Day 1 - Review Exericse : Using a multimeter

The first experiment we did is to understand how to use a multimeter properly by examining

 different methods to use it

Resistance Test
1. Set up the multimeter to read resistance, which is located at the Ω symbol

2. The multimeter will show " L " when the probes are not touching anything

3. When we touched the two probes together, the multimeter will have a reading of 0.001Ω due to the internal resistance of the wire

4. We grabbed four different resistors and recorded the theoretical and measured values

Resistors Colors	Value from Colors(Ω)	Measured Value(Ω)
Red, Orange, Brown	230	218
Orange, Orange,Red	3300	3290
Orange,Orange,Brown	330	329
Red,Black,Red	2000	2010

Few Tips on measuring electrical componets

• Never measure resistance in a circuit when power is applied
• Discharge capacitors before measuring resistance

Voltage Test

1. To measure the voltage across an element, we need to set the multimeter to read direct current(DC) mode.
2. Touch the probes at the two ends of a 9v battery, we should get a reading that is close to 9V
Since the school are not able to provide new 9V batteries to every group; instead, we use 9V power supply to measure the voltage.

 3. Last, we tested the wall wart(adapter)plugs,
the value we get is 23.0V

Testing transformer-based adapter

when we measure a adapter that has labeled 18V, the value we get is 23V. The reason is that the adapter is really old one plus its an unregulated. That means, the voltage output is not constant.

When we use two clips to attach a 150 ohm resistor across the probes, the voltage reading did not change

Next, we set up the circuits as shown in the picture, with one 150 ohm resistor, 1 LED, and a power supply.

We measured the voltage at different places such as when we measure the voltage drop across the 150 ohm resistor, we got a value of 2.41V

When we measured the voltage drop across the LED  we got 2.13V

When we measured the voltage drop across the power supply, we got 4.54V

Out data makes sense if we added 2.41+2.13+4.54V  , we will get value close to 9.08V, which is the initial value of the voltage supply. Few reason that caused the inconsistency in values such as wired also dissipated some energy .

Current Test

We used the same set up as we used in the voltage testing experiment. This time, we were told to measure the current. To measure the current, we need to set the multimeter to A, which means ampere.  Then we need to break the circuit and insert the probes from the multimeter into series with the circuits to connect the circuit. If we do not measured in series, we might able to burn the fuses inside the multimeter.
The current value we measured is 15.9mA