1. User
Join Date
30.05.2013
Posts
119

## Historical Trend Scaling

Dear All,

I am having PLC variables with different limits.
I configured Historian and Created a trend with a standard template.
When I am adding the variable at run time, I am facing the problem for scaling because of different limits.
For Example, I added flow1 (Limit 0-100) , Flow2 (Limit 0-200) variables and selected the Y-axis for Flow1. Scaling will be default range of variables.
Now the trend is showing 50% value of Flow2 with respect to Y=Axis due to the range of Flow1.
Comparison of different flow variables with single trend is not possible until if we set the scale for all variables.
But If I like to compare 8 flow values then I want to know the min and max limit of all 8 variables, then i want to set scale.

For simplification, Can we able to achieve any one of the following task in Extended trend..?

1. Is it possible set the fixed scale for trend...?
For example, I fixed the scale as 0 to 200, If I add any variables at run time then the scale will be 0 to 200 for all variables.

2. I added a variable permanently and I clicked Y-axis, Now If I add the variable at run time, Is it possible to achieve the scaling of permanent variable..?

Best Regards,
A.Navaneet.

2. ## Re: Historical Trend Scaling

Hi A.Navaneet,

What about showing multiple Y-axis? The Y-Axis can be the same color as the curve and indicates the scale and limits.

When you create a new curve, the scale range is automatically taken over from the value range (Measuring range) at the variable.

Best regards,
Mark

3. User
Join Date
30.05.2013
Posts
119

## Re: Historical Trend Scaling

Dear Mark,
Yes. I know multiple Y-axis. But I would like to do the comparison with single Y-axis and common scaling.
Is it possible to do...?

Best Regards,
A.Navaneet.

4. ## Re: Historical Trend Scaling

Hi A.Navaneet,

The scale is defined for each variable / curve separately. If you want to have one common scale, you can set the scale at each curve to match the common Min. / Max. values.

One option to equalize all scales for the value with the largest range within the curve, is to use VBA to adjust the screen switch function to specify which curves should be shown, and for these curves, determine the Max. Value and Min. value for all curves, and set the Y-Scale for the Axis accordingly.

From version 7.10 there is a new feature for automatic scaling, however this is also on a per-curve basis, and not for the complete screen.

Best regards,
Mark

5. User
Join Date
30.05.2013
Posts
119

Dear Mark,