Averaging

An Averaging object samples one property over a sliding time window and reports the minimum, maximum and average. It turns a noisy reading into a smoothed one without extra programming. It can sample a property on its own device or, optionally, one on another device.

Typical uses

• A 15-minute average of electrical demand
• The peak temperature over the last hour
• A smoothed pressure reading for a control loop
• The lowest flow rate in the last shift

Key properties

Property	What it holds
Object_Property_Reference	The property being sampled. It can be Boolean, integer, unsigned, enumerated or real.
Window_Interval	The length of the sliding window, in seconds.
Window_Samples	How many samples the window holds. A new sample is taken every interval divided by this count.
Minimum_Value	The smallest sample in the window.
Maximum_Value	The largest sample in the window.
Average_Value	The mean of the valid samples in the window.

How it behaves

The object is not commandable and the standard defines no event algorithm for it. Valid_Samples and Attempted_Samples show how full the window is and how many reads failed.

With the CAS BACnet Stack

Enable it with the STACK_OPTION_OBJECT_TYPE_AVERAGING build option and add each object with BACnetStack_AddObject. The stack serves the object identifier, type and property list; you provide the rest through your property callbacks.

Related object types

Analog Input, Analog Value, Trend Log

Properties

The properties ASHRAE 135-2024 clause 12.5 defines for this object type.

How to read the table:

• Conformance is what the standard asks of every object of this type: R is required, W is required and writable by a client, O is optional. A digit after the letter marks a condition in the standard that decides when the property is present or writable, such as support for intrinsic reporting.
• Present by default: yes means the stack presents the property as soon as you add the object; no means it is optional and you turn it on with BACnetStack_SetPropertyEnabled. This is the stack’s starting setup, so it can differ from the conformance code.
• Writable is whether a client can write the property by default. Change it with BACnetStack_SetPropertyWritable.
• not in profile means the stack does not offer this property for this object type.
• Value when your callback does not answer: “Held by the stack” means the stack stores and serves the value itself and does not ask your callbacks. Otherwise it is the value the stack answers when your callback declines or is not registered.

Property	Datatype	Conformance	Present by default	Writable	Value when your callback does not answer
Object_Identifier	BACnetObjectIdentifier	R	yes	no	Held by the stack.
Object_Name	CharacterString	R	yes	no	"Object <type>,<instance>", such as "Object 0,1" for Analog Input 1.
Object_Type	BACnetObjectType	R	yes	no	Held by the stack.
Minimum_Value	Real	R	yes	no	0.0
Minimum_Value_Timestamp	BACnetDateTime	O	not in profile	not in profile	No default: the read fails.
Average_Value	Real	R	yes	no	0.0
Variance_Value	Real	O	no	no	0.0
Maximum_Value	Real	R	yes	no	0.0
Maximum_Value_Timestamp	BACnetDateTime	O	not in profile	not in profile	No default: the read fails.
Description	CharacterString	O	no	no	""
Attempted_Samples	Unsigned	W1	yes	yes	0
Valid_Samples	Unsigned	R	yes	no	0
Object_Property_Reference	BACnetDeviceObjectPropertyReference	R1	yes	no	No default: the read fails.
Window_Interval	Unsigned	W1	yes	yes	0
Window_Samples	Unsigned	W1	yes	yes	0
Property_List	BACnetARRAY[N] of BACnetPropertyIdentifier	R	yes	no	Held by the stack.
Audit_Level	BACnetAuditLevel	O2	not in profile	not in profile	No default: the read fails.
Auditable_Operations	BACnetAuditOperationFlags	O2	not in profile	not in profile	No default: the read fails.
Tags	BACnetARRAY[N] of BACnetNameValue	O	no	no	No default: the read fails.
Profile_Location	CharacterString	O	no	no	""
Profile_Name	CharacterString	O	no	no	""