Tip 89. Coefficients for units
Fig. 89. Coefficients
for units of measure
The system
of measure of physical values that is built-in in Mathcad is rather illogical.
For example, in this program there are km, cm and mm
(kilometer, centimeter and millimeter), but there are not units divisible by
Pascal – unite of measure of pressure (kPa, MPa and etc.), though Pascal (Pa, Newton by square meter) is used very seldom without factors. Because of
it user of Mathcad has to introduce auxiliary (user’s) units of measure of
pressure (kPa := 103 Pa[1], ÌPà := 106 Pà and
etc.) and other physical values (ms := 10-3 sec and etc.). This problem can be solved if we introduce coefficients
divisible by ten (see fig. 89) but not new units of
measure. After it if we change unit of measure that is printed in addition to
dimensional value (see tip 4) or during
input of unit of measure we can put in multiplication of the factor on
built-in unit, pouring them together (k×Pa ® kPa and
etc.) by change of the multiplication sign (see the dialogue windows in the fig. 89)
to absentee blank (No Space).
With
help of this advise, running counter to tip 9,
where was said that never it is worth to leave out the sign of multiplication
we find new question: what does it mean mm? – it is millimeter or square mater (m×m, where product point (×) is changed to absentee blank). Indeed such ambiguous interpretations
meet not only in Mathcad: mkg – what does it mean? – it is microgram (mk×g) or millikilogram (m×kg)
i.å. gram. Here it is better to write mg
and everything will be clear. Kilogram is enough strange unit: it is one in
“magnificent seven” SI (International System of Units) that is formed by form
but united (main) by matter.
Remark. The problem of mm (see above) can be solved if we choose different styles for the
first and second letter m (see tip 52): the first m is user’s constant 10-3
but the second one is built-in unit of measure of length (meter)[2].