An electronic data logger is a compact, self-contained unit that measures, records, and transmits data. Data loggers are an efficient, cost-effective way to continuously monitor temperature, humidity, pressure, and virtually any other parameter that can be measured with a sensor that generates an electrical signal. 

In other articles, we’ve taken deep dives into specific applications for data loggers, including pharmaceutical manufacturing, vaccine distribution, and other industries that are required to follow GxP (good practices), and specifically what features to consider when purchasing a data logger. One important feature of any data logger is how it transmits or exports the data it collects.

In this article, we’re going to focus on data loggers that transmit data via Bluetooth and NFC (Near Field Communications), two closely related short-range wireless technologies. These loggers are often used for remote field applications, like monitoring weather, animal habitats, soil conditions, or recording the temperature of refrigerated packages in transit. We’ll talk about why Bluetooth is used, and some other features to think about when selecting a data logger for these challenging applications. 

How do Bluetooth data loggers work?

First, some quick background. Bluetooth and NFC are both wireless, radio frequency-based communication technologies that transmit information in the ISM frequency bands (used for industrial, scientific, and medical applications). Under ideal, unobstructed conditions, Bluetooth can have a range of up to 300 feet. It can transmit through walls, but that cuts its range significantly, to 30 feet or less. NFC is designed for much shorter distances, of roughly 1.5 inches. In this article, we’ll focus on Bluetooth. NFC loggers have many of the same capabilities, but at a much shorter range. 

Newer bluetooth devices use a type of Bluetooth known as “Bluetooth low energy” (BLE, or Bluetooth Smart), which was introduced around 2010. BLE devices don’t require pairing, as older Bluetooth technology did, and use less power. 

Data loggers that are equipped with Bluetooth are normally designed to transmit data to phones, tablets, or PC’s using a proprietary app. From the app, data can be visualized directly, transferred to cloud storage, or to a data analysis package on a PC. 

A well-designed app can be a powerful tool for Bluetooth data loggers, since, in addition to simply gathering data, they can be used to track logger status and set up new loggers when they’re brought online. Apps can also have higher level functions when transferring data, like batched transfers of records from multiple loggers, or highlighting excursions or alarms on specific loggers for efficient troubleshooting.

This is a good time to mention 21 CFR Part 11. This is the federal regulation that covers electronic records, and any data logging system that is used for FDA-regulated industries should be compliant with this code. 

A key advantage to using Bluetooth for data loggers is flexibility. To illustrate this, consider two specific ways that data could be accessed from a Bluetooth logger. First- a user could periodically visit a remote logger in the field that is in a difficult to access location. Bluetooth allows the user to download the data from the logger from a distance, then take it back to an office for detailed analysis.

Second- a Bluetooth logger could be set up to transfer data to a handheld device continuously, which then transmits it to cloud-based storage, where it can be accessed from anywhere. In this way, bluetooth loggers can take advantage of advanced cloud-based monitoring software. 

Where are Bluetooth data loggers used?

The capabilities and flexibility of Bluetooth-enabled data loggers make them well suited for a number of applications. Let’s take a closer look at two classes. 

Transportation
Temperature-sensitive products, like vaccines and perishable foods, are transported via a cold chain, where refrigeration is maintained from the point of production to the customer. One way to ensure an accurate, unbroken record of temperature is to embed a logger at the package level. This can be done with inexpensive, small loggers built for this purpose.  

The logger travels with the product during all stages of transit, including particularly risky points like transfer between warehouses and shipping containers, where shipments can inadvertently be left in non-temperature controlled, unmonitored areas. When the shipment arrives at the final destination, the customer downloads the data from the embedded logger, without needing to open the package, to verify that refrigeration was maintained throughout transit. 

Outdoor environments
Bluetooth data loggers are also often used for monitoring in remote outdoor environments, for example:

• Tracking weather for climate research
• Monitoring microclimates and soil conditions to optimize fertilizer and pesticide applications for agriculture
• Automating spot checks of livestock areas to ensure health and comfort of animals
• Wildlife research
• Wetlands conservation and research
• Studying the ecological impact of industrial or infrastructure projects
• Monitoring the conditions on green rooftops

In these cases, Bluetooth loggers work well because they are able to retrieve data in difficult to access locations, and don’t require an existing wireless infrastructure to communicate. 

Note that these same advantages can be useful in indoor environments with difficult to access monitoring points and limited Wi-Fi access. 

How Does Bluetooth Compare to Other Ways of Communicating with Data Loggers?

Some of the other ways of communicating with data loggers include USB, Wi-Fi, wired ethernet, cellular, and satellite. Let’s look at how these compare with bluetooth. 

Data loggers with USB ports save data in onboard memory, for later download by physical connection via a USB cable. These function similarly to a Bluetooth or NFC enabled logger where data is periodically downloaded, with the limitation that they require a physical wired connection to be made when setting up the logger and collecting data. 

Wi-Fi and LoRaWAN (Long-Range Wide Area Network) loggers are also able to communicate wirelessly, and can upload data directly to cloud storage where it can be accessed from anywhere. However, these modes require an existing network infrastructure. For this reason, these loggers are more commonly used in indoor, fixed environments like warehouses, hospitals, and factories. Ethernet-enabled loggers have the same capability, but using a wired connection.

Another option for data loggers deployed in remote locations is to communicate via cellular or satellite connection. While this in principle allows continuous, real-time data access, there is significant additional cost associated with this type of logger. 

Compared to these other communication modes, bluetooth offers a flexible, low-cost, convenient approach that works well for remote monitoring where real-time access to data is not needed.

Other Important Considerations for Bluetooth Data Loggers Used in the Field

When deploying a Bluetooth data logger in the field, there are a few other options or features that are important to consider.

Battery Life
Battery-powered data loggers are optimized for low power consumption, and typically have battery change intervals of more than one year. If this is a concern, there are a few ways to address it. One is to use a system compatible with longer-lasting Li-ion batteries, or to supplement battery power with a solar array. Battery life can also be extended by reducing the data collection interval. 

Data Storage Capacity
This is an important spec for any logger that stores data onboard, and  is usually given as a maximum number of data points. The amount of time the logger can run without exceeding its memory can therefore be extended by reducing the data collection interval. In other words, a logger set up to collect a data point every 30 minutes can run much longer compared to one that collects one every 10 seconds.

Advanced loggers can deal with memory overloads in different ways, for example by looping back and overwriting the oldest data, or to stop recording at a predetermined date and time. 

Enclosure Protection
For data loggers that will be installed outdoors, standard rating systems have been established to quantify the protection the housing or enclosure provides against the elements. 

One is the IP (International or Ingress Protection) rating, a 2-digit code that indicates protection against solid objects (first digit) and water (second digit). Ratings range from IP00, no protection, to IP68, completely protected from dust and long term water immersion.  The other common standard that applies to monitoring equipment enclosures is NEMA (ANSI/NEMA Standard 250-2020). 

Conclusions

Bluetooth is a convenient, flexible option for data loggers deployed for remote applications, like transportation and outdoor environmental monitoring. Data transmission is streamlined and standardized, simplifying setup and data collection from difficult to access loggers. Modern web-based apps integrate data collection, visualization, organization, and transfer to cloud storage, taking advantage of the most modern monitoring tools. 

Have questions about Bluetooth-enabled data loggers or environmental monitoring? Please contact the experts at Dickson.