor in the neutral solution until it shuts off by itself? I'm confused.

Hello khalidh223,

To “normalize” the pump, you should adjust the potentiometer in your circuit so that the pump stops when the conductivity sensor is in the neutral solution. When “normalized” the pump should start running when the conductivity sensor is placed in the acetic acid solution.

The circuit is designed to operate the pump when the conductivity sensor is in a fairly conductive solution (acetic acid). But the circuit requires an adjustment so that the pump does not operated in a less conductive solution (neutral solution).

I hope this helps. Please ask again if you have more questions.

A. Norman