What Is a Source Measurement Unit or SMU? (2023)

Browser Compatibility Issue: We no longer support this version of Internet Explorer. For optimal site performance we recommend you update your browser to the latest version.Update Microsoft Internet Explorer



Provide us with your email address to get Analog Dialogue delivered directly to your inbox!

Follow Us

Join our Analog Devices Inc. community on Facebook to get exclusive content and much more!

What Is a Source Measurement Unit or SMU? (2) Follow Us

  • DEC 2017

    VOL 51


0 {{selected}}


{{#if PST}} {{/if}} {{#if PDP}} {{/if}} {{#if RESOURCES}} {{/if}}

myAnalog What Is a Source Measurement Unit or SMU? (3) What Is a Source Measurement Unit or SMU? (4)

  • myAnalog
  • {{#if projects}} {{#each projects}}
  • {{ title }}
  • {{/each}} {{/if}}

{{#if PST}}

(Video) How Does a Source Measure Unit (SMU) Work?

{{/if}} {{#if RESOURCES}}

{{/if}} {{#if PST}}

{{/if}} {{#if PDP}}

{{/if}} {{#if RESOURCES}}


(Video) What is a Source Measure Unit (SMU)?
{{savedTo}} What Is a Source Measurement Unit or SMU? (5)

{{#if PDP }}

{{productSavedTo}}{{resourceSavedTo}} ""

{{/if}} {{#if PST }}

{{tableSavedTo}} ""

{{/if}} {{#if RESOURCES }}

{{resourceSavedTo}} ""

{{/if}} {{#if PDP }}


{{#if PDP}} {{viewMySavedProducts}} {{viewMySavedResources}} {{/if}} {{#if PST}} {{viewMySavedProducts}} {{/if}} {{#if RESOURCES}} {{viewMySavedResources}} {{/if}}

byDoug Mercer Download PDF

A source measure unit (SMU) is an instrument that combines a sourcing function and a measurement function on the same pin or connector. It can source voltage or current and simultaneously measure voltage and/or current. It integrates the capabilities of a power supply or function generator, a digital multimeter (DMM) or oscilloscope, a current source, and an electronic load into a single, tightly synchronized instrument.

(Video) Understanding Source Measure Units
What Is a Source Measurement Unit or SMU? (6)

The ADALM1000 is a source measure unit at its heart, but it can also be viewed as a separate oscilloscope and function generator. However, because the output function (generator) and input function (oscilloscope) share a common pin when considered as separate, only one function can be used at a time.

Why Is It Important to Have a Programmable SourceMeasure Unit?

For some kinds of testing, it might not be important to have a programmable instrument. You may just want to read a value once or a small number of times. However, in many cases, it might be required to collect lots of data so that a plot or graph of the performance over time is generated. However, doing this manually is time-consuming and error-prone.

There are also lots of different experiments that require automated data collection to get faster or more accurate measurements or to take measurements over a long time-scale (months or even years). Here, you will certainly need a computer to collect the data and export it to a database for analysis.

Why Is It Important to Have Negative Voltages?

Not all experiments will need negative voltages and, in some cases, you can avoid this. However, many different types of devices work differently if a positive or a negative voltage is applied. To fully understand how such devices work, we need to be able to change the sign of the voltage applied. Each SMU channel in the ADALM1000 can only produce a voltage from 0 V to 5 V with respect to ground. Fixed 2.5 V and 5 V outputs that can both source and sink current are provided. The DUT could be connected between the 2.5 V output and the SMU output rather than to ground to sweep the voltage across the DUT from –2.5 V to +2.5 V. In addition, because the ADALM1000 has two SMUs, the DUT could be connected between the two SMU outputs. By sweeping one channel from 0 V to 5 V while sweeping the other from 5 V to 0 V, the voltage across the DUT goes from –5 V to +5 V.

As an example, consider a diode—a device that allows electricity to pass through it in only one direction. In order to evaluate if a diode is working, we need to see if it will pass current in both directions. We can do this in one of two ways. We can measure the diode in one direction, manually turn it around and measure it the other direction, and then combine the data sets together. However, we could just measure current flow when we apply both positive and negative voltages. In fact, this technique is so useful it is used to characterize many types of devices that have diode-like behavior—solar cells and light-emitting diodes are both good example cases. Figure 2 shows how to connect a diode to the ADALM1000 to sweep the voltage from –5 V to +5 V.

What Is a Source Measurement Unit or SMU? (7)

With Channel A programmed to sweep from 0 V to 5 V while Channel B is programmed to sweep from 5 V to 0 V, the difference between the channels appears across the resistor, which is used to limit the current and the diode. The time domain waveforms are shown in Figure 3. The green trace is Channel A voltage, the orange trace is Channel B voltage, and the yellow trace is Channel B current (the Channel A current is not shown, but would simply be the inverse of the Channel B current).

