Real-time data logger – How do they work?

Real-time is the future for data logger solutions. An intime report is valuable for decision makers during transportation.

In this article, we are going to explain how a real-time data logger works to push data online.

Building connections

We are talking about wirless connection, nowadays we have WIFI, Bluetooth, Zigbee, RF etc etc, but they are all restricted by distance. Therefor in a typical cross border real-time data logger, cellular technoloy is used for data transmission, in particular, GSM.

We build GSM moderm in every data logger, together with an embeded global sim card. Both the moderm standards and the sim card operator will decide the data connection coverage. Take Cydiance Lorca/Piura for example, the device enables a coverage of more than 160 countries, check the list here.

real-time data logger connecting cellular data base to transfer data to online platform
Temperature, humidity data transmitting through cellular base station to online platform.

You may well ask why do we not use 4G but 2G, a simple reason is 4G moderm is much more expensive than 2G, especially in our single use scenarios. There are also other cons with regards to 4G, we will write another article for this topic.

Connection exceptions

In this GSM model, the device will lose connection when there’s no base station around, for example travelling across oceans, this is a problem that basically can’t be solved. Unless we get a connection via satelite, but apparantly the cost is way too high.

Data processing and storage

We will store all data sent by the device. In a later stage(it happens normally in several seconds) the system will proceed to data filtering, duplicates removing, etc., based on some complex algorithms. Refined data will then be presented on webpages.

Data security

We encrypt all transferring data from the device and also exchanges between servers. We store data in both Alibaba and Amazon data center with enhanced security strategy to withstand external attacks.

Right temperature, right time!

Everyone understands temperature accuracy is very important for a temperature data logger. We agree and that’s why we only use NIST calibrated sensors for our products.

However we want to call attention to one specification of the temperature data loggers in this article, that most users forget or may be not awared of. That’s the time accuracy of the loggers, especially for these disposable offline USB data loggers, like our Cydiance C1.

Temperature accuracy is important. However if the times and dates registered with this accurate temperature are unaccurate, these records are then leading you to wrong impressions and reactions.

How does a data logger keep track of time?

A typical USB data logger usually runs with a button size battery. It is an isolated system with own CPU, memory and an internal clock. This internal clock, as we called a crystal oscillator, generates electrical signals at a precise frequency, which then provides the tracking of time.

Accuracy of this crystal oscillator is speced as PPM, lower PPM means higher accuracy and apparently higher cost. The temperature data logger industry leaders typically use 20PPM, while some low cost solution adopts 50PPM. In Cydiance C1, as our premium solution, we are using 5PPM.

What does this time accuracy actually mean?

Let’s make a quick math. 5PPM presents a ±5 seconds unaccuracy every 1,000,000 seconds. That means, every 30days(2,592,000 seconds), the difference will be ±12.96 seconds, and if we put it in 365 days, it will be ±157.68 seconds. that’s about 2.6 minutes.

That basically explains, you can still trust the time accuracy on C1 after the device has been placed on shelf for one year.

We haven’t considered about the environmental temperature condition in this calculation. In some cases temperature affects the crystal oscillator very much, it may amplify the difference by 4-5 times. And that’s why we insist on using a much higher component on our C1 temperature data loggers.