Why Is a Data Logger Better Than a Thermometer?

Temperature is arguably the most critical environmental variable to measure and record. This is primarily because temperature determines the rate of chemical processes, like bacterial growth, degradation of fragile vaccines, and food spoilage. It also drives physical processes like melting, boiling, and evaporation.

For this reason, sensitive temperature monitoring is an integral part of modern manufacturing, transportation, and storage. In some industries, government regulations require thorough temperature monitoring, while in others, plant operations depend on it to qualify and control processes.

Early in the 20th century, temperature was monitored by manually recording thermometer readings on paper log sheets. However, as manufacturing processes, distribution routes, and products themselves became more complex and automated, the equipment used to monitor temperature also evolved. Today, temperature in critical locations is commonly monitored using digital data loggers (DDLs).

These are compact, easy to deploy, and have greatly enhanced capabilities compared to thermometers and paper chart recorders. State of the art temperature monitoring equipment is able to measure temperature around the clock, continuously sending data to cloud-based software tools and remotely alerting support staff if a problem arises.

In this article, we’ll trace the development of data loggers, discuss some of their specific advantages over older technology, and explain why they’re an absolute must-have in certain industries.

What Is a Data Logger Exactly?

A modern data logger is a small, self-contained unit that includes a temperature sensor, data storage, data transmission, and other auxiliary elements like a power source. They’re placed in locations where temperature-sensitive operations take place, where they measure, record, and transmit temperature data.

For example, data loggers can be installed throughout a temperature-controlled warehouse, to confirm that sensitive products are being held at a safe temperature. Over time, temperature records could also be used to better understand fluctuations and cycle, to proactively improve control equipment and protocols.

Another common use for temperature data loggers is to monitor manufacturing equipment like reactors or ovens, where they confirm that material is being processed within control limits.

Evolution of Environmental Monitoring Technology

Before the development of digital temperature loggers, there were two approaches to temperature monitoring: manual thermometer readings, and paper chart recorders.

The simplest form of temperature monitoring is to manually record temperatures read from a thermometer. In some ways, this is convenient, since any type of thermometer can be used, and it involves only minimal capital investment. However, a completely manual system is also inefficient and not scalable. It would be impractical to collect data frequently using this approach, especially if there are many monitoring points scattered over a large area. Manual readings also become problematic when the thermometer is in a difficult to access location, like in a refrigerated shipping container.

Some of the inefficiencies of the manual approach can be avoided by using paper chart recorders, which record temperature on a circular chart. With a chart recorder, temperature can be collected continuously in remote locations with less human involvement. While chart recorders were a significant improvement, they have relatively high operating costs, aren’t easily automated, and aren’t designed to be scalable for growing businesses.

The microelectronics revolution of the 1980s-90s impacted many areas of technology. In the area of environmental monitoring, it allowed for the development of the DDL. The replacement of mechanical, paper-and-pen measurement and recording by microelectronics greatly reduced the operating cost of chart recorders and eliminated many of their common failure points.

DDLs also have enhanced capabilities that weren’t available in the previous technologies. For one, they have vastly increased data storage capability, since they aren’t limited by space on a paper chart.  This also makes them more compact than chart recorders, so they can be used in smaller spaces. The addition of wireless communication technology like bluetooth and WiFi means that DDLs can be deployed remotely, making them highly automated and scalable. We’ll talk more about these features in the following sections.

With these enhanced capabilities, DDLs have enabled modern processing and distribution methods. For example, in the 1970s, accurate and continuous temperature monitoring was seen as a key limiter to the distribution of childhood vaccines to remote areas. This challenge was overcome by a combination of vaccine vial monitors and digital data loggers that travel along with vaccine shipments. These loggers can continuously track temperature at the package level, confirming refrigeration has been maintained during transport, or precisely characterizing any problems that may have occurred.  

What Advantages do Data Loggers Have Over Thermometers

Next, we’ll break down four specific areas where data loggers save time and resources compared to manual thermometer readings.

First, data loggers are much better at data tracking and storage. Consider monitoring a vaccine refrigerator, where the CDC recommends collecting temperature readings at least once every 30 minutes. This would be an unnecessary burden on clinical staff when using manual thermometer readings, while a DDL does this automatically with no staff involvement. For this reason, using DDLs for vaccine monitoring is recommended by the CDC and WHO.

