Lab 3: Using A Multimeter

In this lab, we learned how to use a multimeter to test continuity, resistance and voltage.  The multimeter has many more functions but these are the functions we experimented with in the lab.


Continuity is tested by turning the multimeter switch to the icon that looks like a soundwave.  I used the probes to test continuity between paths on the circuit board I worked on in Lab 1.  The multimeter sends a small voltage through the probes and if the voltage comes through the circuit and back to the multimeter, the multimeter beeps and there is continuity.  The paths that were connected had continuity.


Next I tested the voltage of a 1.5V AA battery by adjusting the multimeter to 2V in the DC range.  The 1.5V battery read 1.449V which was only slightly less than the rating.


The 9V battery was then measured by the same process of connecting the probes of the multimeter to the positive and negative ends of the battery.  The 9V battery read 8.152V which was less than the 9V rating meaning it had been used a bit and lost some of it's charge since it was new.


It was also important to keep in mind that the multimeter has AC and DC modes when measuring voltage and you have to switch between the two when testing each one.  If not, your voltage reading will be 0.


We then tested the resistance of 5 resistors.  The value of the resistors was determined from the colored bands around the resistors.  The last color in the first 3 or 4 is a multiplier which tells you how many zeros to add.  The final color give you the tolerance of the component.  The 5 resistors I chose had a value of .68Kohms, 2.70Kohms, 470ohms, 100ohms, 1.00Kohms.  All the resistors had their resistance measured by the multimeter and touching the probes in any order on the ends of the resistor.  All five were very close to their rated resistance.


A potentiometer was tested next.  Potentiometers are resistors that can be adjusted.  I connected the multimeter across two adjacent pins and lowered the potentiometer as far as it would go and the reading was 0.8ohms.  Then I raised the potentiometer as far as I could and the multimeter read 9.76Kohms.  We were also able to tell if the potentiometer was linear by adjusting it to roughly half way and checking to see if the resistance was also roughly halfway between 0 and 10K.  The multimeter read 4.83Kohms which confirmed that the potentiometer was in fact linear.


The LDR (Light Dependent Resistor) was also tested.  By covering up the resistor, the resistance changes due to the change in light.  The max resistance I was able to achieve by covering the LDR was 0.515Mohms.


A similar procedure was followed when measuring a pressure dependent resistor.  After connecting to the multimeter, applying pressure to the resistor registered a change in the resistance.  The resting resistance without applying pressure was 350ohms.


The temperature dependent resistors were also tested in a similar fashion.  Once connected to the multimeter to measure resistance, I held the thermistor in my hand and noticed the increase in resistance.  My classmate also held the thermistor and since her hands were colder than mine, we were able to notice the difference in the two resistances based on the different temperature applied.

Lab 3 finished!