Resist! is a resistor calculator. It can decode resistor colour bands for four or five-band components. To select the type of resistor, tap the "4" or "5" button at the top of the screen.
Then tap the colours of the resistor's bands. Use the four or five displayed lists in a clockwise fashion: the small list at the bottom right is for the resistor's last band (the tolerance band — this is distinguished as the ‘last’ band by being slightly further away from the others). Tap a colour and the resistance and tolerance at the bottom of the screen will update.
You can also write a numeric value and Resist! will show the band colours on the lists.
X button appears to indicate a syntax error in specifying resistance (Resist! understands both engineering and scientific notations), or if the value entered does not exist in the currently selected resistor E series.
Press on the
X button and the closest available value will be automatically selected.
The E series restrict resistance values to a small set of preferred values. Use the popup at the top right corner to select the E series you're using, or choose ‘Free’ if you don't want approximations and warnings about preferred values.
You may configure the program to display resistances in either scientific or engineering notation. Engineering style shows resistance values like
4R7, meaning 4.7Ω and
4K7, meaning 4,700Ω. Scientific notation displays
Regardless of what is set-up as the program's display style, you can always write resistances in any of the two modes.
The E series are used for stocking purposes and restrict the possible resistance values to a usable minimum. The commonest series are the E3, E6, E12 and E24. E48 and E96 also exist but aren't used very much so Resist! doesn't support them yet. Series E3 has three values for each decade: 1.0, 2.2, and 4.7. This means that E3 resistors are available in 1R, 2R2, 4R7, 10R, 22R, 47R, 100R, 220R, 470R, 1K, 2K2, 4K7, et cetera.
E6 adds three values, allowing 1.0, 1.5, 2.2, 3.3, 4.7 and 6.8.
E12 doubles that, allowing 1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2.
E24 provides values for 1.0, 1.1, 1.2, 1.3, 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.7, 3.0, 3.3, 3.6, 3.9, 4.3, 4.7, 5.1, 5.6, 6.2, 6.8, 7.5, 8.2, 9.1.
Please note that the values are not checked against lists of what E-series resistors are actually produced, only against what is defined as correct usage according to the standard. For instance, E12 usually only offers resistors up to 1MΩ, but Resist! will still allow you to specify a 2M7 resistance.