Indoor illuminance chart card

Who it’s for

Facility managers, building automation engineers, and workplace managers ask “what is the illuminance in this space right now, and how has it varied across the day?” They need both the current reading and the trend to validate that the lighting control system is dimming and brightening at the right times.

What it does

A sensor reporting illuminance = 350 lx shows the current value color-coded by band alongside a time-series chart of recent readings: dark gray for Dim (0–100 lx), orange for Low (100–300 lx), dark orange for Moderate (300–500 lx), and red for Bright (above 500 lx). The chart lets building engineers see whether the lighting profile matches the occupancy schedule.

• Live illuminance reading in lx with color coding across four bands
• Historical trend chart shows how illuminance has evolved over the selected time window
• Shows one sensor’s data per widget; add multiple widgets to monitor different zones

How to set up

Data keys

Key	Role	Type	Description
illuminance	Chart series	Timeseries	Illuminance in lx; change the key name to match your device’s telemetry key
Latest	Latest value	Timeseries	The headline figure above the chart. Its own color ranges are where the band colors are edited
Delta percent	Percentage change	Timeseries	Change against the previous period, as a percentage
Delta absolute	Absolute change	Timeseries	Change against the previous period, in the key’s own unit

The widget ships with a simulated function datasource key labeled Illuminance, so it draws random values until you point the datasource at a device and rename the key.

To point it at your own device: open the dashboard in edit mode, open the widget’s Datasources, pick the entity or entity alias, and replace the function key with the key your device reports.

Value ranges

Range (lx)	Level	Color
0–100	Dim	Dark Gray
100–300	Low	Orange
300–500	Moderate	Dark Orange
500+	Bright	Red

How to customize

• To change the time window — adjust the dashboard time filter to show the last hour, day, or week of illuminance readings.
• To change the band thresholds — open the widget settings and adjust the boundaries to match your space’s lighting standard.
• To change the chart colors — edit the color of each range on the Latest data key.

Tips

• A 24-hour chart captures the full lighting profile: the ramp-up at the start of the working day, the contribution of daylight during sunny periods, the cutback when occupancy sensors register an empty room, and the overnight dim — deviations from this expected pattern pinpoint control faults.
• Illuminance readings that track the solar angle (rising in the morning, peaking at noon, falling in the afternoon) in a north-facing office indicate the daylight sensor is misconfigured and treating reflected indirect light as direct sunlight.
• For lighting energy audits, compare the illuminance profile against the occupancy log to quantify how much time lights were on at full output in an empty room.