Vernier Software and Technology
Vernier Software & Technology

Go Direct® ORP Sensor User Manual

Go Direct® ORP Sensor

Go Direct ORP measures the ability of a solution to act as an oxidizing agent or reducing agent. ORP stands for oxidation-reduction potential. For example, ORP electrodes are often used to measure the oxidizing ability of chlorine in swimming pools, or to determine when the equivalence point has been reached in an oxidation-reduction reaction.

Note: Vernier products are designed for educational use. Our products are not designed nor are they recommended for any industrial, medical, or commercial process such as life support, patient diagnosis, control of a manufacturing process, or industrial testing of any kind.

What's Included

  • Go Direct ORP (Go Direct Electrode Amplifier connected to a Go Direct ORP BNC Electrode)
  • Electrode storage bottle, containing pH 4/KCl solution
  • Micro USB Cable

Compatible Software

Getting Started

Please see the following link for platform-specific connection information:

Bluetooth Connection

USB Connection

  1. Install Graphical Analysis 4 on your computer, Chromebook™, or mobile device. See for software availability.
  2. Charge your sensor for at least 2 hours before first use.
  3. Turn on your sensor by pressing the power button once. The Bluetooth® LED will blink red.
  4. Launch Graphical Analysis 4.
  5. Click or tap Sensor Data Collection.
  6. Click or tap your Go Direct sensor from the list of Discovered Wireless Devices. Your sensor's ID is located near the barcode on the sensor. The Bluetooth LED will blink green when it is successfully connected.
  7. Click or tap Done to enter data-collection mode.
  1. Install Graphical Analysis 4 on your computer or Chromebook. If using LabQuest 2, make sure LabQuest App is up to date. See for software availability or to update LabQuest App.
  2. Connect the sensor to the USB port.
  3. Launch Graphical Analysis 4 or turn on LabQuest 2. You are now ready to collect data.

Charging the Sensor

Connect Go Direct ORP to the included USB Charging Cable and any USB device for two hours. Connecting Go Direct ORP to the electrode amplifier during charging is optional.

You can also charge up to eight Go Direct ORP Sensors using our Go Direct Charge Station, sold separately (order code: GDX-CRG).


Blue LED is on steady while sensor is connected to the Charging Cable or Charge Station.

Fully charged

Blue LED is off when charging is complete.

Powering the Sensor

Turning on the sensor

Press button once. Red LED indicator flashes when unit is on.

Putting the sensor in sleep mode

Press and hold button for more than three seconds to put into sleep mode. Red LED indicator stops flashing when sleeping.

Connecting the Sensor

See the following link for up-to-date connection information:

Connecting via Bluetooth

Ready to connect Red LED flashes when sensor is awake and ready to connect.
Connected Green LED flashes when sensor is connected via Bluetooth.

Connecting via USB

Connected and charging Blue and Green LED are solid when sensor is connected to Graphical Analysis via USB and unit is charging. (Green LED is obscured by the blue one.)
Connected, fully charged Green LED solid when sensor is connected to Graphical Analysis via USB and the unit is fully charged.
Charging via USB,
connected via Bluetooth
Blue LED is solid and green LED is flashing, but the green flashing LED looks white because it is overwhelmed by the blue.

Identifying the Sensor

When two or more sensors are connected, the sensors can be identified by tapping or clicking Identify in Sensor Information.

Using the Product

  1. Remove the storage bottle from the electrode by unscrewing the lid and removing the bottle and lid.
  2. Thoroughly rinse the lower section of the probe, especially around the bulb-shaped tip, using distilled or deionized water.
  3. Connect the sensor following the steps in the Getting Started section of this user manual.
  4. When you are finished making measurements, rinse the electrode with distilled water.
  5. Slide the cap onto the electrode body, and then screw the cap onto the storage bottle so the tip of the electrode is immersed in the storage solution.

Important: Do not fully submerge the sensor. The BNC connection is not waterproof.

Do not leave the electrode in acids or bases with concentrations greater than 1.0 M for periods longer than 5 minutes.

By default, the units displayed will be in mV. See to change the displayed units.

Calibrating the Sensor

Calibration of Go Direct ORP is not supported. ORP readings are in mV. The Go Direct Electrode Amplifier mV response is dictated by the amplifier (as opposed to the electrode) and does not change over time, temperature, or with the electrode being attached. Calibration of Go Direct ORP in mV by putting it into different standards does not provide a better mV calibration. It provides a worse calibration as it will assume the ORP electrode is perfect. Then the mV reading will be off regardless of which electrode is connected.


