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Knowing what temperature, a product has been exposed to and for how long is critical in many industries. When sterilizing surgical tools or medical devices in an autoclave or heating food before canning, temperature and time should be documented. Temperature monitoring assists facility managers in legionella prevention, while environmental scientists use water temperature to assess the health of rivers and streams. Temperature data loggers can be used to monitor these and other comparable processes, as well as to obtain verification proof.
Temperature data logger fundamentals
A temperature data recorder is a type of data logger that is purpose-built to work with temperature probes or sensors (and in the case of a humidity and temperature logger, with humidity sensors too). A data logger is a type of electrical device that can record a variety of measurements. It accepts one or more sensor inputs and samples and records data at a predetermined frequency. It is frequently battery-powered. At the end of the acquisition period, the logger is recovered, and the data is downloaded to a PC for analysis. Some data recorders can even transmit measurement results to a computer or other device, eliminating the need for field trips.
Temperature data loggers are available in a wide range of shapes and sizes.
Every temperature logger consists of two components: a temperature sensor or sensors and a recording device that samples the sensor at predetermined intervals and records the measurement result. This sensor can be directly connected to the recording system or placed at a distance.
Sensor installed on the inside
Combining a thermistor or thermocouple with a logger in a single container results in a small, lightweight recording device. Its flaw is that it must be placed in the area where the temperature will be measured. Internal sensor loggers cannot be used in high-temperature situations because the electronic elements in the device must operate within a working temperature range. However, it makes them useful for documenting transport temperatures, which may be required when shipping artwork or perishable produce such as eggs.
A thermocouple is used to measure temperature.
Many temperature recorders accept direct input from one or more thermocouples. The OMEGA multi-channel HH1384, for example, is a four-channel thermometer and data logger that accepts thermocouples of the K, J, E, T, R, S, N, L, U, B, and C types. This allows temperature to be recorded close to the thermocouple data recorder, but it is not ideal when the temperature is too high or low for the batteries and electronics. Many of them are handheld devices designed for short-term recording. Several general-purpose data recorders have thermocouple and thermistor inputs, allowing them to be used as thermometers.
When employing an external probe,
The use of a temperature data logger with a probe (for example, OMEGA’s OM-CP-HITEMP140-FP is a high-temperature data logger with a flexible probe) solves the problem of obtaining measurements in too hot or cold conditions. This allows the recorder to remain in one place while the sensor is moved to another. It would, for example, allow temperature logging in an oven even if the logger itself was destroyed.
Multiple-channel temperature recorders
General-purpose and temperature data recorders with up to 32 inputs (single-ended—16 differential) are available. They will work with thermocouples and thermocouples, as well as 2-, 3-, and 4-wire RTD temperature sensors.
Getting data Many data recorders with built-in sensors are designed to look like USB drives and can be plugged into a computer’s USB port to download data. Other loggers connect via USB, but a different cable is required. Another option is to use Bluetooth® to connect the logger to a PC or even a mobile device. Some loggers can send data back to a central PC via an Ethernet network, while others communicate measurements wirelessly. Both methods eliminate the need to travel to a field data logger to retrieve the information.
Temperature measurement is essential in a wide range of applications, from monitoring the health of rivers and streams to ensuring sterilization procedures are carried out correctly. Long-term trends can only be determined by taking measurements over a long period of time in some cases. Others are curious about the highest or lowest temperature reached, as well as the duration of exposure.
Temperature and humidity recording
A record of temperature and humidity variation can be useful in identifying inefficiencies in facility management, particularly where precise measurement or temperature-sensitive operations are performed. The same is true for plant and animal propagation. A major concern for a facilities manager is the prevention of legionella, which can cause a potentially fatal form of pneumonia. In applications like these, a combination of temperature and humidity data recorders provides a time-stamped record of the experienced conditions over a long period of time.
Another situation in which a time-stamped record is useful is the transportation of artworks. In this case, simply knowing that your situation is being watched may be enough to motivate you to take extra precautions when logging at high temperatures.
While there is no strict definition of "high temperature," a high-temperature logger is a recording device designed to withstand temperatures of more than 80°C (176°F). High-temperature settings include autoclaves, pasteurization, and food and material processing. Food canning is one example. Manufacturers must demonstrate that the product has reached the minimum temperature required to kill pathogens such as botulism in this case. In such cases, loggers frequently include a probe to keep the sensitive electronics out of the heat.
Monitoring the water’s temperature
Water temperature monitoring is useful in aquariums to ensure a healthy habitat for their fish, many of which can only survive in a specific temperature range. In a similar way, scientists use the temperature of rivers and streams to assess the health of those ecosystems. Both are valid applications for a water temperature data logger, but they place different demands on the device.
Because the logger will be easily accessible in an aquarium, a large memory capacity will be unnecessary, and the data can be recovered via direct PC connection or Bluetooth. Obtaining accurate data on river temperatures, on the other hand, may require leaving the logger in place for several months. Memory capacity, battery life, and even wireless capabilities all become more important in these circumstances.
The Chain of Custody
Many foods and drugs must be shipped under tightly controlled conditions to avoid deterioration. Incorporating a small temperature data recorder into the items carried to provide a record of the conditions. This helps to ensure product integrity and provides documentation in the event of a mishandling allegation.
With so many options, it can be difficult to select the best temperature data recorder. Understanding the reasons for temperature logging allows the most important qualities to be identified and the range of available equipment to be reduced. OMEGA Engineering provides an online Data Logger Product Finder tool to assist with the process, but if you still have questions, contact OMEGA’s technical staff for advice on the best equipment for your specific application.