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What is a Source Measure Unit?

Ossila Source Measure Unit in combination with our IV software to measure I-V sweeps
The Ossila Source Measure Unit

A source measure unit (also known as a source meter or SMU) is a tool that can power your electronics and measure their performance at the same time. Like a Swiss Army Knife, it combines the capabilities of several instruments into one compact package, saving bench space, time, and programming issues. But what exactly does it do?

Each SMU channel can:

  • Source. Precisely generate and control either voltage or current.
  • Measure. Measure voltage and current at the same time.

SMUs can perform the role of multiple components in one synchronized unit. They can act as an ammeter, a voltmeter, and a power source. For example, the Ossila Source Measure Unit can source voltage, while simultaneously measuring current and voltage.

The Ossila Source Measure Unit can supply current and display live voltage and current through one channel
Our SMU supplying voltage while measuring current and voltage across a resistor.

Applications of a Source Measure Unit

Source measure units can measure and characterize many electronic devices and material properties. Some applications include:

  • LED and OLED characterization
  • Solar cell I-V curves and stability measurements
  • Measuring transistor properties, such as current gain
  • Measuring battery discharge rates (V Sense channels only)
  • Testing electronics components
  • Testing materials by measuring conductivity, leakage currents, and other properties

Why Use A Source Measure Unit?

Easy To Control

SMUs are easily programmable and user-friendly. This streamlines the measurement process, compared to managing separate inputs and outputs.

Fast Measurement Speed and Increased Accuracy

Multiple channels on a source measure unit
Our SMU has multiple channels for complex measurements

Integrating multiple functions into one system reduces measurement time. Combined with minimal signal loss and measurement errors, this leads to more accurate measurements.

Compact and Budget-Friendly

With fewer systems involved, choosing an SMU saves money and lab space.

Handling Negative Voltages

Some electronic devices need to be tested under both positive and negative voltages. Source measure units can do this easily, without resetting the system or rearranging the setup.

Multiple Channels

The multiple channels in an SMU allow complex measurements to be taken.

Multiple Measurements

SMUs can take multiple measurements in rapid succession. This is great for obtaining quick snapshots of devices (e.g. I-V curves) or for measuring dynamic behaviour.

Can You Use Individual Components Instead?

You could potentially build a system that can do what a source measure unit can do, with moderate accuracy, using individual components. To do this, you would need to combine several individual components:

  1. A benchtop power supply to output voltage
  2. Several good quality multimeters
    • One to measure voltage
    • One to measure the current
  3. An external data control center, such as a computer, to coordinate measurement
Multimeters, power supplies, connector boards and control devices require individual connection to take current voltage measurement
You can combine individual components together to take I-V curve measurements, but this required significant configuration and set up time.

However, if you are combining equipment in this way, there are significant drawbacks to consider:

  • It is difficult to programme
  • The cost of individual components can add up quickly
  • You must rearrange the system to measure both positive and negative voltages
  • Human error can be a big issue
  • Combining multiple components introduces a delay

Source Measure Unitscombine these components into one convenient unit. This allows you to conduct different measurements for different samples using only one piece of equipment

Source measure units can conduct many types of measurements iwthout the need for individual components.
Source measure units combine the function of individual components into one unit.

So, What is a Source Measure Unit?

Overall, a source measure unit is a multi-talented tool for electronics, combining a power source and measurement functions in one. An SMU is a useful addition to any electrical characterization lab.

Source Measure Unit

Source Measure Unit

Contributing Authors

Written by

Dr. Mary O'Kane

Application Scientist

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