Texas Instruments TI-30Xa (2015)

Date of introduction:  July 2015 Display technology:  LCD
New price:  $10.99 (SRP 2016) Display size:  10 + 2
Size:  6.0" x 3.0" x 0.6"
 153 x 76 x 15 mm³
Weight:  2.5 ounces, 72 grams Serial No:  
Batteries:  LR44 Date of manufacture:  mth 05 year 2015 (M)
AC-Adapter:   Origin of manufacture:  Philippines (L)
Precision:  14 Integrated circuits:  
Memories:  3    
Program steps:   Courtesy of:  Joerg Woerner 

End of March in 2016 we received a strange email from fellow calculator collector Akira Morita in Japan: "I bought a TI-30Xa and TI-30 ECO RS on Amazon - the (Logarithm) Bug is fixed". To be honest, we couldn't believe that Texas Instruments finally fixed this quirk floating with the TI-30Xa since its introduction in 1996 and decided to purchase both calculators.

And yes, the TI-30Xa and TI-30 ECO RS are bug free!

Disassembling this TI-30Xa manufactured in May 2015 by Kinpo Electronics, Inc. in the Philippines reveals a small surprise. The printed circuit board (PCB) of the calculators sports now a prominent SR-32 logo - with a revision index of 10-2. A TI-30XA calculator manufactured four years earlier by Kinpo Electronics, Inc. carried a SR-30-12 designator.

Since its introduction in 1996 we verify with each TI-30Xa 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) and this TI-30XA manufactured in 2015 indeed indicates 2.718281827.

Running Mike Sebastian's Calculator forensics reveals with 9.0000000304418 even an improved 14-digits precision on the internal calculations compared with the previous 12-digits design.

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© Joerg Woerner, May 17, 2016. No reprints without written permission.