Differential scale
Synonym  Linear differential scale 

Definition  A scale that contains numerical values after subtraction between two values of the same kind 
Description 
Numerical values on a differential scale can be subjected to subtraction and addition, but not division or multiplication Note: An absolute zero point does not exist 
Value set 
Numerical values between negative infinity and positive infinity (∞ – ∞) Note: The low and high limits of reportable result ranges are defined for each measurand 
Example of values 
Temperature of Mr. Smith’s body is 37 °C Base excess of Mr. Smith’s arterial plasma is 5 mmol/L 
Mathematical operations 
a+b: Two values of same measurand can be added ab: Two values of same measurand can be added Note: “a” denotes a value at a time point. “b” denotes a value at a different time point than “a”. Example Change of base excess of Mr. Smith’s arterial plasma (Base excess (day 2) – Base excess (day 1)) is +10 mmol/L 
Reference 
