In order to begin testing a fuel cells and other alternative energy devices, it’s important to understand both what you’ll be testing and what equipment you’ll use

The first term to know is current. Electric current is the rate at which electrically charged particles flow through a material. An electric circuit is the conducting path for this flow of charged particles, or current, and current is measured in Coulombs per second, also known as amperes, or amps. An amp is 1 coulomb of charge passing a point in an electric circuit in one second.

Another term to know is resistance. Whenever an electric current is established in an electric circuit, it experiences what is known as resistance, or the opposition to the flow of electric current. Resistance is the property that impedes the flow of current in a material, and it is measured in ohms. The greater the resistance, the smaller the current.

Voltage is a way of using numbers to describe an electric field, known as an electromotive force, or EMF. EMFs are measured in volts over a distance, such as volts per centimeter. A stronger EMF has more volts per centimeter than a weaker one. To understand how voltage works, think about the flow of current as water flowing through a faucet. Voltage causes the electrical current to flow through a circuit in the same way that water pressure causes water to flow through the faucet. If the water pressure increases, more water flows through a faucet; in the same way, if the electrical pressure, or voltage, increases, more current flows through the circuit. If the water is turned off, no water flows through the faucet, and if the voltage source, or EMF, is removed, no current will flow through the circuit.

One device that measures current, resistance, and voltage, or amps, ohms, and volts, is the multimeter, or multipurpose meter. A multimeter is used to make various electrical measurements, such as AC and DC voltage, AC and DC current, and resistance. It is called a multimeter because it combines the functions of a voltmeter, ammeter, and ohmmeter. Multimeters may also have other functions, such as diode and continuity tests.

In general, to use a multimeter, first turn the meter on and insert the probes into the correct connections. One of the most common mistakes made in using this device is not inserting the test leads in the proper jacks for the type of test you’re doing. Depending on what you’re testing for, set the switch to the correct measurement type and range, being sure to set the maximum range higher than the anticipated range. Selecting a higher range will keep the meter from being overloaded.