Texas Instruments TI-30 ECO RS (2009)

Date of introduction:  January 2009 Display technology:  LCD
New price:   Display size:  10 + 2
Size:  5.9" x 3.0" x 0.50"
 150 x 75 x 13 mm3
Weight:  2.9 ounces, 82 grams Serial No:  
Batteries:  n.a. Date of manufacture:  mth 04 year 2010 (K)
AC-Adapter:   Origin of manufacture:  China (N)
Precision:  12 Integrated circuits:  
Memories:  3    
Program steps:   Courtesy of:  Joerg Woerner 

Texas Instruments released rather silent in January 2009 this TI-30XA with larger digits and even in September 2009 most stores in Upstate New York carry a mix of "old" and "new" calculators in their shelves. The only visible difference for the customer is a small sticker "New Larger Digits!" on the sales box. On a business trip to Germany in 2010 we found the related TI-30 ECO RS with the larger digits, too.

A first inspection of the revised TI-30 ECO RS confirms indeed a nice display with bold, huge digits and even without placing two calculators side-by-side we recognized the improvement immediately.

Disassembling this TI-30 ECO RS manufactured in April 2010 by Nam Tai Electronics, Inc. in China reveals no surprises. The printed circuit board (PCB) of the calculators looks very familiar to us and even the product name etched on it confirms: TI-30XA SLR.

Since its introduction in 1996 we verify with each TI-30Xa based calculator the presence of the Logarithm Bug and - yes....

The algorithm problem known as "Logarithm Bug" was implemented already 1991 with the TI-35X and TI-36X SOLAR and floats around in various calculators.
The best way to demonstrate the logarithm bug could be found with the exponential function, one of the most important functions in mathematics. It is written as ex and can be defined as a limit of a sequence:

The calculation of this expression will yield to unexpected results due to:

The ln(1 + x) problem 
The way yx is calculated

Using n=109 should reveal a very close approximation of ex=2.71828183 (rounded to 9 digits) but this TI-30 ECO RS manufactured in 2010 still indicates 2.71919279.

horizontal rule

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Joerg Woerner, January 19, 2011. No reprints without written permission.