Matter Specification - Illuminance Measurement Cluster

Matter :: Illuminance Measurement Cluster

The Illuminance Measurement cluster provides an interface to illuminance measurement functionality, including configuration and provision of notifications of illuminance measurements.
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1. Classification

Hierarchy	Role	Scope	PICS Code
Base	Application	Endpoint	ILL

2. Identifier

Identifier	Name
0x0400	Illuminance Measurement

3. Data Types

3.1. LightSensorTypeEnum

Value	Name	Summary	Conformance
0	Photodiode	Indicates photodiode sensor type	M
1	CMOS	Indicates CMOS sensor type	M
64 to 254	MS	Reserved for manufacturer specific light sensor types	O

4. Attributes

4.1. Measured Value

ID	Name	Type	Constraint	Quality	Default	Access	Conformance
0x0000	MeasuredValue	uint16	0, MinMeasuredValue to MaxMeasuredValue	PX	0	R V	M

The MeasuredValue attribute represents the illuminance in Lux (symbol lx) as follows:

• MeasuredValue = \(10000 \times log_{10}{(illuminance)} + 1\)

where 1 lx <= illuminance <= 3.576 Mlx, corresponding to a MeasuredValue in the range 1 to 0xFFFE.
The MeasuredValue attribute can take the following values:

• 0 indicates a value of illuminance that is too low to be measured
• MinMeasuredValue <= MeasuredValue <= MaxMeasuredValue under normal circumstances
• null indicates that the illuminance measurement is invalid.

The MeasuredValue attribute is updated continuously as new measurements are made.

4.2. Min Measured Value

ID	Name	Type	Constraint	Quality	Default	Access	Conformance
0x0001	MinMeasuredValue	uint16	1 to MaxMeasuredValue-1	X		R V	M

The MinMeasuredValue attribute indicates the minimum value of MeasuredValue that can be measured.
A value of null indicates that this attribute is not defined. See Measured Value for more
details.

4.3. Max Measured Value

ID	Name	Type	Constraint	Quality	Default	Access	Conformance
0x0002	MaxMeasuredValue	uint16	MinMeasuredValue+1 to 65534	X		R V	M

The MaxMeasuredValue attribute indicates the maximum value of MeasuredValue that can be measured.
A value of null indicates that this attribute is not defined. See Measured Value for more
details.

4.4. Tolerance

ID	Name	Type	Constraint	Quality	Default	Access	Conformance
0x0003	Tolerance	uint16	0 to 2048			R V	O

See Measured Value.

4.5. Light Sensor Type

ID	Name	Type	Constraint	Quality	Default	Access	Conformance
0x0004	LightSensorType	LightSensorTypeEnum	all	X	null	R V	O

The LightSensorType attribute specifies the electronic type of the light sensor. This attribute SHALL
be set to one of the non-reserved values listed in LightSensorTypeEnum or null in case the sensor
type is unknown.

5. Measured Value

5.1. Constraint

Where MinMeasuredValue or MaxMeasuredValue attributes are mandatory the null value MAY be used to indicate that a limit is unknown.

For any measurement cluster with MeasuredValue, MinMeasuredValue and MaxMeasuredValue attributes, the following SHALL be always be true:

• If MinMeasuredValue and MaxMeasuredValue are both known, then MaxMeasuredValue SHALL be greater than MinMeasuredValue.
• If MaxMeasuredValue is known, then MeasuredValue SHALL be less than or equal to MaxMeasuredValue.
• If MinMeasuredValue is known, then MeasuredValue SHALL be greater than or equal to MinMeasuredValue.

5.2. Tolerance

For any measurement cluster with a MeasuredValue and Tolerance attribute, when Tolerance is implemented the following SHALL always be true:

• The Tolerance attribute SHALL indicate the magnitude of the possible error that is associated with MeasuredValue attribute, using the same units and resolution. The true value SHALL be in the range (MeasuredValue – Tolerance) to (MeasuredValue + Tolerance).
• If known, the true value SHALL never be outside the possible physical range. Some examples:
  • a temperature SHALL NOT be below absolute zero
  • a concentration SHALL NOT be negative