* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download OhmsLaw - OCExternal
Survey
Document related concepts
Galvanometer wikipedia , lookup
Valve RF amplifier wikipedia , lookup
Immunity-aware programming wikipedia , lookup
Power electronics wikipedia , lookup
Operational amplifier wikipedia , lookup
Opto-isolator wikipedia , lookup
Two-port network wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Surge protector wikipedia , lookup
Power MOSFET wikipedia , lookup
Electrical ballast wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Current source wikipedia , lookup
Rectiverter wikipedia , lookup
Transcript
Using LabPro for Ohm’s Law by Jim Sizemore Contents Introduction ..................................................................................................................................... 1 Objectives ....................................................................................................................................... 1 Equipment ....................................................................................................................................... 1 Ohm’s Law Measurement ............................................................................................................... 1 Making Current the x-axis ........................................................................................................ 2 Results ............................................................................................................................................. 4 Conclusion ...................................................................................................................................... 4 List of Figures ................................................................................................................................. 4 List of Links .................................................................................................................................... 5 Introduction Using the LabPro system (LabPro device and LoggerPro software) we will investigate Ohm’s law. The new information in this topic compared to the Vernier LabPro System Basic Setup and Operation and RC Time Constant and Energy Stored in Capacitor is making the xaxis another column besides time. We will also observe the same limitations in the current probe as observed in the RC Time Constant and Energy Stored in Capacitor experiment. Objectives Set up LabPro to measure current and voltage of characteristics of a resistor Making a column besides time the x-axis Observe linearity of voltage vs. current relationship thus establishing Ohm’s law Equipment LabPro system, LabPro voltage probe, LabPro current probe, electrical breadboard, electrical leads as required, resistors, electrical power supply, SPST switch, DMM. Ohm’s Law Measurement 1. Connect voltage and current probes to the LabPro (refer to Vernier LabPro System Basic Setup and Operation document for instructions how to plug in, turn on and calibrate LabPro system). 2. Use the DMM to measure actual values of resistors. 3. Construct an electrical circuit according to the schematic shown in Figure 1 as follows. LabPro’s current probe is rated at ±5 V, therefore, do not exceed 5 V on the power supply. LabPro’s voltage probe is rated for ±5 V and, therefore, is not a concern. A <5 V Variety of resistors V The voltmeter and ammeter are the probes connected to the LabPro system. Figure 1 – Schematic for discharging capacitor. 4. Set up Experiment > Data Collection at an appropriate value. I used 15 seconds, 250 samples per second as described in Vernier LabPro System Basic Setup and Operation. 5. Set power supply to ±5 V, start LabPro data collection and then turn power supply down to zero volts. Making Current the x-axis 6. Go to Graph Options dialog discussed in Vernier LabPro System Basic Setup and Operation. 7. Under x-axis select Current as shown in the next figure. Figure 2 – Select current as x-axis 8. Select range of data to fit curve to. 9. Navigate to Analyze > Curve Fit and obtain the following dialog box. Using LabPro for Ohm’s Law page 2 of 5 Figure 3 – Select proportional curve fitting. 10. Use the proportional curve fitting to obtain the following: Figure 4 – Ohm’s law curve fit for 100 resistor Using LabPro for Ohm’s Law page 3 of 5 11. Several resistors were measured and I won’t display pictures for all of them. However it is useful to reveal the problems with the current probe for at least one high resistance (low current) value. Shown next is the data for the 5600 resistor. At this point the data becomes quite unreliable. Apparently the current probe does well down to about 10mA, but lower than this can create problems. Figure 5 – Data for 5600 resistor Results Tabulated next are the results for resistance measurements. Nominal Resistance () 100 470 5600 8200 LabPro Measured value () 100.9 470.9 4474 5898 Due to the limitations of the current probe, the LabPro measurements at, I estimate, 1000 and higher resistances are unreliable. Conclusion This concludes the Ohm’s law experiment. It’s relatively simple, however has the added complication of setting the x-axis to something other than time. I also recommend, due to limitations of the current probe, to keep resistance values below 1000. As pointed out in the report on the RC time constant, it may be advisable to purchase a differential voltage probe and insert various shunt resistors to serve as a current probe. List of Figures Figure 1 – Schematic for discharging capacitor. ............................................................................ 2 Figure 2 – Select current as x-axis .................................................................................................. 2 Using LabPro for Ohm’s Law page 4 of 5 Figure 3 – Select proportional curve fitting. ................................................................................... 3 Figure 4 – Ohm’s law curve fit for 100 resistor .......................................................................... 3 Figure 5 – Data for 5600 resistor ................................................................................................. 4 List of Links 1. 2. 3. 4. 5. Vernier Web Site LabPro User’s Manual (large, 6.5 Mb file) LabPro Technical Manual (405 kb) Basic LabPro Setup and Operation RC Time Constant and Energy Stored in Capacitor Using LabPro for Ohm’s Law page 5 of 5