Calibration Guide for the Analox Ax60+Carbon Dioxide (CO2) Sensor

The Analox Ax60+ gas detection system is designed to monitor levels of carbon dioxide (CO2), oxygen (O2) or both in areas where those or other inert gasses may bring harm to your workers. The Ax60+ ensures worker safety by alerting everyone in the area of a potential gas leak, keeping your people safe from harmful environments.

This flexible system comes with a central unit including a digital display and can offer protection in multiple areas of your environment with a choice of 1-4 sensors of either gas.

We pre-configure the unit for your local regulations making the system ready to install straight out of the box. All you need to do is follow the simple quick start guide supplied with your unit.

One of the key features of the Ax60+ is the ease of maintenance and calibration. If you own an Ax60+ unit, it’s good practice to maintain the sensor by doing a calibration proof test annually, followed by zero and span calibration if needed.

This guide will help you understand why proof tests are vitalwhy zero and span calibration is needed, and how to calibrate your Ax60+ CO2 sensors, ensuring worker safety for everyone who operates around CO2.

Top Tip! If you don’t have any of the equipment needed to do a proof test or calibration, find out who your gas provider is, they can come out and send an engineer to do the test for you.

Please note, this guide will be focusing on the calibration of the Ax60+ CO2 sensor. For more details on calibrating your Ax60+ O2 sensor, please view the service manual on page 25. A guide about calibrating an O2 sensor will be coming soon!

What does calibration of a gas sensor mean?

Technically, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Simply put, to ensure your gas monitor can detect gas levels accurately, it must first be calibrated.

When we are dealing with specific gasses, carbon dioxide in this instance, calibrating the monitor means exposing the device to a known concentration of test gas or calibration gasses for a set amount of time – this reading then becomes the reference point for future readings.

Why do gas sensors need to be calibrated?

Neglect or improper calibration can lead to inaccurate gas readings which in turn could put you and anyone else in the area in severe danger. It can also cause extra costs to the business with unnecessary downtime due to false alarms.

Calibrating your gas monitor on a regular basis helps to avoid any calibration drift that could otherwise occur, keeps accurate gas concentration readings and demonstrates that worker safety is a key priority.

Maintaining a clean air environment is key to ultimately prolonging life. If you are regularly operating in a harmful environment, both short and long term effects could prove to be extremely negative or even fatal.

How do I know if my Ax60+ CO2 sensor is giving accurate readings?

To check the accuracy of your Ax60+ CO2 sensor, you will first need to do a calibration proof test, otherwise known as a bump test. This test will be able to tell you if the sensor is reading the correct levels of CO2 in the environment or if the sensor has drifted. If the reading matches the test gas %, no action is required. However, if they do not match, the sensor will need zero and span calibration.

How often is a proof test or ‘bump test’ required?

Analox recommends that a proof test should be carried out at least once every 12 months, working at typical performance, with fixed temperatures, humidity and pressure. Adjustments may be required. This applies to both the CO2 and the O2 sensors.

If the device fails a proof test, zero and span calibration will be needed.

What is the difference between calibration and a proof test?

The main difference is that a proof test measures the accuracy of the sensor and calibration resets the sensor to ensure that it is measuring accurate readings.

How do you know when a sensor should be proof tested or calibrated?

Here is a helpful guide to show when you would need to proof test or go straight into a calibration.

Event Proof Test Calibration (zero & span)
Annual maintenance ✔️ Only if proof test fails
Sensor drift ✔️
After a high alarm ✔️
Incorrect calibration gas ✔️
Neglect of maintenance ✔️ Only if proof test fails

By using the best practice of annual maintenance with calibration proof tests, checking for drifts, and using the correct test gasses, the CO2 sensor will always give accurate readings and demonstrates that worker safety is a key priority.

How do I proof test and calibrate my Analox Ax60+ CO2 gas detector?

Analox engineers designed the Ax60+ to be calibrated by anyone, from service engineers to brewery staff. This guide will show you how simple and safe proof testing and calibration can be.

Before you start, make sure you have the following equipment ready;

  • a push-in flow adapter
  • 2-meter neoprene tubing
  • suitable 0.5-1 litres per minute regulator to fit the calibration gas bottle
  • calibration gas 3.0% carbon dioxide, balance nitrogen (for calibration proof tests and for span calibration)
  • calibration gas pure air 20.9% oxygen, balance nitrogen (for zero calibration)

Analox provides all the above equipment in an Ax60+ CO2 Check Kit, please get in contact if you wish to purchase a kit.

