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Why You Want an ORP Sensor

Graph of redox titration with Go Direct ORP Sensor

An Oxidation Reduction Potential (ORP) Sensor measures the activity of oxidizers and reducers in an aqueous solution. It is a potentiometric measurement from a two-electrode system similar to a pH sensor. Sometimes it is also referred to as a redox measurement. Unlike a pH sensor, an ORP sensor measures the ratio of oxidized to reduced forms of all chemical species in solution.

The ORP sensor is made up of two electrochemical half cells where the reference electrode is generally Ag/AgCl and the measurement electrode is commonly Pt. The potential difference between the two electrodes represents the redox potential of the solution being measured and can be described by the Nernst equation.

E = Eo – 2.3 (RT/nF) x (log [Ox] / [Red])

Where:

  • E = total potential developed between the measurement and reference electrodes
  • Eo = a voltage specific to the system
  • R = gas constant
  • T = temperature in K
  • n = the number of electrons involved in the equilibrium between the oxidized and reduced species
  • F = Faraday constant
  • [Ox] = concentration of the oxidized species
  • [Red] = concentration of the reduced form of that species

The output of the ORP sensor is relative to the reference electrode. For example, a reading of +100 mV indicates the potential is 100 mV higher than the potential of the reference half cell and suggests an oxidizing environment. Likewise, a –100 mV reading indicates a potential 100 mV lower than the reference half cell and is a reducing environment. In some applications, redox potential may be reported as Eh which is the voltage reading with respect to the Standard Hydrogen Electrode (SHE). By taking into account the offset of the reference electrode used in the ORP sensor, the potential can be converted into Eh readings. Vernier ORP sensors use a Ag/AgCl saturated KCl reference electrode.

In education, a common application for an ORP sensor is a potentiometric titration. Similar to an acid-base titration, a titrant is added to a sample incrementally until all the sample has reacted and the end-point is reached. One example where students can apply their understanding of redox is by using a Vernier Go Direct ORP Sensor to determine the concentration of H2O2 by titrating the solution with KMnO4. To correctly calculate the concentration, students must understand the balanced redox reaction between KMnO4 and H2O2.

Vernier Tip: Check out two additional experiments from Vernier using an ORP Sensor.

Graphical Analysis 4.4 Update for Computers, Chromebooks, and Android

Version 4.4 of Graphical Analysis for ChromeOS, macOS, Windows®, and Android is now available. The Chrome version is in the Chrome Web Store, the computer versions are available on the Vernier Graphical Analysis web page, and the Android version is available in the Google Play Store.

We’re very excited about this release as it includes support for photogates in the most common modes of motion, gate, and pulse timing. It is also the first release of the Android version, which adds support for Go Direct® sensors!

New Features

  • Tangent line analysis feature
  • Support for Photogate when used with LabQuest interfaces (not yet available on Android)
  • Lithuanian language support
  • Android platform now has the same user interface as macOS, Windows, and ChromeOS
  • Interface can be scaled for larger font size and thicker graph traces

Download the update for Graphical Analysis 4 »

NSTA Blog Reviews Go Direct® Motion Detector

Go Direct Motion Detector

NSTA Recommends recently featured the Go Direct® Motion Detector in the article, “The Vernier Go Direct Motion Detector: A Modern Twist on a Timeless Design,” Reviewer Martin Horejsi provides interesting background and history on ultrasonic motion detectors before highlighting the “mid-21st century finesse and rigor,” features, and overall functionality of the Go Direct® Motion Detector.

In the review, Martin says:

“The mobility of the Vernier Go Direct® Motion Detector opens up new channels of scientific inspection. Of course there is the highly accurate and fast motion detection, but there is also the ability to easily navigate materials and angles, and interference, and most anything else one can think of at the intersection of the Vernier Go Direct® Motion Detector and sound material science (pun intended).”

And, he concludes by saying:

“The word echo, by the way, stems from the story in Greek mythology about a cursed nymph who was doomed to only repeat the last words anyone spoke to her. My guess is today’s students will echo each other when using the Vernier Go Direct® Motion Detector by repeating single words over and over like, “Cool” and “Wow!””

The complete Go Direct family of sensors offers teachers and students maximum versatility to collect scientific data either wirelessly or via a USB connection. These low-cost sensors can be used in more than 300 teacher-tested experiments developed by Vernier and are supported by free graphing and analysis software, the Graphical Analysis™ 4 app.

Read more about the Go Direct Motion Detector on NSTA Recommends»

Vernier Sponsors the 2018 KidWind Challenge

To inspire students to learn about renewable energy and hone their engineering skills, Vernier supported the 2018 KidWind Challenge, hosted by KidWind. The challenge consists of dozens of local and regional competitions across the country, called KidWind Challenges, during which teams of students test the energy output of wind turbines they designed and built. Students also present their design processes to a panel of judges and participate in short design or problem-solving tasks called “Instant Challenges.”


Teams that take top place at local challenges are invited to the National KidWind Challenge. This year, almost 300 students in grades 4–12 from across the country traveled to Chicago, Illinois, for the National KidWind Challenge on May 8–10, 2018. The event, held during the American Wind Energy Association (AWEA) WINDPOWER 2018 Conference & Exhibition, hosted a total of 21 high school and 40 middle school teams competing for the chance to win the grand prize of $750, the second place prize of $500, and the third place prize of $250.



The 2018 National KidWind Challenge Champions are

High School Division:

  • First Place – Redwood Express from Bath County High School in Hot Springs, Va.
  • Second Place – Tuttle Windy’s from Tuttle High School in Tuttle, Okla.
  • Third Place (Tie) – Silver Bullet from Coachella Valley High School in Thermal, Calif.
  • Third Place (Tie) – iTurbine X from Old Donation School in Virginia Beach, Va.

Middle School Division:

  • First Place – Oxford Air Sharks from Oxford Middle School in Oxford, Kan.
  • Second Place – SPINNERS from Lanier Middle School in Fairfax, Va.
  • Third Place – The Birds from Darlington Elementary-Middle School in Darlington, Wis.

Learn more about the 2018 National KidWind Challenge and how to get involved »

All images provided by the KidWind Project.

Vernier Total Solar Eclipse Campaign Wins 24th Annual Communicator Award of Distinction

Communicator Award of Distinction 2018 Logo

The Vernier Total Solar Eclipse Campaign recently won a 24th Annual Communicator Award of Distinction in the Integrated Campaign—Business to Consumer category. The campaign was recognized for successfully demonstrating one theme through various forms of media, such as print, social media, video, and more.

With entries received from across the United States and around the world, the Communicator Awards is the largest and most competitive awards program honoring creative excellence for communications professionals. The awards are judged and overseen by the Academy of Interactive and Visual Arts (AIVA), a 600-plus member organization of leading professionals from various disciplines of the visual arts.

The multi-pronged Vernier Total Solar Eclipse Campaign celebrated last summer’s Great American Eclipse by providing tips, resources, and data that STEM teachers could use to teach students about the real-world physical phenomenon throughout the year. Examples of the data collected by educators using Vernier technology are available for free on the Vernier website. Sample data by Dave Vernier was also included in an article about the eclipse in The Physics Teacher.

In addition to the Communicator Award, the Vernier Total Solar Eclipse Campaign also won a One Planet Award and two Stevie® Awards.

Learn more about the Vernier total solar eclipse resources »

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