How Temperature Sensor Drift Can Affect Pasteurisation
In food and dairy manufacturing, temperature is often more than just another process measurement. It can be a critical part of controlling a process, maintaining product consistency and demonstrating that the required conditions have been achieved. Pasteurisation is a good example. The process relies on temperature measurement to provide operators and control systems with information about what is happening within the process. If that measurement isn’t accurate, the problem isn’t necessarily with the pasteuriser itself. It may be with the instrument being relied on to measure it.This is where temperature sensor drift can become an operational concern.
What is temperature sensor drift?
Temperature sensors and associated instrumentation can change in performance over time. The amount of change may be small, gradual and difficult to detect simply by looking at the reading on a control system. The instrument may still be producing a temperature value. The PLC may still be receiving a signal. The HMI may still be displaying a number.
But the question is whether that number is still accurate enough for the process. Drift can be influenced by factors such as operating conditions, temperature cycling, ageing, mechanical damage and the environment in which the instrument is being used. For a manufacturer, the challenge is that measurement drift isn’t always obvious until the instrument is checked against a suitable reference.
Why does this matter during pasteurisation?
Pasteurisation processes depend on controlled temperature conditions. The temperature measurement is therefore part of the information used to understand and control the process.
If a sensor is reading higher or lower than the actual process temperature, the control system is working with an inaccurate measurement.That can affect how the process is monitored and how operators respond to what they are seeing. The important point is that the sensor doesn’t necessarily have to fail completely to become a problem. A sensor that continues to operate but has moved outside its required tolerance can create uncertainty around the measurement. For manufacturers, that uncertainty matters.
Calibration helps identify measurement drift
Regular calibration provides a way to check whether a temperature instrument is continuing to perform within the required parameters.The instrument is compared against a known reference at defined temperature points, with the results recorded. This provides an evidence-based view of how the instrument is performing rather than relying on the fact that it is still producing a reading. If the instrument is found to be outside tolerance, the manufacturer can then investigate what action is required. Depending on the application and the cause, that may involve adjustment, repair or replacement. The calibration result can also form part of the wider record for the instrument, providing traceability of its performance over time.
Calibration needs to reflect the application
Not every temperature measurement in a food manufacturing facility has the same level of importance or the same calibration requirements.A probe used within a critical process may have different tolerances and testing requirements from an instrument used for general environmental monitoring.The way an instrument is installed can also influence how it needs to be tested. This is why calibration shouldn’t be treated as simply taking a probe out, checking it against a reference and putting it back. The instrument, its installation, the required tolerance and the process it supports all need to be considered. BONNER’s approach to calibration is based on understanding that wider application.Our team works across food, beverage and dairy manufacturing environments, combining calibration expertise with wider instrumentation and automation knowledge.
A real example: calibrating temperature measurement at Pilgrims
BONNER’s work with Pilgrims Carrickmacross demonstrates why a practical approach to temperature calibration matters.The site needed temperature probes to be calibrated at three test points, with a defined tolerance of ±0.5°C. The probes were relatively short and had a large thread, which meant a standard dry-block approach wasn’t suitable for the application. Rather than treating this as a straightforward calibration exercise, BONNER developed a solution around the physical characteristics of the probes and the requirements of the process. The probes were calibrated using a stirred liquid temperature bath, allowing the probe and thread to be fully immersed and reducing the potential influence of ambient conditions. The work also went beyond checking the probe itself. The signal was tested through to the PLC and the resulting reading checked against the HMI, allowing the complete measurement loop to be verified.
What happens when a temperature sensor is outside tolerance?
Finding an instrument outside tolerance doesn’t automatically mean that the entire process has failed. The next step is to understand the result.How far outside tolerance was the instrument? When was it last calibrated? What process was it measuring? How critical was that measurement? Has the instrument been adjusted, repaired or replaced? Does the result require further investigation? These questions are particularly important where the instrument is associated with a critical food processing step.
A well-managed calibration programme gives engineering and quality teams the information they need to investigate these situations rather than discovering problems only when something goes wrong.
Why on-site calibration can be valuable
For food and dairy manufacturers, removing process instrumentation from production isn’t always straightforward.Instruments can be installed directly into equipment or connected into wider control systems. Production schedules may also make extended equipment removal or downtime difficult.
On-site calibration provides an alternative, allowing instruments to be assessed within the manufacturing environment and calibration activities to be planned around the operation.
It can also allow the wider measurement system to be considered. Where a calibration result identifies an issue, having access to instrumentation and automation expertise can help manufacturers determine whether the problem sits with the sensor, the signal, the control system or another part of the measurement chain. Temperature measurement is part of the bigger picture A temperature sensor is a relatively small component within a food manufacturing process, but the information it provides can influence much larger decisions.
Calibration gives manufacturers a way to check the performance of their instruments, maintain traceable records and identify measurement issues before they become larger operational problems.
[Read the Pilgrims Carrickmacross case study →][Read how a €120 temperature sensor contributed to over €120,000 in losses →][Explore BONNER’s On-Site Calibration Services →]