Exponentially Weighted Moving Averages (EWMAs) - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 16.0

Controller Tool Help

Brand
Johnson Controls
Metasys
Product name
Controller Configuration Tool
Document type
User Guide
Document number
LIT-12011147
Version
16.0
Revision date
2023-10-02
Language
English

Exponentially Weighted Moving Averages (EWMAs) are values for output control and data analysis, and can be used to check diagnostics. (See Tailored Summaries.) For terminal unit zone control applications, these EWMA values are shown in the Parameters tab of CCT and are available for mapping up to the Metasys UI.

Exponentially Weighted Moving Averages (EWMAs) provides descriptions of the EWMAs and the labels as they appear in CCT. The three Xs in the label relate to the type of monitored output control: zone heating (HTG), zone cooling (CLG), or flow (SAFLOW).

Table 1. Exponentially Weighted Moving Averages (EWMA) Values

EWMA

Label

Description and Definition

Absolute Error EWMA

XXX-ABSERROR

Shows how well the setpoint is maintained over time.

The Absolute Error EWMA is the absolute value of the calculated setpoint minus the present value of the controlled variable (for example, temperature or flow). These values are calculated in the units of the controlled variable. The moving average calculation for this value is performed at the effective period of the PID.

Example: If this value increases in reference to the type of loop under control, the increase may indicate a control or mechanical system issue.

Absolute Effort EWMA

XXX-ABSEFFORT

Shows whether output devices are being exercised excessively.

The Absolute Effort EWMA is the absolute value of the change in the present value from one execution of the PID to the next. These values are calculated as percentages. The moving average calculation for this value is performed at the effective period of the PID.

Example: If this value increases more than 5 to 10%, the increase may indicate excessive controlled device movement.

Error EWMA

XXX-ERROR

Indicates whether you are above or below the error as above or below the setpoint.

The Error EWMA is the controlled variable setpoint minus the present value of the controlled variable. These values are calculated in the units of the controlled variable. The moving average calculation for this value is performed at the effective period of the PID.

Example: If this value increases or decreases in reference to the type of loop under control, the value change may indicate a control or mechanical system issue. If a loop is cycling above and below its setpoint, the XXX-ERROR value tends to be close to zero, which is why we recommend using the XXX-ABSERROR value instead.

Present Value EWMA

XXX-EWMA

Indicates the average PID controller output.

The Present Value EWMA is the average position of the PID present value. These values are calculated in percentage. The moving average calculation for this value is performed at the effective period of the PID.