What Is a Source Measurement Unit or SMU? (8)

We can plot these measurements vs. each other and perform some simple math at the same time. What we want to plot is the current through the diode vs. the voltage across the diode. To calculate the voltage across the diode, we can subtract the voltage drop across the resistor (V = I × R) fromthe difference between the Channel A and Channel B voltages. The following Python equation (used in ALICE) does that:

What Is a Source Measurement Unit or SMU? (9)

Where the 100 is the value of the resistor. The plot of the diode current vs. that equation is shown in Figure 4.

What Is a Source Measurement Unit or SMU? (10)

What Are the Uses of a Source Measure Unit?

Many everyday objects will have been tested with an SMU as part of the factory test and quality control process. If you use LEDs to light your home or have solar panels on your roof, these will have been tested with an SMU as part of the manufacturing process.

The ADALM1000 is designed for use by engineering students who are studying the next generation of electronic devices. Understanding how a vast number of materials and devices conduct electricity, ranging from carbon nanotubes and quantum well heterostructures to biomembranes and biosensors, requires an SMU. In short, you can use the ADALM1000 to understand the electrical characteristics of any component at dc or low frequencies over a voltage range from –5 V to +5 V, measuring current from ±0.1 mA to 180 mA.

Can You Give Me a Specific Example of a Measurement That Needs a Source Measure Unit?

Take the example of a solar cell. In research labs, engineers are looking at ways to make more efficient, lower cost solar cells. In order to understand how well a solar cell is working, a small scale test device is produced—perhaps a few square mm to a few square cm in size—and then its performanceis characterized. These test cells are too small to generate any usable power beyond lighting, say, a single LED, but they are large enough to characterize the basic operating range and efficiency. This example lab uses the ADALM1000 to measure a small solar cell.

The key characteristic of a solar cell is how efficiently it converts sunlight energy into electrical power. This can be done by illuminating the test cell with a known intensity of light and measuring the electrical power produced per unit area. Since power is voltage multiplied by current, the starting point is to measure the terminal voltage (V) and current produced (I).

The voltage generated can be measured by connecting a voltmeter across the cell terminals while it is illuminated. Similarly, a current can be measured using an ammeter across the cell terminals. If we divide the measured current by the area of the solar cell, we get the current density.

However, there is a problem: if you multiply the voltage by the current (or current density), then this only tells us how much power (or power per unit area) we can generate if we had an ideal device. The reason is that a voltmeter has a nearly infinite internal resistance, and when we measure the voltage by itself, no current will be flowing. In this case, there is zero power being generated (measured voltage × zero current = zero). This measurement is called the open-circuit voltage. Similarly, when we place the ammeter across the terminals to measure the current, we are testing the cell when it has been short circuited, because an ammeter should have nearly zero internal resistance. In this case, there is current flowing but no applied voltage. Again, there is no power generated (measured current × zero voltage = zero). This measurement is called the short-circuit current.

For any practical (real) solar cell, the voltage that it outputs will depend upon how much current is being produced and this is why an SMU is used— so that the voltage can be varied while measuring the change in current.

The graph in Figure 5 shows a typical IV curve for a particular small solarcell (in this case, a 3 cm × 3 cm solar cell from a solar garden light). The current is negative because the current is going into (sunk by) the SMU channel. The current at 0 V is the short-circuit current and the voltage at 0 current is the open-circuit voltage.

What Is a Source Measurement Unit or SMU? (11)

The IV curve tells us how the voltage and current change and allows us to calculate the actual amount of power that a solar cell generates. Figure 6 plots the power in mW vs. the voltage across the cell. The power is simply V × I. The following Python equation calculates the power in mW:

What Is a Source Measurement Unit or SMU? (12)
(Video) Measurements with an SMU - Workbench Wednesdays
What Is a Source Measurement Unit or SMU? (13)

The peak of the graph is the point at which maximum power is generated (the so-called maximum power point). The power is negative because the SMU is absorbing the power produced by the cell.

If we used the technique from Figure 2, we could also measure the solar cell when a negative voltage is applied (reverse bias). This gives us some useful information. Firstly, it tells us that the device doesn’t break down under reverse bias. This is a sign that the device is of good quality. Secondly, it tells us whether there is any extra current available. By applyinga negative voltage, we can effectively suck charges out of the device thatwouldn’t otherwise be extracted. While these sucked charges can’t be used to generate power (we’re actually putting power into the device at this point, rather than extracting it), it allows us to understand some of the photo current loss mechanisms. Thus, measuring IV curves is one of the most important tools used in solar cell development and optimization. Similarly, taking IV curves is extremely important to understanding a wide range of other device types, including LEDs and OLEDs, transistors, sensors, and many more other devices.

