Lock-in amplifier laboratory

Lock-in amplifer instruction can be found on the website for Stanford Research Systems.

Basic Operation of SR830 Lockin amplifier

1. Read chapter 3 of the lockin manual

2. Folow the basic operation written in chapter 2.

3. After step 10 on page 2-4, answer why the values of x and y become noisy?

4. Now increase the frequency to 5 kHz. Now take down 10 different measurements of x. Find the average and standard deviations of your measurements. You should also take much finer measurements using Labview and a data acquisition board. Ask for a labview computer to be set up. You might also be able to take the time averaged value using one of our digital scopes.

5. Why the sync filter will improve your measurement?

6. Under what condition you should use this sync filter?

7. Now work on step 1 through 7 on pages 2-7 and 2-8. Use external function generator to explore the X, Y, R, and theta displays

8. Set the external function generator to exactly 1 kHz

9. After step 3, you can see that the X outpu is oscillating. What is the period of this oscillation?

10. At step 6, us the knob to adjust the internal refernce frequncy until there is no phase rotation. Finish step 7 to demonstrate that you can use external source as reference so the signal always has exactly the same frequncy as the reference.

11. Explore all steps in Chapter 2.

Measure the resistance of tungsten bulb at low bias

1. Use lock-in amplifier to measure the resistance of the tungsten bulb at current of 10 nA, 100 nA and 1 microAmp (AC current).

2. Use lock-in amplifier to measure the resistance of the tungsten bulb at the bias voltages up to 5 volts. You will need to devise your own circuit to perform this experiment.

Resistance of a copper wire

1. Take a copper wire with a length of 0.5, 1, and 2 m

2. Use 1 kohm resistor and measure the resistance of the copper wires

3. Determine the resistivity of copper

Measure the light intensity emitted by an LED

See the instruction given in a folder.