Response time

90% of final reading is one second in a buffer


–1,000 mV to +1,000 mV

Typical accuracy

± 15 mV


0.01 mV

USB specification


Wireless specification

Bluetooth 4.2

Maximum wireless range

30 m


  • EA: 8.5 cm × 3 cm × 1.75 cm
  • ORP: 15.5 cm long, 12 mm OD


300 mA Li-Poly

Battery life (single full charge)

~24 hours

Battery life (long term)

~500 full charge cycles (several years depending on usage)

Care and Maintenance

Short-term storage (up to 24 hours): Place the electrode in pH 4 or pH 7 buffer solution. It should never be stored in distilled water.

Long-term storage (more than 24 hours): Store the electrode in a pH 4 buffer/KCl storage solution in the storage bottle. The ORP electrode is shipped in this solution. Vernier sells 500 mL bottles of pH Storage Solution (order code PH‑SS), or you can prepare additional storage solution by adding 10 g of solid potassium chloride (KCl) to 100 mL of pH 4 buffer solution. Vernier sells a pH Buffer Capsule kit (PH‑BUFCAP) that includes a buffer solution preservative. Storing the electrode in this solution contributes to electrode longevity and retains electrode response time when the unit is placed back into service.

If the electrode is inadvertently stored dry for a short period of time, immerse the tip in the pH 4 buffer/KCl storage solution for a minimum of 8 hours prior to use. If the readings are still not accurate after calibration or if the response is slow, try shocking the sensor as described in the Troubleshooting section.

Battery Information

Go Direct ORP contains a small lithium-ion battery in the handle. The system is designed to consume very little power and not put heavy demands on the battery. Although the battery is warranted for one year, the expected battery life should be several years. Replacement batteries are available from Vernier (order code: GDX-BAT-300).

Storage and Maintenance

To store Go Direct ORP for extended periods of time, put the device in sleep mode by holding the button down for at least three seconds. The red LED will stop flashing to show that the unit is in sleep mode. Over several months, the battery will discharge but will not be damaged. After such storage, charge the device for a few hours, and the unit will be ready to go.

Exposing the battery to temperatures over 35°C (95°F) will reduce its lifespan. If possible, store the device in an area that is not exposed to temperature extremes.

Water Resistance

Go Direct ORP is not water resistant and should never be immersed in water.

If water gets into the device, immediately power the unit down (press and hold the power button for more than three seconds). Disconnect the sensor and charging cable, and remove the battery. Allow the device to dry thoroughly before attempting to use the device again. Do not attempt to dry using an external heat source.

How the Sensor Works

The electrode has two components: a measuring half cell comprised of platinum metal immersed in the solution in which the redox reaction is taking place, and a reference half cell (sealed gel-filled Ag/AgCl) to which the platinum half cell is referenced.

Go Direct ORP can measure redox potential in the range of –1000 to +1000 mV. Readings toward the positive region of this range indicate a strong oxidizing agent, while readings toward the negative region indicate a strong reducing agent.


Examine the glass bulb. If it is broken, ORP readings will be incorrect.

Occasionally, mold will grow in the pH 4 buffer/storage solution. Mold will not harm the electrode and can easily be removed using a mild detergent solution. Mold growth in the storage solution can be inhibited by adding a buffer preservative.

Residue on the tip of an ORP electrode can cause the readings to be noisy. To clean the electrode, use a soft cloth to wipe a small amount of ethyl alcohol or isopropyl alcohol around the globe-shaped tip of the probe. Rinse the tip with distilled water, and repeat the alcohol cleaning one more time.

For additional troubleshooting and FAQs, see

Repair Information

If you have followed the troubleshooting steps and are still having trouble with your Go Direct ORP, contact Vernier Technical Support at or call 888-837-6437. Support specialists will work with you to determine if the unit needs to be sent in for repair. At that time, a Return Merchandise Authorization (RMA) number will be issued and instructions will be communicated on how to return the unit for repair.



Vernier warrants this product to be free from defects in materials and workmanship for a period of five years from the date of shipment to the customer. This warranty does not cover damage to the product caused by abuse or improper use. This warranty covers educational institutions only.


When disposing of this electronic product, do not treat it as household waste. Its disposal is subject to regulations that vary by country and region. This item should be given to an applicable collection point for the recycling of electrical and electronic equipment. By ensuring that this product is disposed of correctly, you help prevent potential negative consequences on human health or on the environment. The recycling of materials will help to conserve natural resources. For more detailed information about recycling this product, contact your local city office or your disposal service.

Battery recycling information is available at

Do not puncture or expose the battery to excessive heat or flame.

The symbol, shown here, indicates that this product must not be disposed of in a standard waste container.

Contact Support

Fill out our online support form or call us toll-free at 1-888-837-6437.

Go to top