There are three system variables that contribute to the display of linetypes in AutoCAD/ADT:
- LTSCALE is the "LineType SCALE" factor; it is applied globally to the linetype definition of all entities.
- PSLTSCALE is the "Paper Space LineType SCALE" system variable and it controls the display of linetypes in a Layout tab. There are two choices: use 0 if you do not want the viewport magnification factor to be applied to linetypes within that viewport; use 1 if you do.
- CELTSCALE is the "Current Entity LineType SCALE" and is the default entity line type scale applied to newly created entities. The setting of this variable only affects newly created entities; previously created entities entity scale factor is stored in their entity data and can be checked/changed in the Properties dialog. In my opinion, the variable should always be set to 1 and, unless there is an extremely good reason to do otherwise, the value should be kept at 1 for all entities. This setting has no impact on the Model tab vs. Layout tab linetype display issue, and is included only for completeness.
What settings to use for LTSCALE and PSLTSCALE will vary, depending upon how you use layouts. If all of your viewports [or if you only ever have one viewport] in your Layout tabs are the same relative scale and you never have any linetypes applied to objects in paper space, then you can set PSLTSCALE to 0 and LTSCALE to whatever you would set in the Model tab.
I rarely have that situation, so my standard way of setting up a drawing is to have PSLTSCALE set to 1. My Layout tabs are all set up to plot at full size [1:1], so when in a Layout tab, LTSCALE is set to the value I would use for full size plotting [our office standard is 0.375; other offices use 0.5 or 1.0]. On those rare occasions when I work in the Model tab, LTSCALE is set to the value based on my current "editing" scale [the intended plot scale of the area I am working on at that time]. For my office that is 0.375 times the editing scale factor, so for 1/8" = 1'-0", I would use 36. [Other offices would use 48 or 96.]