Re: who uses programmable calculators? Message #16 Posted by Fred Lusk on 18 June 2013, 1:13 a.m., in response to message #1 by John Ioannidis
I am a professional civil engineer with 33 years of experience. I use my HP-42S every day and sometimes my HP-48G+ or my HP-41CX. I also use emulators for these three on my home PC, my work laptop, and my iPhone.
I don't program as much as I used to, but I still write programs from time to time. I really like the interchangeable solution type of program for single equations that originated with the HP-65 IIRC. It is usually faster than a SOLVER routine, can handle a higher level of sophistication in the program, and the results can be properly annotated. On the other hand, the programs are much longer.
On my HP-42S I have the following programs:
HW: This is an interchangeable solution to the Hazen-Williams equation for pressure flow in a pipe with an overlapping interchangeable solution to the Continuity Equation. I first wrote this for the HP-41CX back in 1982 when my wife was getting an ultrasound with our first child. I have a similar program for the Mannings Equation for pressure flow, but only an HP-41CX version.
CANAL: This is an interchangeable solution to the Mannings Equation for open channel flow in a triangular, rectangular, or trapezoidal channel. This also started life on the HP-41CX. I use the same subroutine for solving for normal depth and bottom width, with a flag determining which variable to solve for.
SD & SEWER: This is an interchangeable solution to the Mannings Equation for open channel flow in a pipe. This program has two entry points, one for storm drain pipes (uses cfs for the flow rate) and one for sewer pipes (uses gpm for the flow rate). This program includes a solver subroutine for finding the angle from the top of the free surface to the invert of the pipe.
HYDR: This is a multi-menu step-by-step solution for single basin hydrology using the Rational Method. The first step is entering, saving, and/or retrieving coefficients for the rainfall IDF curves for 2-yr, 10-yr, and 100-yr storms. The second step is entering the physical parameters of the basin (drainage length and height, runoff coefficient, area, and roof-to-ground time). The final step is choosing between the Kirpich and FAA equations for time of concentration, then solving for the time of concentration, rainfall intensity, and peak flow. I have ported this to the HP-48G+ and to Excel.
VINT: This program does what I call "vector interpolation." It is used to do linear interpolation between two rows or columns of data from a table based on known index values for the two rows/columns and for the desired interpolated values. It makes extensive use of the HP-42S's matrix capabilities.
NGAS: this program solves for the pressure loss in a natural gas pipe using the isothermal-compressible flow equation.
I also have the following SOLVER routines on my HP-42S:
TVM: Solves the Time Value of Money equation…just like we've always done it.
TB: Solves the equation for sizing thrust and anchor blocks for pressure pipelines.
PM$: Solves a simple project management calculation on project budgets/expenses that I had to do at my previous employer's.
HP: Solves the pump horsepower equation (HP = (Q*H)/(3960*e).
CW: Solves the Colebrook-White equation (i.e. solves the Moody Diagram).
HYT: Solves the equation for sizing hydropneumatic tanks.
FRC: Solves the equation for the frustum of a right cone/pyramid. This is useful for quickly checking the volume of a storm drainage pond.
LOGI: Solves logarithmic interpolation on a graph. Measure the distance between decades on a logarithmic axis using an engineer's scale, then measure the distance from the bottom of the decade to the point in questions, then use this data in the SOLVER routine. I use this mostly to determine coefficients for rainfall IDF curve from their log-log graphs.
TEMP: Converts Celsius to/from Fahrenheit.
FHYD: I can't remember what this is for and my notes are at the office. :-) I'm not recognizing the equation.
FHT: This solves the NFPA (?) equation for fire hydrant flow testing.
I have some less frequently used programs and solver routines that I input temporarily and delete when done due to lack of memory.
I have a feet-inches-fractions calculator that I wrote for the HP-41CX (see the MOHPC program library). Both the promised rewrite and the HP-42S version are about 90% done, but I keep finding more important things to do. I have also ported this to Excel.
So, YES, I still use a programmable calculator.
Edited: 18 June 2013, 1:17 a.m.
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