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PHYS 351 · Advanced Instrumentation

Lab 2 · Voltage mixing & squaring

SlidesLecture notesLab 1Lab 2
PHYS 351 LAB 2
Voltage Mixing and Squaring
© Ran Yang, Ph.D.
SUBMISSION   Submit the completed lab report as a PDF on Gradescope.

Due: 2:00 p.m. next Monday.

Policies and Instructions
  1. Report Format: Submit a formal, typed lab report in PDF format. Handwritten lab reports will not be accepted. Hand-drawn circuit schematics are allowed only when explicitly permitted in the task instructions. Include screenshots, code, and simulation or measurement results where specified.
  2. AI Policy: The use of any AI tool, including a large language model (LLM), to write, generate, debug, or modify code or any portion of the lab report is prohibited unless the course instructor grants explicit permission in advance. A teaching assistant (TA) cannot grant permission to use AI tools.

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Introduction

This lab explores the use of an AD633 analog multiplier to generate the product of two input voltages. You will implement a voltage-squaring function, measure its accuracy, and investigate methods for minimizing offset errors based on the datasheet recommendations.

Equipment and Components

Available equipment includes resistors, potentiometers, two fixed ±15 V power supplies, and connecting wires.

Tasks

  1. Voltage Product Generation:
    1. Use an AD633 mixer to generate the product of two input voltages.
    2. Use an approximately 0.1 µF capacitor to decouple each supply rail.
    3. Connect the two inputs to create a voltage squaring function.
    4. Measure the output voltage over a sufficient number of input-voltage values to evaluate the device’s accuracy. Obtain approval from the course instructor or a TA.
    5. Perform a quadratic curve fit in your lab report, including the Python fitting code and resulting plot.
TASK APPROVAL Task 1 (Voltage Product Generation)

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  1. Error Sources:
    1. Consider the following sources of error in the device:
      • Offset errors on the inputs and outputs
      • Scale-factor error
      • Nonlinearity
    2. Consult the datasheet to identify methods for minimizing offset errors.
    3. Design and build an offset adjustment circuit to correct the errors.
    4. Include detailed circuit diagrams in your report.
TASK APPROVAL Task 2 (Error Sources and Offset Adjustment)

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  1. Inverse Function:
    1. Ensure that the offset voltages are less than ±50 mV.
    2. Incorporate the squaring circuit into a feedback loop to generate its inverse function, the square root.
    3. Measure the output voltage over a sufficient number of input-voltage values to evaluate the circuit’s accuracy. Obtain approval from the course instructor or a TA.
    4. Perform a square-root curve fit in your lab report, including the Python fitting code and resulting plot.
TASK APPROVAL Task 3 (Inverse Function)

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Submission Reminder

  • Circuit diagrams for the multiplier/squaring circuit and the offset-adjustment circuit.
  • Your Python fitting code and plots for both the quadratic (squaring) and square-root curve fits.
  • A discussion of the error sources (offset, scale-factor, nonlinearity) and how you minimized them.
  • Your measured offset voltages confirming they were within ±50 mV before the inverse-function task.
  • A discussion of any challenges encountered and how you overcame them.

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