1 ACCEPTED SOLUTION
Accepted Solutions
Thats a strange effect, indeed and I have no explanation why Prime's dynamic unit checking thinks that the 0 seconds would be correct (sometimes).
You can get rid of it by dividing the 0 by UnitsOf(0) which is yet another miracle because UnitsOf(0) should simply yield 1 in every case but obviously sometimes yields 1 second and sometimes 1 ???
BTW, you don't even need an if statement for the calculation of PWM, as a boolean expression will yield exactly the 0 or 1 you need.
Thats a strange effect, indeed and I have no explanation why Prime's dynamic unit checking thinks that the 0 seconds would be correct (sometimes).
You can get rid of it by dividing the 0 by UnitsOf(0) which is yet another miracle because UnitsOf(0) should simply yield 1 in every case but obviously sometimes yields 1 second and sometimes 1 ???
BTW, you don't even need an if statement for the calculation of PWM, as a boolean expression will yield exactly the 0 or 1 you need.
I guess the problem only occurs when zero is in play. Prime (probably for our convience) tries to add the "proper" (?) unit to a value of zero and that seems to fail sometimes and leads to some strange effects.
Its nice that in the first example Prime adds unit Ohm to R1 and calculates the serial connection with the intended unit. The parallel circuit is left unitless !??
The alternative would be that Prime yields an error in the first example and forces its users to use consequently units even with zero values. less convenient but maybe the better approach.
From the Prime Migration Guide:
To provide more control over how numeral 0 should behave, PTC Mathcad Prime
provides two built-in constants:
• zero (lowercase) — Represents dimension less 0. For example, zero + 1m
yields an error whereas 0 + 1m = 1m
Use variable zero to ensure that the quantity is always checked for correct
dimension, even when it has a magnitude of 0.
• Zero (uppercase) — Represents 0 of any quantity. It assumes whatever unit is
required by the computation. For example, Zero*m + Zero*s = 0
Use variable Zero to simulate compatibility with legacy Mathcad treatment.
So, this is, as Werner stated above, a result of Prime's dynamic unit checking. It can, at times, make the use of "zero" somewhat less than obvious. Yours is an interesting situation, in which the zero takes on the units of the variable used in the conditional statement. However, another option is to use lowercase "zero" in the "else" statement. No, it isn't necessarily obvious, but this constant was added to Prime for just such a case. It isn't always necessary to use "zero" or "Zero", but in this case it is perhaps a slightly more aesthetically pleasing solution to your dilemma.
