To understand what Wraparound Mode does, it’s important to grasp the concept of how a data logger behaves under normal circumstances.
MadgeTech 4 provides an estimate on how long it will take the memory of a data logger to reach full capacity based on the selected reading interval. This is known as the ‘Log Time’. The Log Time can be found in the Custom Start menu in the top right corner, and depending on the selected Reading Interval, the Log Time will grow larger or smaller.
When recording with Custom Start, the data logger will record data to it’s memory at the given interval until the memory is full.
Custom Start: Wraparound Disabled
Once the internal memory is full, the data logger will stop recording. All of the data from the start of the recording until the very end will be retrievable via the Download command. Once the data has been downloaded, Custom Start can be used to start a new recording.
Real Time Recordings and Custom Start: Wraparound Enabled
Once the internal memory is full, the data logger will continue to record data. Because the memory of the data logger is full, it will begin overwriting the earliest data points available, starting with the first reading the data logger recorded to memory, before progressing to the second, third, and et cetera. In other words, data is written on a first-in, first-out basis (FIFO).
While the earliest data is permanently erased in this process with each additional reading, this allows the data logger to record data until it is otherwise manually interrupted. For Real Time recordings, the wraparound feature is always on, and cannot be disabled.
Wraparound: An Analogy
In certain businesses, it’s important to have security cameras recording at all times to catch important events that may occur. Because these events can be exceedingly rare, most of the captured footage is uninteresting and will be discarded.
Instead of keeping a copy of the uninteresting footage for months or years to come, a commonly used technique is to record the new footage over the old, which erases the old footage in the process. This allows the system to keep weeks of footage for review if an event were to happen without the need to manually stop the recording, erase the old footage, and start the cameras recording again. Once an event occurs, the endless recording can be interrupted and the footage can be collected for review.
This is very similar to how wraparound works when recording data in a data logger. Older data is overwritten by new data in an endless loop until it is manually interrupted. While the data logger will always have the maximum number of readings stored in it’s memory, it will continuously forget the earliest readings to make space for the new incoming readings, until the user manually interrupts the data logger to collect data from an important event.