Applies To:
  • CitectSCADA v7.x
  • VijeoCitect v7.x 

After upgrading a v5.x/v6.x project to Citect v7.x, all the Digital trend tags are trended with a default scale of 0 - 32000. The work-around described in KB article Q1337 does not seem to work anymore. 

First note that Process Analyst is prefered and does not require any tricks to appropriately display digital trends.

KB article Q1337 is inaccurate for Citect version 7.x.
In version v7.x, Citect will use the scale of the last tag from 'TrendDigital' function. Therefore, ‘TrendDigital’ function and Trend tag definition should be modified as follow in order to assign a scale of -2 / +2 to a digital tag:

Variable Tag Name : DIGITALSCALE
Data Type : INT
Unit Name : PLC_1
Address : V498
Raw Zero Scale : -2
Raw Full Scale : 2
Eng Zero Scale : -2
Eng Full Scale : 2

‘TrendDigital’ function:



 TrendDigital(INT trendedvar, INT scalevar)

/* scalevar is not used in the function */

RETURN trendedvar; /* function return, digital value */


Trend tag definition:

Trend Tag Name : TRENDTAG2
Expression : TrendDigital( BIT_1, DIGITALSCALE)

Sample Period : 2
File Name : [Data]:TREND2
Format : #   

Trend, Scale, Digital, TrendDigital