Some applications use even more frequent measurements, and in fact data loggers are commonly available with collection intervals down to 10 seconds. High frequency data collection is needed when temperature fluctuations can be fast, for example when doors are opened and closed in a warehouse throughout the day. This type of data is also useful for calculating the impact of temperature variations on product quality, by using the mean kinetic temperature (MTK) or other quantitative methods. In a large facility with multiple loggers, manual collection at this frequency would be impossible.

Beyond simply recording and transmitting raw data, DDLs can be integrated with software packages for conveniently visualizing and analyzing environmental data in real time.

By replacing manual paper records, the digital temperature logs generated by DDLs increase storage capacity by orders of magnitude. Also, the digital logs are automatically time-stamped and marked by location so that they can be organized and accessed later. In addition to a 30-minute recording interval, the CDC also recommends keeping monitoring records for three years, which is much more easily done with digital files.

This feature is particularly important for compliance with regulatory guidelines. There are a number of industries, like pharmaceutical manufacturing and food distribution that are regulated to follow GxP (good practices). Other industries are required to follow similar practices to achieve and maintain certifications like AS9100 for the aerospace industry. A theme in all of these is the need for complete, accurate record-keeping when it comes to temperature monitoring.  

This is exemplified by the FDA’s ALCOA guideline on data collection: attributable, legible, contemporaneously recorded, original or a true copy, and accurate. Data collected by DDLs inherently meets these criteria.

Data loggers also offer a higher level of precision. When reading from a thermometer, precision is affected by several factors, including the quality and type of thermometer. In a DDL, an electrical signal from a temperature sensor is automatically converted to real temperature, ensuring ultimate precision and repeatability. The precision of the measurement is limited only by the calibration of the sensor, which can also be tracked by integrated DDL software.

A powerful feature of modern data loggers is the ability to send alarms and notifications when a problem is detected. One simple type is an audible or visual alarm triggered when temperature goes outside of a specified range. More sophisticated systems can send notifications by phone, email, or SMS text to response personnel when a problem is detected. In this way, a well-designed alarm setup can be used to proactively address environmental control issues before an excursion takes place. This strategy would not be possible with manual temperature recording.

Why Are Data Loggers Necessary for Some Businesses

In the previous section, we talked about some of the advantages of data loggers compared to manual thermometer readings. These advantages make data loggers a must-have for businesses that operate in certain industries. Here are four reasons why:

  1. Asset protection. Thorough, accurate temperature measurement plays a critical role in protecting temperature sensitive products.

    First, a good data logger system will alert response personnel quickly if there is a temperature control problem. Second, the complete temperature record provided by a DDL is the best way to prove to customers and regulators that products were maintained within specified temperature windows.

    These come into play in a wide variety of situations, from the assembly of advanced composite materials for aerospace customers, to the shipment of medicines via a “cold chain” (a supply chain in which refrigeration is maintained end-to-end).

  2. Traceability. Data collected by a DDL can be traced back to the exact time and location it was collected. Furthermore, the calibration of the temperature sensor, which confirms its accuracy, can be traced back to a known standard kept by NIST (National Institute of Standards and Technology), the gold standard for calibration.

  3. Regulatory requirements. In some cases, the use of data loggers is specifically mandated by statute. For example, the Vaccines for Children program requires them.

    More commonly, data loggers are not called out specifically in legislation, but using them makes complying with regulations and guidance much simpler, reliable, and inexpensive.

  4. Scalability. A useful feature of a monitoring system based on remotely communicating data loggers is that it can be easily scaled up for dynamic or growing businesses. Adding new monitoring points, like a new distribution route or warehouse, is as simple as placing the loggers and adding them to the existing network in monitoring software.

    Manual thermometer readings are not scalable, since each new monitoring point involves additional time for staff to collect temperatures. 


Digital data loggers provide a much more flexible, convenient, and cost-effective means of recording temperature data compared to previous technology. They’ve evolved with the needs of a number of applications, and are a must-have for businesses operating in demanding and highly regulated industries.

For more information on state of the art temperature data logging equipment and procedures, contact the experts at Dickson.