What Is a Source Measurement Unit or SMU? (14)

Starting with this article, we will begin a monthly series around the SMU ADLAM100 and show some interesting experiments with it. In case you want to follow the experiments and are interested in the ADALM1000, you could get them from our distributors: Digi-Key and Mouser.


Question 1:

In Figure 5, the maximum power of a solar cell is given. Which physical
size has an influence?

Question 2:

What is the maximum power you could get out of the solar cell?

Question 3:

How is the function called to keep the output power at the maximum level?
(Tip: see ADP5091)

You can find the answers at the StudentZone blog.


What Is a Source Measurement Unit or SMU? (15)

Doug Mercer

Doug Mercer received his B.S.E.E. degree from Rensselaer Polytechnic Institute (RPI) in 1977. Since joining Analog Devices in 1977, he has contributed directly or indirectly to more than 30 data converter products and holds 13 patents. He was appointed to the position of ADI Fellow in 1995. In 2009, he transitioned from full-time work and has continued consulting at ADI as a fellow emeritus contributing to the Active Learning Program. In 2016, he was named engineer in residence within the ECSE department at RPI.

    • Region
    • Korea
    • India
    • Taiwan
    • Singapore
    • Languages
    • English
    • 简体中文
    • 日本語
  • Modal title

    (Video) Using a PXI Source Measure Unit (SMU)


    What is a source measurement unit SMU? ›

    A source measure unit (SMU) is an instrument that combines a sourcing function and a measurement function on the same pin or connector. It can source voltage or current and simultaneously measure voltage and/or current.

    How does SMU measure current? ›

    Operation. A SMU integrates a highly stable DC power source, as a constant current source or as a constant voltage source, and a high precision multimeter. It typically has four terminals, two for source and measurement and two more for kelvin, or remote sense, connection.

    What is SMU vs PPMU? ›

    Furthermore, SMUs can limit voltage and current completely programmatically while PPMUs have the ability to limit voltage but only regulate current based on selected ranges. Applications with sensitive DUTs that need to be closely monitored should consider using SMUs as they provide full limiting capabilities.

    What is a sourcemeter used for? ›

    A sourcemeter is an electronic instrument capable of generating currents and voltages and simultaneously measuring them with high accuracy. A sourcemeter is also called a Source Measure Unit or SMU.

    What does SMU mean production? ›

    Special make-up is when a Brand (i.e. supplier) manufactures an item that is special for a retailer. SMU orders typically have Minimum Order Quantity (MOQ) restrictions associated with them.

    Where is SMU from? ›

    A nationally ranked private university located near the heart of Dallas, SMU is a distinguished center for global research and teaching.

    What is SMU specification? ›

    An SMU is, in-fact, a precision “source” and a precision “measure” in one “unit” or chassis; the “source” can be set up as either a voltage source, or a current source, and the “measure” can be a measurement of voltage, current, or resistance.

    What is SMU IV measurement? ›

    What is a Source Measure Unit (SMU)? An SMU combines the capabilities of a current source, voltage source, current meter and voltage meter into a single unit. This gives it the ability to evaluate the IV characteristics of devices across all four measurement quadrants without the need for any additional equipment.

    What is the full form of SMU? ›

    Definition:Sikkim Manipal University
    Category:Academic & Science » Universities & Institutions
    Country/ Region:India

    What is SMU proud of? ›

    The mission of SMU Pride is to connect SMU LGBTQ+ alumni to one another, our allies and the University through meaningful events and volunteer and giving opportunities. We work to elevate the profile of LGBTQ+ alumni so the community can be aware of our existence and contributions.

    Is SMU good for international students? ›

    SMU graduates are highly sought after by top employers locally and internationally. Our graduates consistently rank top in Singapore in terms of higher starting salaries and strongest employment rates amongst all Singapore government-funded universities.

    Who broke the SMU scandal? ›

    David Stanley. In June 1986, John Sparks, a producer at Dallas–Fort Worth ABC affiliate WFAA-TV, received a tip from a former athletic department employee named Teresa Hawthorne about further wrongdoing at SMU. Sparks' investigation eventually led him to David Stanley, a former Mustangs linebacker from Angleton, Texas.

    What multimeter can measure? ›

    Digital multimeters are measuring instruments that can measure quantities such as voltage, current, and resistance. Measured values are shown on a digital display, allowing them to be read easily and directly, even by first-time users.

    What is source current meter? ›

    Source Meters

    We have established that a Source Meter Unit (SMU) is a tool that can measure and source voltage or current. A source meter has all the features you will find with a (DMM) Digital Multimeter all in one inclusive and compact including power supply, current source, electronic load and pulse generator.

    What is SMU in VLSI? ›

    Abstract: An implementation of the Viterbi algorithm (VA) can be divided into three basic units, the transition metric unit, the added-compare-select unit, and the survivor memory unit (SMU).

