Calculator Tips/Classwiz

This used to be the main part of Calculator Tips, but the fx-991ex has been discontinued and its successor is...not as useful.

Note - the following are for the 991ex, NOT the 991cw. The 991cw has a very different key layout, rendering it (IMHO) much less useful for this context.

CLASSWIZ

Complex mode

For the CLASSWIZ to work with complex values, it needs to be in complex mode:

• Turn the calculator on
• Hit the Menu button
• Hit 2 for complex

To test this, try calculating the square root of negative 1. If you get a math error, you are in the wrong mode.

Other settings

• For input and output representations - you will most likely want to set the calculator to Math Input and Decimal Output. See p. 5 of the user's guide.
  • Hit Shift and then Menu/Setup
  • Hit 1 for Input/Output
  • Hit 2 for MathI / Decimal0

This will automatically convert items to floating point rather than leaving raw square roots, $$\pi$$, and the like. If you want to convert back and forth quickly, use the $$S\leftrightarrow D$$ button.

• For angles:
  • Hit shift and then Menu/Setup
  • Hit 2 for Angle Unit
  • Pick the unit you will generally be using - most likely degrees- all input and output will use these units for angles.
    • If you want to specify a different input unit during a calculation, enter the number then Option-Up-2 and choose the unit. If your calculator is in radian mode, for instance $$1\angle 45$$ will give you the result for 1 at 45 radians while $$a\angle 45^o$$ will give you the results for 45 degrees(even in radians mode).
• To display values in a particular way:
  • Hit Shift and then Menu/Setup
  • Hit 3 for Number Format
  • Sci (2) and then 5 tends to be a pretty useful way to go.
• To set the complex number display to the way you like it:
  • Hit Shift and then Menu/Setup
  • Scroll down one page and then type 2 for Complex
  • Choose either rectangular or polar coordinates

Entering Values

Cartesian

Enter the real part, followed by the sign of the imaginary part, followed by $$i$$ or $$x~i$$. Note that if the real part is negative, or if the real part is 0 and the imaginary part is negative, you need to use the unary (-) versus the binary -.

Polar

Enter the magnitude, followed by the angle symbol (SHIFT ENG), followed by the angle in the appropriate units for how your calculator is set. Note that the magnitude must be non-negative! If you have a negative magnitude for a number by itself (for instance, $$-2\angle 30^o$$, you either need to enter it as 0- that number ($$0-2\angle 30^o$$) or you need to change the angle by $$\pm180^o$$ ($$2\angle -150$$)

Displaying Values

• To show your previous answer in polar notation:
  • OPTN
  • Down
  • 1
  • =
• To show your previous answer in rectangular notation:
  • OPTN
  • Down
  • 2
  • =

Complications

• The CLASSWIZ will not accept complex numbers in polar form with negative magnitudes. You can subtract a number from another, but you can not have the unary negative in front of a magnitude.
• The CLASSWIZ will not do roots of complex numbers.

Storing Values

If you are asked to perform complex calculations, you may want to store element values so that you can simply type a letter versus entering a number every time you use those values. For example, if a problem asks you to calculate the value of:

\( \begin{align} \Bbb{H}(j\omega)=\frac{j\omega L}{j\omega L + R}\\ L=1\mbox{mH}, R=5\mbox{k}\Omega \end{align} \)

for a few different values of \(\omega\) (say, $$10$$ rad/s and $$10^6$$ rad/s), you could do the following on your calculator:

CLASSWIZ

The CLASSWIZ only has the letters A, B, C, D, E, F, x, y, and M to store, so you have to choose where to store things. For this example, we will store the inductor value in A and the resistor value in B. Also note that once you hit the STO key, you will not need to hit the ALPHA button to indicate the letter. In the keystrokes below then, the A really means hitting the (-) key and the B means hitting the...one next to it...

1 <x10x> (-) 3 <STO> A
5 <x10x> 3 <STO> B

We will store the frequency component in x:

10 * i <STO> x

to store the values. Then, to calculate the first value,

( <ALPHA> x * <ALPHA> A ) / ( <ALPHA> x * <ALPHA> A + <ALPHA> B )

and you should get $$2.0000x10^{-6}\angle 9.0000x10^1$$ Once you get the result, if you want to calculate the value for a different frequency (say, $$10^6$$), simply type

1 <x10x> 6 * <2ND> i <STO> x

then use the arrow buttons to go back up to where you performed the previous symbolic calculation, and hit the = key to recalculate. You will now get $$1.9612x10^{-1}\angle 8.8690x10^1$$.