Using a Multimeter

Purpose
      The purpose of this lab is to review on how to correctly use the multimeter to measure current, voltage and resistance in a circuit.

Resistance Test
When the multimeter probe doesn't touch anything, the multimeter reads overload in the multimeter. When the probes is touching each other, it reads 0Ω. After this test is conducted, 4 different resistors are measured its resistance and the result is compiled to this table:

Resistor Colors	Value from Colors	Measured Value	%error
Brown black brown	100Ω	97 ± 0.05 Ω	3.0%
Brown red orange	12000Ω	11.5 ± 0.05 kΩ	4.2%
Orange white yellow	390000Ω	392 ± 0.5 kΩ	0.51%
Red black red	2000Ω	2.02 ± 0.005 kΩ	1.0%

According to the result from the measured value, it actually make sense since the percent error is under five percent which is the tolerance for resistors that have a gold band.

Voltage Test

In this part, a voltage with rating of 12VDC was measured. Since its an unregulated voltage source, a reading of 17.34 V makes sense since it guarantees voltage of 12 V.

Circuit

A circuit consist of a power source, 150 Ω resistor and LED was constructed as follow

The setup of the circuit where the power source positive terminal is connected to the resistor and the negative terminal to the negative side of the diode.

Once the circuit is built, the voltage across the LED and the resistor was measured as shown on the picture below

Probes are set up so it is parallel to the circuit and each elements' voltage drops are measured

The result of the voltage drop is as follow:

    Voltage across resistor = 2.50V

    Voltage across diode = 2.24V

After the voltage was measured, the current was then measured as well. The setup is shown below:

multimeter was set up to measure the current by attaching it in series to the circuit

As seen in the picture, the current is measured to be 26.3 mA.

There is some discrepancy in the value of measured current and the ideal current calculated using Ohm's Law which is the I = V/R. The calculated I appears to be 0.033 A which has 20% error. This error is created because the LED have some resistance that contributes to the error.