Ranging in Fieldbus transmitters is a somewhat confusing topic due to the unfortunate names given to the diﬀerent L_Type parameter options.
Here is a list of the L_Type parameter options in FF devices along with their meanings:
Direct = the AI block will publish the signal output by the XD block, regardless of the speciﬁed OUT_Scale range
Indirect = the AI block will mathematically scale the signal from the XD block into a range speciﬁed by OUT Scale parameters using a linear equation (e.g. y = mx + b)
Indirect square root = same as above, except that a square-root function is applied to the percentage of range (useful when characterizing ﬂow transmitters based on diﬀerential pressure measurement)
More info @