There are some basic things you need to realize.

• You all make measurements.  You measure things like temperature, pressure, pH, rotational velocity and many other physical quantities.
• When you make a measurement you use a sensor.
• In-class, we will look at a thermocouple, which is a temperature sensor.
• Many sensors (but not all) will produce an electrical signal - usually a voltage.
• Because sensors produce a voltage, you need to understand what voltage is.
• Because sensors produce a voltage, you need to learn how to measure voltage.
• Voltage is measured with various kinds of voltmeters.
• In class, we will look at a voltmeter.
• You will notice the voltmeter has two leads.
• Turn to your partner and try - between the two or three of you - to come up with an answer to the question "Why does the voltmeter have exactly two leads?"
• In class we will work on the question of why one lead is black and one is red and what that means.
• Next, we will measure a few voltages.
• We will measure the voltage of a battery.
• We will measure the voltage of a thermocouple.
• Finally, we will discuss what all of this means.
• One thing we glossed over is the idea that some voltmeters have one lead (usually the black lead) connected permanently to ground.  (That often happens in oscilloscopes which are a truly special kind of voltmeter,)