Retro Review: Texas Instruments TI SR-51-II
Quick Facts
Model: SR-51-II
Company: Texas Instruments
Years: 1976
Type: Scientific
Batteries: 1 × BP6, with AC-Adapter**
Operating Modes: AOS
Number of Registers: 3
Display: 10 digit - red seven segment digits
Leather Case
** I purchased the calculator on eBay not to long ago from night_owl_items, who made it so the SR-51 II can run on two AA batteries, making it one of the kind and extend it's life.
Features
* Trigonometric functions and inverses
* Hyperbolic functions and inverses
* Logarithms and exponentials
* Factorials of positive integers
* Percent and percent change
* Arithmetic, powers, and roots
Conversions
There are eight conversions:
* in · mm
* gal · l
* lb · kg
* °F · °C
* D · R (degrees - radians)
* G · R (grads - radians)
* DMS · DD (degrees-minutes-seconds - decimal degrees)
* P → R (polar - rectangular conversions)
The [ 2nd ] key sequence converts left to right
The [ 2nd ] [ INV ] key sequence converts right to left
Angle Modes
The SR-51-II has the three customary angle modes: degrees, radians, and grads. Unfortunately there is no angle mode indicator. The way to:
Degrees Mode: 0.5 sin^-1 returns 30
Radians Mode: 0.5 sin^-1 returns .5235987756
Grads Mode: 0.5 sin^-1 returns 33.33333333
Storage and Storage Registers
The SR-51-II has three memory registers. The calculator also has storage arithmetic:
SUM: STO+
INV SUM: STO-
PROD: STO×
INV PROD: STO÷
The CONST Function
The CONST is an access to common scientific functions, but allows the user to do a short arithmetic calculation, includes roots, powers, and percent change.
Example: Subtract 100 from 290, 370, and 480 respectively.
100 [ - ] [ 2nd ] (CONST)
290 [ = ] returns 190
370 [ = ] returns 270
480 [ = ] returns 380
Example 2: Multiply 172, 288, and 382 by 6 respectively.
6 [ × ] [ 2nd ] (CONST)
172 [ = ] returns 1032
288 [ = ] returns 1728
382 [ = ] returns 2292
Statistics
The statistics modes have one and two variable statistics. What is unique of the SR-51-II is that the y-variable is primary. However, entering two variable statistics remain the usual: x [ x<>y ] y [ Σ+ ].
[ 2nd ] (MEAN): mean of y data; [ INV ] [ 2nd ] (MEAN): mean of x data
[ 2nd ] (S.DEV): standard deviation of y data;
[ INV ] [ 2nd ] (S.DEV): standard deviation of x data
[ 2nd ] (VAR): population variance of y data;
[ INV ] [ 2nd ] (VAR): population variance of x data
Solid calculator. I wish the SR-51-II had a random number function and angle mode indicator.
Source:
Woerner, Joerg. "Texas Instruments SR-51-II" Datamath. December 5, 2001. Last Retrieved November 1, 2022. http://www.datamath.org/Sci/MAJESTIC/sr-51-II.htm
Eddie
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