Datasheet legend
Ab/c: Fractions calculation
AC: Alternating current
BaseN: Number base calculations
Card: Magnetic card storage
Cmem: Continuous memory
Cond: Conditional execution
Const: Scientific constants
Cplx: Complex number arithmetic
DC: Direct current
Eqlib: Equation library
Exp: Exponential/logarithmic functions
Fin: Financial functions
Grph: Graphing capability
Hyp: Hyperbolic functions
Ind: Indirect addressing
Intg: Numerical integration
Jump: Unconditional jump (GOTO)
Lbl: Program labels
LCD: Liquid Crystal Display
LED: Light-Emitting Diode
Li-ion: Lithium-ion rechargeable battery
Lreg: Linear regression (2-variable statistics)
mA: Milliamperes of current
Mtrx: Matrix support
NiCd: Nickel-Cadmium rechargeable battery
NiMH: Nickel-metal-hydrite rechargeable battery
Prnt: Printer
RTC: Real-time clock
Sdev: Standard deviation (1-variable statistics)
Solv: Equation solver
Subr: Subroutine call capability
Symb: Symbolic computing
Tape: Magnetic tape storage
Trig: Trigonometric functions
Units: Unit conversions
VAC: Volts AC
VDC: Volts DC
Years of production:   Display type: 7-segment
New price:  
Display color: Black
    Display technology: LCD
Size: 2½"×6½"×½" Display size: 8 digits
Weight: 3 oz    
    Entry method: Algebraic
Batteries: 3×LR44 Advanced functions: Duct calculations
External power: N/A Memory functions: +
I/O: N/A    
    Programming model: N/A
Precision: 8 digits Program functions: N/A
Memories: N/A
Program display: N/A
Program memory: N/A
Program editing: N/A
Chipset:   Forensic result:  

ductr.jpg (18186 bytes)"Hi there,", says the man on TV, "I want to talk to you about ducts." So begins Terry Gilliam's Orwellian satire, the movie "Brazil". An odd movie it is, but the same can be said about the Carrier Ductronic, one of the oddest calculators I've ever seen.

The primary function of this calculator is to assist the design engineer in sizing air conditioning ducts. For instance, the air velocity, corrected for friction, in a circular duct with a diameter of 12 inches and an overall airflow of 500 cubic feet per minute (cfm) can be calculated using the following keystrokes:

   CLR D 12 Q 500 V =

In response, the calculator displays 636 (feet/minute, duct velocity.)

Printed on the back of the calculator is a table of fitting loss coefficients (i.e., coefficients that describe what happens in a duct at an elbow or junction.)

Pressing the CAL button puts the device into regular calculator mode, where it can serve as a basic four-function calculator with square root. It has a few oddities: for instance, it calculates square roots only to three decimal digits of precision. When entering numbers, if you key in more than 8 digits, the calculator exhibits all kinds of strange, buggy behavior.

Had it not been for the fact that just last year, I was working on a software package for a humidification equipment manufacturer, this device would surely have escaped my attention. I wonder: are there many other similar special-purpose calculating devices out there? In the 1960s and before, slide-rule or circular slide-rule type special purpose calculators (made of wood, plastic, or even more often, cardboard) were quite common. Such electronic calculators, however, appear fairly rare.

Of course, the Ductronic's functionality can easily be replicated on most programmable calculators. Nevertheless, it is an interesting piece that I happily added to my collection of oddball calculators.