Development and evaluation of a tutorial to improve students’ understanding of a lock-in amplifier

A lock-in amplifier is a versatile instrument frequently used in physics research. However, many students struggle with the basic operating principles of a lock-in amplifier which can lead to a variety of difficulties. To improve students’ understanding, we have been developing and evaluating a research-based tutorial which makes use of a computer simulation of a lock-in amplifier. The tutorial is based on a field-tested approach in which students realize their difficulties after predicting the outcome of simulated experiments involving a lock-in amplifier and check their predictions using the simulated lock-in amplifier. Then, the tutorial provides guidance and strives to help students develop a coherent understanding of the basics of a lock-in amplifier. The tutorial development involved interviews with physics faculty members and graduate students and iteration of many versions of the tutorial with professors and graduate students. The student difficulties with lock-in amplifiers and the development and evaluation of the research-based tutorial to help students develop a functional understanding of this device are discussed.

Figure 1

Example of a typical simulation question (left) and the associated “purpose” slide (right). For the simulation question, red bounding boxes indicate information that the student is expected to sketch or provide, consistent with the lock-in settings and/or output and green bounding boxes highlight settings that were changed from a prior simulation question.

Figure 2

Example of the explanations provided to students for each simulation (simulation 2 in this case). The “explanation” (left) features a conceptual description of the problem’s solution while the “mathematical explanation” (right) features the mathematics required to solve the problem.

Figure 3

An example of one of the tutorial questions which asks students to predict the input signal characteristics (left) and the answer to that question (right).

Figure 4

Examples of two types of hint commonly provided to scaffold student learning.