    What is SMU grading scale? ›

    Grading Policy:
    1 more row

    What does SMU stand for in text? ›

    Start Me Up. SMU. Shut Me Up (music single) SMU.

    What does SMU mean in maintenance? ›

    The Software Maintenance Upgrade (SMU) is a package that can be installed on a system to provide a fix or a security resolution to a released image.

    Why is it called SMU? ›

    SMU was founded on April 17, 1911, by the Methodist Episcopal Church, South—now part of the United Methodist Church—in partnership with Dallas civic leaders. However, it is nonsectarian in its teaching and enrolls students of all religious affiliations.
    Southern Methodist University.
    MottoLatin: Veritas liberabit vos
    23 more rows

    What does SMU hours stand for? ›

    'SMU Hours' means the engine hours based on the Service Meter Unit for each piece of Equipment.

    What does SMU offer? ›

    SMU offers 109 bachelor's degrees, 112 master's degrees, 27 doctoral-research degrees, one doctoral-professional degree and one specialist degree, through seven schools: Dedman College of Humanities and Sciences. Meadows School of the Arts. Cox School of Business.

    What should a personal statement include SMU? ›

    While writing your personal statement, admission officers look for the following:
    1. An insight into your background and how it has shaped your personality.
    2. Your formative experiences.
    3. Important events/ significant achievements that have led to changes in your life.
    4. Your interest in your course choice.
    Jun 14, 2020

    What are the minimum requirements at SMU? ›

    Include the following documents: cer fied copies of your ID/passport; Grade 11/12 results; academic 2022/23 Page 8 · Official academic record(s) from previous university (ies) a ended, including SMU (if applicable). Proof of applica on fee payment (copy of deposit slip). Or email to: apply@smu.ac.za.

    What is SMU speech code? ›

    Southern Methodist University has been given the speech code rating Yellow. Yellow light colleges and universities are those institutions with at least one ambiguous policy that too easily encourages administrative abuse and arbitrary application.

    What are the sources of measurement? ›

    Measurement errors are commonly ascribed to four sources: the respondent, the interviewer, the instrument (i.e., the survey questionnaire), and the mode of data collection.

    What are the 3 units of measurement system? ›

    The three standard systems of measurements are the International System of Units (SI) units, the British Imperial System, and the US Customary System. Of these, the International System of Units(SI) units are prominently used.

    What are the 3 different types of units of measure? ›

    Systems of measurement in modern use include the metric system, the imperial system, and United States customary units.

    What are the four 4 types of measurement data? ›

    Psychologist Stanley Stevens developed the four common scales of measurement: nominal, ordinal, interval and ratio. Each scale of measurement has properties that determine how to properly analyse the data. The properties evaluated are identity, magnitude, equal intervals and a minimum value of zero.

    What are the four types of unit of measurement? ›

    The four basic units of measurement of length are:
    • Millimetre: One millimetre is equal to micrometres or nanometres.
    • Centimetre: A centimeter is a metric unit used to measure length. One centimeter is equal to ten millimeters or. ...
    • Inch: One inch is equal to. millimeters or. ...
    • Foot: One foot is equal to inches or. centimetres.

    What are the 5 types of measurements? ›

    types of measurements are:
    • Indirect method of measurement.
    • Direct method of measurement.
    • Fundamental method of measurement.
    • Substitution method of measurement.
    • Comparison method of measurement.


    1. Current-voltage (IV) measurement fundamentals by using SMU (Source/Measure Unit) [SMU PACT#36]
    (Keysight Technologies, Inc.)
    2. Was ist eine Source Measure Unit (What is a Source Measure Unit, SMU)?
    3. Rohde & Schwarz NGU source measure units (SMU) - Introduction
    4. B2900B/BL: SMU Capable of Measuring Very Low Signals (Part 1 of 3)
    (Keysight Hands-On)
    5. DIY Source-Measure Unit SMU Chapter 1
    (Erickson Engineering)
    6. EEVblog #607 - Agilent B2912A Source Measure Unit SMU Teardown
    Top Articles
    Latest Posts
    Article information

    Author: Lakeisha Bayer VM

    Last Updated: 11/07/2022

    Views: 6647

    Rating: 4.9 / 5 (49 voted)

    Reviews: 80% of readers found this page helpful

    Author information

    Name: Lakeisha Bayer VM

    Birthday: 1997-10-17

    Address: Suite 835 34136 Adrian Mountains, Floydton, UT 81036

    Phone: +3571527672278

    Job: Manufacturing Agent

    Hobby: Skimboarding, Photography, Roller skating, Knife making, Paintball, Embroidery, Gunsmithing

    Introduction: My name is Lakeisha Bayer VM, I am a brainy, kind, enchanting, healthy, lovely, clean, witty person who loves writing and wants to share my knowledge and understanding with you.