4. Data Storage
Depending on your temperature recording application, you may need to only capture a few minutes’ worth of data or you may need to be able to store years’ worth of readings. You can determine the amount of data storage required by multiplying the number of channels by the sample rate and recording duration: Total Number of Points = Number of Channels × Sample Rate × Recording Duration.
When it comes to semi-permanent storage of data from a temperature monitoring system, here are some options (Figure 2):
Local memory. Many monitoring systems store recorded data on their internal memory and there are many different options for memory size. Depending on the device, there will be some sort of limit, based on the size of the internal memory. Note that some monitoring devices have no internal memory; they utilize external memory such as a USB stick or SD memory card for data storage. A good monitoring system solutions provider will be clear about local memory options and limitations.
Local gateway. Wireless temperature monitoring systems connect to gateways, which automatically collect temperature data. They may buffer it locally for later retrieval or transmit it to a PC, server, or online storage device.
Local PC. PCs remain a popular and inexpensive method for storing data. Many temperature monitoring systems come with software that allows data to be automatically downloaded and stored on a local PC.
Cloud. Cloud storage is a relatively recent capability but more and more manufacturers are offering advanced temperature monitoring systems that automatically transmit data to a server managed by the vendor. These can be free or paid services. The cloud server typically provides tools for displaying and downloading data. Other features of cloud-based systems include alarming, system configuration management, and report generation. These systems offer a convenient solution when there are multiple locations that require monitoring or when multiple users all need access to the data.
When looking at data storage options, it's also important to consider what sample rate is practical for your application. Many users initially state that they want to record data at one sample per second or faster. One problem is that it would quickly fill the available memory and lead to more frequent downloads. When you really look at the rate of temperature change of a sample stored in a refrigerator or freezer, it quickly becomes apparent that it can take minutes for the temperature to change by more than a degree. Even worse, with high-speed sampling, it becomes impractical to analyze all the data — with a sample rate of 10 Hz, one day would fill 864,000 rows in Excel.
Ultimately, you have to retrieve the data from the monitoring system and then, based on the application, you may choose to chart it, create a report, or simply archive the data in case you need it at some point in the future. Typically, the monitoring system is supplied with software that handles data display, configuration/setup, alarming, and more. In some cases, the software might come with the monitoring system or cost extra, depending on the manufacturer and model. The latest generation of devices offers Web-based software packages that only require a standard Web browser such as Chrome for configuration and data retrieval.
Just as with PC software, some interfaces are more user-friendly than others, so if you're new to data logging or your staff is required to work with the software, be sure to ask your vendor about the following features/capabilities:
Configuration — This is an area where a user-friendly interface really pays off. You want to be able to quickly move through naming sensors and setting temperature limits and sample rates.
Alarm management — Here, you choose who will receive alarms and how they'll be notified, whether over email, text message, or even landline phone calls with some models.
Data retrieval — You'll want to be able to retrieve your data as quickly and easily as possible and intuitive software really helps here.
Charting — Useful for identifying and displaying data trends such as temperature profiles or spikes. Many software packages also generate and print reports.
Report generation — The ability to easily generate compliance reports may be necessary for FDA or other regulatory bodies.
For most temperature monitoring applications, alarming — the capability to alert someone, somehow, whenever the programmed limits are reached — is a core requirement. As noted above, alarms can be local, where you have to be in the vicinity of the system to be alerted or they can be remote, allowing you to be notified wherever you are. Another feature to look for is a watchdog alarm to send a message if the system ever goes offline or if there is a power outage. Functions like this are critical when the product being monitored is irreplaceable.
Local alarms can consist of anything from LED indicators and buzzers to external alarm relay outputs for connection to sirens, horns, etc. More sophisticated models will automatically send you an email or text alarm to your smartphone so you're always on top of potentially critical changes in your product or process. Historically, very simple monitoring systems used a phone autodialer to provide a voice alarm but modern monitoring systems send your data directly to a secure cloud server that provides more advanced features like sequential call lists with acknowledgement verification.
Audible. If you know that personnel will be in the vicinity or if you're in no danger of losing product, an audible alarm might be enough for your purposes. Just be sure that there are no negative consequences to miss an alarm such as process delays or spoiled food. A good rule of thumb is to assume that someone might not be in the room when the alarm goes off.
Visible. As with audible alarms, first ensure that the data recorder is located somewhere with high traffic, so personnel have a fast response time.
Email. Email alerts are equally convenient, although for critical applications, you'll want to ensure that you're aware of when you're emailed — many users use their mobile devices to give them an audible when they have an incoming alarm e-mail.
SMS. SMS text alerts are a popular way to get an instant heads-up on alarm events. Once configured, the temperature monitoring system will automatically send alarms out to specified personnel.
Phone. Some systems provide dial-out capability, enabling immediate notification virtually anywhere. There are systems that support both batch and sequential call lists and customizable lists to allow each probe to have its own set of contacts.
With this basic understanding of the different parts of a temperature monitoring system, you're now informed enough to think about how you want to get your data and how you want to work with it. This is a great place to start contacting solution providers and seeing products and feature lists.
Post-installation, you should start seeing benefits in the form of reduced product loss, lower operating process costs, greater vendor reputation, or whatever your specific needs are.
This article was contributed by CAS DataLoggers, Chesterland, OH. For more information, visit here .