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How does the light sensor work?

In this section:

The Saga™ and the Saga-P loggers have a light sensor positioned below the display. The device measures light intensity every 10 seconds and compares the measurement to the previous one.


The logger only logs a light event to memory when there is a significant change in the light intensity between two measurements (i.e., the logger goes instantly from a completely dark environment to a bright one). Subtle changes in light intensity will not trigger a light event.

The light events are registered in the Supply Chain Monitoring (SCM) system. You will not see a light event registered on the display of the device.

The logger will only log a maximum of 6 light events to memory per hour. This is to prevent the logger from filling its memory with light events that might be triggered by a flickering light bulb or any other environmental anomaly.

Light sensor_normalbehavior_events

The image shows how light intensity changes throughout the day in a normal office environment. Red lines indicate when the device logs a light event to memory.

Why do I see two or more light-on/light-off events in a row?

To optimize memory capacity, the device does not store light events. It compares the current light intensity measurement to the previous measurement, not to the last registered event.

If you see multiple of the same light events in the web interface, it is useful to think of them as dim, dimmer, the dimmest (in case of multiple "off" events in a row); and bright, brighter, the brightest (in case of multiple "on" events in a row).