What the Averaging Object Is
The Averaging object, defined in Clause 12.5 of ANSI/ASHRAE 135-2024, watches one property on a BACnet device and continuously reports the minimum, maximum, and average of its value over a sampling window. Instead of a single instantaneous reading, it gives the head end (the central BMS server) a statistical summary of how a value behaved across a recent span of time.
Object_Property_Reference names the property being sampled, Window_Interval and Window_Samples define the length and resolution of the window, and Minimum_Value, Maximum_Value, and Average_Value report the computed statistics. Writing any of the window or sampling properties resets the buffer and restarts the calculation. The Averaging object does not support intrinsic reporting and applies no event algorithm; it is purely a monitoring and statistics object.
Where You’ll See It
- Performance monitoring. An Averaging object tracks a space temperature or duct pressure to reveal the range and mean over the last window, exposing swings a single snapshot would hide.
- Peak capture.
Maximum_Valuerecords the highest value seen in the window, useful for catching brief demand or pressure spikes. - Commissioning and diagnostics. A technician points an Averaging object at a control variable to confirm a loop is holding its setpoint without excessive oscillation.
Required Properties
Clause 12.5 requires every Averaging object to provide these properties. Datatypes are the spec’s names: REAL is a floating-point number, Unsigned an integer, and the BACnet-prefixed types are structured values defined by the standard. Attempted_Samples, Window_Interval, and Window_Samples are writable (marked below); writing any of them clears the buffer and restarts the calculation.
| Property | Datatype | What it holds |
|---|---|---|
Object_Identifier | BACnetObjectIdentifier | The object’s type and instance number, unique within the device |
Object_Name | CharacterString | The human-readable point name, unique within the device |
Object_Type | BACnetObjectType | Always averaging for this object |
Minimum_Value | REAL | The lowest sampled value in the current window |
Average_Value | REAL | The average of the sampled values in the current window |
Maximum_Value | REAL | The highest sampled value in the current window |
Attempted_Samples | Unsigned | Writable; the number of samples taken in the window, and writing it resets the calculation |
Valid_Samples | Unsigned | The number of samples that were valid (contributed to the statistics) |
Object_Property_Reference | BACnetDeviceObjectPropertyReference | The property being sampled |
Window_Interval | Unsigned | Writable; the length of the sampling window in seconds |
Window_Samples | Unsigned | Writable; the number of samples taken across the window |
Property_List | BACnetARRAY[N] of BACnetPropertyIdentifier | The list of properties this instance actually implements |
Optional Properties
The optional set is small. Minimum_Value_Timestamp and Maximum_Value_Timestamp record when the extremes occurred, and Variance_Value reports the statistical variance across the window when the device computes it.
| Property | Datatype | Group |
|---|---|---|
Description | CharacterString | General |
Minimum_Value_Timestamp | BACnetDateTime | Value range |
Maximum_Value_Timestamp | BACnetDateTime | Value range |
Variance_Value | REAL | Value range |
Audit_Level | BACnetAuditLevel | Auditing |
Auditable_Operations | BACnetAuditOperationFlags | Auditing |
Tags | BACnetARRAY[N] of BACnetNameValue | Tagging and profile |
Profile_Location | CharacterString | Tagging and profile |
Profile_Name | CharacterString | Tagging and profile |
Related Objects
- Trend Log: records a property’s full history over time, where the Averaging object keeps only the running min, max, and average.
- Analog Input: a typical monitored value an Averaging object samples.
- Loop: a control loop whose behavior an Averaging object can characterize.
What Chipkin Provides
The Averaging object is modeled in the CAS BACnet Stack and served with its statistics properties; the windowed min, max, and average computation is object behavior the device supplies. Talk to us about modeling your device’s points.