Finally, please check to make sure you have;

  • access to the Ax60+ central display
  • access to any Ax60+ CO2 sensor that requires testing
  • removed any splash guards that might be fitted to the sensor

Calibration Proof Test Instructions

Please use calibration gas 3.0% carbon dioxide, balance nitrogen.

  1. Ensure the Ax60+ is powered on and operating normally.
  2. Fit the neoprene tubing to the flow adaptor.
  3. Fit the flow adaptor into the aperture on the CO2 Sensor.
  4. Fit the regulator to the CO2 check gas bottle.
  5. Open the regulator valve and allow the CO2 check gas to flow across the sensor for 1 to 2 minutes. Do not block the exit of the flow adaptor.
  6. Ensure that the Ax60+ display reading is between 30000 – 30150ppm CO2. If the levels are not within the range given, follow on with a zero and span calibration.
  7. Close the regulator valve, acknowledge the alarm and ventilate the area.

Zero Calibration Instructions

Please use calibration gas pure air 20.9% oxygen, balance nitrogen, or if the area is well ventilated, you can use ambient air if you do not have access to a pure air test gas.

NOTE: A zero calibration should always be done first before a span calibration.

  1. Ensure the Ax60+ is powered on and operating normally.
  2. Press and hold Cancel + Cycle for 6 seconds to display Top-level Menu.
  3. Press Cycle four times to display Calibration.
  4. Press Accept/Test to display Zero cal.
  5. Press Accept/Test to show the Select sensor screen, and press Cycle to select the Sensor you want to calibrate.
  6. Press Accept/Test to select the Sensor. The Zero level (#) screen displays.
  7. Fit the neoprene tubing to the flow adaptor.
  8. Fit the flow adaptor into the aperture on the CO2 Sensor.
  9. Fit the regulator to the CO2 zero gas bottle.
  10. Open the regulator valve and allow the CO2 zero gas to flow across the sensor for 1 to 2 minutes. Do not block the exit of the flow adaptor.
  11. The CO2 reading on the Zero level screen will begin to reduce. Wait for the reading to stabilize.
  12. Press Accept/Test to confirm the zero calibration.
  13. If zero calibration is successful the Zero msg sent screen is displayed.
  14. Close the regulator valve.
  15. Press Cancel repeatedly to return to the system status screen

Remember to always follow a zero calibration adjustment with a span calibration adjustment.

Span Calibration Instructions

Please use calibration gas 3.0% carbon dioxide, balance nitrogen.

NOTE: A zero calibration should always be done first before a span calibration, if you have not yet done a zero calibration, please do that first.

  1. Ensure the Ax60+ is powered on and operating normally.
  2. Press and hold Cancel + Cycle for 6 seconds to display Top-level Menu.
  3. Press Cycle four times to display Calibration. Press Accept/Test to display Zero cal.
  4. Press Cycle to show Span cal., press Accept/Test to show the Select sensor screen, and press Cycle to select the Sensor you want to calibrate.
  5. Press Accept/Test to show the Span Cal Value screen.
  6. Press Cycle repeatedly to enter the span calibration value you want in 0.01% increments, or press and hold Cycle to increment the value at 0.10% increments.
  7. To reset the value and start again, repeatedly press Cycle or press and hold Cycle until you exceed 6.00 %, this will take the value back to 2.50 % and you can cycle through again until you reach the required value.
  8. Press Accept/Test to confirm the span calibration value.
  9. Fit the neoprene tubing to the flow adaptor.
  10. Fit the flow adaptor into the aperture on the CO2 Sensor.
  11. Fit the regulator to the CO2 span gas bottle.
  12. Open the regulator valve and allow the span gas to flow across the sensor for 1 to 2 minutes. Do not block the exit of the flow adaptor.
  13. The CO2 reading on the Span level screen will begin to increase. Wait for the reading to stabilize.
  14. Press Accept/Test to confirm the calibration.
  15. If span calibration is successful the Span msg sent screen is displayed.

 

Please be aware…

  • The value shown during calibration is the ‘raw’ sensor reading. When you exit the menu and return to the system status screen the value shown is a slightly elevated value.
  • Only one sensor can be calibrated at a time. To calibrate another sensor, exit the menu back to the system status screen, then repeat the calibration process for the next sensor.

 

Watch the Analox Ax60+ CO2 sensor Zero and Span Calibration

For more information, please get in touch and speak to an expert today.