Troubleshooting

How to Measure the Output of an Electrochemical Oxygen Sensor Using a Digital Multimeter

Learn how to measure the output of an electrochemical oxygen sensor in ambient air using a digital multimeter, verify proper sensor output, and compare the measured output against the specification for your sensor model.

Objective: A step-by-step guide to help you measure the output of your industrial electrochemical galvanic micro-fuel cell oxygen sensors.

Tools Needed

  • Multimeter capable of measuring micro-Amp (µA) DC current (i.e. Fluke 87 III)
  • Test leads

Step 1: Set Up and Multimeter Configuration

If you are not getting a reading or are experiencing inconsistencies of your electrochemical oxygen sensor, first ensure your testing equipment is set up correctly:

  • Confirm your multimeter is powered on and has sufficient battery life.
  • Check that the selection dial is set to the current measurement (µA) setting.
  • Check that you are reading DC current; some multimeters are preset to AC.
  • Ensure the positive (red) test lead is firmly plugged into the current terminal (µA).
  • Ensure the negative (black) test lead is firmly plugged into the COM terminal.
multimeter-reading
Multimeter dial set to the µA DC current range, with test leads correctly connected.
sensor-contact-test
Negative (black) lead on the middle contact, positive (red) lead on the outer contact.

Step 2: Checking Output Reading on Sensor​

  • Verify the sensor is placed on a flat surface with the PCB side facing up.
  • Ensure any shorting tab or residue is wiped off the PCB board to avoid shorting.
  • Ensure the negative (black) lead is making direct, steady contact with the middle sensor contact.
  • Ensure the positive (red) lead is making direct, steady contact with the outer sensor contact.

Step 2A: 0.00 Output Reading

If your multimeter displays 0.00, the sensor is likely dead. Contact technical support for a replacement or further evaluation.

Step 2B: Negative Output Reading

  • If your multimeter displays a negative value, the polarity of your test leads is probably reversed.

    • Remove both test leads from the sensor contacts.
    • Reconnect the negative (black) lead specifically to the middle contact.
    • Reconnect the positive (red) lead specifically to the outer contact.

Step 2C: Unstable Output Reading

If your multimeter shows an unstable output, the sensor is likely damaged. Contact technical support for a replacement or further evaluation. Output should stabilize within 60 seconds.

Step 2D: Addressing Out-of-Specification Readings

If the output reading does not fall within the acceptable tolerance specifications for your specific sensor model, contact technical support for a replacement or further evaluation. (Output specifications by sensor model are listed below.)
A stable, positive µA reading confirms the sensor is producing output.

Step 3: Safe Storage Practices

To prevent degradation after your testing is complete, verify your storage steps:
  • Place a red shorting tab (or any shorting tab) across the PCB; make sure that it touches both the inner (negative) and outer (positive) contacts. This will short out the open circuit.
  • Store the sensor in an appropriate low-ingress or antistatic bag.  Purge the bag slowly with nitrogen or another inert gas and seal the bag.
sensor-shorting-tab
A shorting tab placed across both contacts prevents degradation during storage.

Output Specifications by Sensor Model

Class Sensor Type Output Specs
Trace (PPM)TO2-1x285 – 590 µA
Trace (PPM)TO2-2x285 – 590 µA
Trace (PPM)TO2-133520 – 1020 µA
Trace (PPM)TO2-233530 – 1050 µA
Trace (PPM)TO2-238530 – 1050 µA
HybridTO2-19285 – 590 µA
PercentPO2-1x245 – 430 µA
PercentPO2-16038 – 74 µA
PercentPO2-2438 – 74 µA
PurityPO2-112038 – 74 µA
Click a sensor model to view its full product page and datasheet.
Note: Output specs are described as the output in ambient air (20.9%) at sea level and 25°C.

Why Measure Sensor Output?

Measuring the output current of an electrochemical oxygen sensor is a quick way to verify that the sensor is producing a normal, stable signal before installation or during troubleshooting. This test is commonly used for incoming inspection, field service, and diagnosing analyzer problems.
Important Notes:
  • Output specifications are based on ambient air (20.9% oxygen), sea level, and 25°C.
  • Sensors tested at higher elevations will produce proportionally lower output because the oxygen partial pressure is lower.
  • Allow the sensor to stabilize before recording the final reading (typically 45 – 60 seconds).
  • Always compare the measured output to the published specification for your sensor model.

Frequently Asked Questions

The sensor has likely reached end of life or has been damaged.  Alternative check your meter and make sure it is hooked up and functioning properly.

The meter leads are most likely reversed. Connect the black lead to the center contact and the red lead to the outer contact.

Poor electrical contact, a damaged sensor, or insufficient stabilization time may cause fluctuating readings.  Often if a sensor has seen a pressure issue outside of the specifications (vacuum or excess pressure) it can damage the membrane and make the sensor unstable.

No. These sensors should be checked by measuring their output current (µA DC).

Need Assistance?

If your sensor does not fall within the published output specification, contact Southland Sensing Technical Support. Our engineers can help determine whether the issue is the sensor, the analyzer electronics, or the sampling system.
Contact Support →