EE Pro for TI - 89, 92 Plus
Equations - Introduction to Equations
7
15.11 Why can't I compute a solution?
If a solution is unable to be computed for an entered problem, you might check the following:
1. Are there at least as many equations selected as there are unknown parameters?
2. Are the entered values or units for the known parameters reasonable for a specific case?
3. Are the selected equations consistent in describing a particular case (for example, the choice of certain
equations used in the calculation of diode properties depends on whether the donor density of the doping
substance Nd, exceeds the acceptor density, Na in the Semiconductors section of Solid State)
15.12 Care in choosing a consistent set of equations
The success of the equation solver in generating a useful solution, or a solution at all, is strongly dependent on the
user's insight into the problem and care in choosing equations which describe consistent relationships between the
parameters.
The following steps are suggested:
•
Read the description of each set of equations in a topic to determine which subset of equations in a series are
compatible and consistent in describing a particular case.
•
Select the equations from a subset which describe the relationships between all of the known and unknown
parameters.
•
As a rule of thumb, select as many equations from the subset as there are unknowns to avoid redundancy or
over-specification. The equations have been researched from a variety of sources and use slightly different
approximation techniques. Over-specification (selecting too many equations) may lead to an inability of the
equation solver to resolve slight numerical differences in different empirical methods of calculating values for
the same variable.
15.13 Notes for the advanced user in troubleshooting calculations
When there are no solutions possible, EE
•
Pro provides important clues via key variables eeinput, eeprob, eeans,
and eeanstyp. These variables are defined during the equation setup process by the built-in multiple equation
solver. EE
•
Pro saves a copy of the problem, its inputs, its outputs, and a characterization of the type of solution in
the user variables eeprob, eeinput, eeans, and eeanstyp. For the developer who is curious to know exactly how
the problem was entered into the multiple equation solver, or about what the multiple equation solver returned, and
to examine relevant strings. The contents of these variables may be viewed by using VAR-LINK and examining
these variables in the current session. Press
°
(
2
followed by
|
), scroll to the variable name in the
current folder and press
ˆ
to view the contents of the variable. The string may be recalled to the author line of
the home screen, modified and re-executed, if desired.
Table 15.2 Topics and Sub-topics List
1: Resistive Circuits
1: Resistance Formulas
2: Ohm's Law and Power
3: Temperature Effect
4: Max. Power Transfer
5: V, I Source
2: Capacitors, E-Fields
1: Point Charge
2: Long Charged Line
3: Charged Disk
4: Parallel Plates
5: Parallel Wires
6: Coaxial Cable
7: Sphere
3: Inductors and Magnetism
1: Long Line
2: Long Strip
3: Parallel Wires
4: Loop
5: Coaxial Cable
6: Skin Effect
4: Electron Motion
1: Beam Deflection
2: Thermionic Emission
3: Photoemission
5: Meters and Bridge Circuits
1: A, V,
Ω
Meters
2: Wheatstone Bridge
3: Wien Bridge
4: Maxwell Bridge
5: Attenuators - Symmetric R
6: Attenuators - Unsym R
6: RL and RC Circuits
1: RL Natural Response
2: RC Natural Response
3: RL Step response
4: RC Step Response
5: RL Series to Parallel
6: RC Series to Parallel
7: RLC Circuits
1: Series Impedance
8: AC Circuits
1: RL Series Impedance
9: Polyphase Circuits
1: Balanced
∆
Network
