Bar and Scale

Both change an object’s size according to a value, but for different jobs: Bar draws a fill indicator, while Scale grows and shrinks the object itself.

Bar

Shows the value as how full a bar is. Tank level, fill, percentage — anything read as a proportion.

There are two modes: Expressions, where you compute the value in code, and Tag, where you bind straight to a variable. The form above is Tag mode.

Field	Description
Variable	The variable to read
Default Value	The value used when it cannot be read
Value Bit	Self takes the whole value; choosing a bit index reads only that bit out of the word
Is Radial	Ticked, a circular indicator is drawn instead of a bar
Minimum Value · Maximum Value	The values at which the bar counts as empty and full
Duration (s)	How many seconds a change in fill takes
Opacity	The fill’s opacity
Fill	The fill colour
From	Which edge the fill starts from — Bottom, Top, Right, Left

Set Min and Max from the real scale

The bar proportions the value between these two bounds. Give bounds that differ from the variable’s actual scale and the bar fills early or never fills at all — an indicator that looks right and reads wrong.

From is not only a visual preference: Bottom reads naturally for a tank, Left for a horizontal fill gauge. The wrong direction invites the operator to read the indicator backwards.

Deciding the fill settings at run time

Bar is one of the two types that can take its visual settings at run time (the other is Pipe). In Expressions mode, when the expression returns an object instead of a plain number, the fields on that object are used in place of the form’s settings. Detail: Element Editor.

Scale

Grows or shrinks the object itself with the value. It is used to make an indicator draw attention by growing, or to size a symbol by the flow through it.

Field	Description
Variable	The variable to read
Default Value	The value used when it cannot be read
Value Bit	The whole value, or a single bit of it
Minimum Value · Maximum Value	The values the ends of the scaling correspond to
Horizontal · Vertical	Which axis to scale on — either or both
Origin-X · Origin-Y	The point the scaling is measured from

The Origin fields are where most of the mistakes are: the default point is the object’s corner, so the object appears to drift in one direction as it grows. To have it grow from its middle, move the origin to the object’s centre.

Which to use

What you want	Type
To show how full a level is	Bar
A circular fill gauge	Bar with Is Radial
The object itself to grow and shrink	Scale
A time series with axes	Chart

Related

• Element Editor — the fields every binding form shares
• Rotate and Move — rotating and translating an object