Since CO2 measurement can be a new parameter for some users, this article provides some basic question and answer topics related to calibration of this sensor.

How is CO2NTROL calibrated?

CO2NTROL sensors must be calibrated at two points using ArcAir software. The first is the “Zero Point”, calibrated in air or CO2-free environment such as nitrogen. The second point is the “CO2 point”, calibrated in a certified gas mixture CO2 / N2 (suggested 20% CO2 and 80% N2). During calibration, the sensor automatically controls the stability of the CO2 and temperature signals.

Why is a two point calibration required?

A two point calibration ensures the best accuracy across the entire measurement range of the dissolved Co2 sensor. CO2NTROL also has the option for a single point product calibration which may be performed after initial two point calibration during the process. If needed, the product calibration will offset the measurement value to allow it to correlate with off-line CO2 readings.

What additional hardware is needed?

You will need the following items for calibration:

  • Calibration Station (Ref 243575) shown below
  • Certified calibration gas (20% CO2 and 80% N2)
  • Flow regulator or flow meter that can control to 0.5 l/min
  • Tubing with low gas permeability

Connection hardware for ArcAir Software:

Sensor Calibration Station

Why is a flow regulator or flow meter required?

CO2NTROL measures based on the partial pressure of CO2. If the calibration gas flow rate is changing during calibration then pressure may be fluctuating as well. The result is additional error or a potential failed calibration. A simple flow regulator or variable area flow meter ensures an accurate calibration.

Below - CO2NTROL Sensor in Hamilton Calibration Station. Gas bottle with flow regulator on top

How much gas is needed for a calibration?

Approximately 4L of gas is used for each calibration. The available amount of gas should be verified prior to calibration to avoid a possible failed calibration.

Does Hamilton supply calibration gas?

Calibration gas is sourced by the end-user. We recommend contacting the same industrial gas suppliers used for other industrial processes. Examples of industrial gas suppliers include: Linde, AirGas, and PraxAir. Recently on-line vendors have begun to supply calibration gas however this may be limited to certain countries or regions.

Where is the calibration data stored?

The last calibration is stored in the CO2NTROL sensor’s embedded microtransmitter. At the end of each calibration, ArcAir offers the option to save or print the calibration report as needed for GMP compliance (FDA CFR 21 Part 11 / Eudralex 4 Annex 11). For simple confirmation, the Info tab will provide a quick view to verify if the last calibration was successful as well.

Calibration in ArcAir (Video)

The brief video below shows a step by step calibration of CO2NTROL using ArcAir software running on windows PC.

Should CO2 Be a Critical Process Parameter?

Download Part 1 of our Dissolved CO2 White Paper Series to learn how implementing real-time control of Carbon Dioxide can impact productivity at R&D and production scale bioreactors.