Introduction
A number of equipments are used in carrying out experimental activities in the laboratory. Knowledge of the use of these equipments is very critical to the success of experimental activities in the lab as well as ensuring the safety of the components as well as the person carrying out the experiments.
2. Purpose
The purpose of this experiment on equipment usage and measurement is to be familiar with the way to properly handle and use laboratory equipment and based on the knowledge of the equipment learnt know how to set up experiments using these equipment.
3. Equipment
The equipment used in this particular laboratory setup include the following
Function generator
Oscilloscope
Digital Multi-meter
Triple output power supply
The triple output voltage power supply is the source of DC power as used in the laboratory. As the name implies, this DC voltage power source has three voltage outputs which are +6V, +20V and -20V. The +6V voltage source has a supply range between 0V to +6V DC, the +20V has a range between 0V to +20V while the third voltage source of -20V has a constant ratio with the +20V DC source.
For this lab experiment, these voltage sources of +6V, +20V and -20V DC are labeled as V6, V+ and V- respectively.
4. Procedure
A: DC Voltage Measurements
In order to take the DC voltage measurements, the V+ DC source of the power supply was set to +12V while the V- DC source of the power supply was set to -6V using the track knob. The ratio of 2:1 between the V+ source and the V- source is maintained as verified by observing the change in the value of V- after changing the value of V+ to +18V. The value of V6 was set to +6V, V+ was set to +18V and V- was set to -18V as reference values for the DC voltages. The various values of the output voltages for different connection configurations were measured using the terminals of the multi meter and the values recorded as presented in table 1.
B: DC Voltage Measurement using the Oscilloscope
Figure 1: Circuit connection for voltage measurement using the oscilloscope
Another probe was connected to channel 2 of the oscilloscope and the +6V supply of the triple voltage DC power supply and the voltage supply of the +6V supply was adjusted to 5V. Observing the output trace on the oscilloscope, two straight lines representing the two input voltages connected through channel 1 and channel 2 of the oscilloscope were observed on the screen. The value of the output voltage Vout was then measured from the oscilloscope reading and also using the digital multi meter. The result of the output voltage reading is as presented in table 2.
C: Math Function
In order to learn to use the math function of the oscilloscope, the channel 1 of the oscilloscope was connected to the 5V of the DC power supply and the channel 2 connected to the 12V of the DC power supply. The coupling of the two channels on the oscilloscope was then set to DC and the following operations were performed on the oscilloscope using the MATH function and the corresponding results displayed as obtained.
CH1 + CH2
CH1 - CH2
CH1 x CH2
5. Calculations
Percentage error
The percentage error between the estimated values (oscilloscope readings) and the actual readings (theoretical readings) were calculated using the formula
Percentage error= estimate-actual valueactual vaue X 100
where, estimate is the oscilloscope readings and actual value is the theoretical reading
For estimate = 10.20V and actual = 10.10V
%error= 10.20-10.1010.10 X 100
= 99.0%
For estimate = 4.80V and actual = 5.04V
%error= 4.80-5.045.04 X 100
= 4.76%
6. Discussion
The experimental activities carried out in this lab were divided mainly into two sections. In the first part, the use of two major equipments was learnt. These equipment were the triple output DC power supply and the digital multi meter. The use of the DC power supply module to supply varying amounts of voltage irrespective of the combinations used for the connection was learned. It was learnt that any of the voltage source could be used as reference (low end) while still obtaining the desired voltage value by connecting to the appropriate high end. The use of the digital multi meter to measure output voltage from the DC power supply module was also learned in this first part of the exercise. This knowledge was useful in carrying out the second section of the experiment.
In the second part of the experiment, the use of the oscilloscope for voltage reading was learned. The oscilloscope was used to simultaneously read voltage from two channels. It was further learnt how to use the oscilloscope MATH function to monitor the summation of difference of input into the two channels of the oscilloscope.
Using the values of the estimate which is the reading obtained from the oscilloscope and the actual value which is the theoretical value of the measured voltage obtained from the multi meter, a percentage error of the readings was calculated. This difference in the readings of the voltage from the same output could be attributed to the difference in the internal construction of the multi meter and the oscilloscope. The internal resistance of the equipment and the voltage drop across the connecting wires are accountable for the difference in measured voltage values.
7. Conclusion
The purpose of this lab experiment to understand the use of DC voltage supply, digital multi meter and oscilloscope has been met. The DC voltage supply can be adjusted to supply different voltage values. The digital multi meter as well as the oscilloscope can be used to measure voltage values. Voltage from two sources can be monitored simultaneously on the oscilloscope. The knowledge of the use of these equipments is very important to successful laboratory activities in the study of electronic circuits.
Note
Kuphaldt, Tony R. Lessons In Electric Circuits, Volume I - DC . Open Book Project, 2005.
