sharp el-520w

introduction

Slim and pocket sized with a clip-on, hard protective cover and four way navigator that has become de rigueur of modern calculator shape and design. The el-520w boasts a staggering 419 functions and the latest in sharp’s DAL entry system.

first impressions were very positive for a cheap calculator. It has a large and clear display. One row of dot-matrix for formula and text, and one row below segmented display for the numerical output. Segmented displays are always clearer for numbers. You get ten clear digits plus two small digits for the exponent. Another neat touch are the small 1000's ticks over the number to ease readability of large integers.

The plastic keys are very good and the equals button is wide for convenience. The layout is sensible and colour coded, although I found the placement of clear at the top right accounted for greater finger travel in operation and I would have swapped x² with square root so that square root did not require a 2nd button shift. Otherwise there are some good key optimisations, for example there is no separate ANS key because = performs this duty in most chain calculations. Usefully the +/- key also performs unary minus. This is good because this key is located near the numbers. On some calculators, i've had to hunt though the scientific keys to find unary minus, which is bogus.

This is not a graphical calculator. depending on what you’re looking for, this can be a bonus. Graphing calculators are usually bigger to accommodate the display and therefore heavier and greedier on batteries. Those that aren’t bigger (like the texet gr4f) are just pathetic at graphing. Notably, graphing models are not likely to have a segmented number display being instead a pixel grid and many are difficult to read in low light.

operation & features

Usual for sharp, dating back years, is the non-fussiness with brackets and implied multiplication. I’ve always hated calculators that insist on bracket syntax completion; eg (1+2= becomes a syntax error rather than just giving you 3. phooey!

Its nice to see fractions are still going strong with modern offerings far exceeding historical implementations. Providing the fraction can fit on the screen, there’s no problem. No more 3 digit numerator and 3 digit denominator rubbish. Also, the sharp will have a go at converting a decimal float to a fraction. This it does for values that look highly like their fractional counterpart and it won’t just throw a fraction at you that just happens to approximate the decimal value. For example it wont approximate pi with a fraction. Square root will stay in fraction if possible; eg sqrt(9/16) = ¾.

Impressive is the number base support. For once, there is no dedicated base-n mode, you can simply →hex or →dec a running value. Once in a base, it will remain modal until you switch back to decimal with →dec. number bases seem to be a 10 digit signed representation including binary so there is no way to scroll more than 10 binary bits and also no way to set a “word size” for use with computers. Bases are integer only as usual and nicely the A-F key row does not require “alpha” when using bases.

A welcome addition is the, now standard naming, of P, Q and R functions for normal distribution. These are under the stats menu and are really just variations of the same function. A mere six digit answer is provided which is somewhat lame for a modern machine when, back in 1978, the hp32e would fight it out getting a full 10 digits for its Q function [same as P here] (and its inverse!) whilst performing an entertaining, flickering display dance as it battled the problem.

Complex numbers, although well implemented, were a bit of a disappointment. Firstly complex mode has to be selected, whence the i button can be used in free-form expressions to enter complex numbers. General formula are accepted with input allowing numbers, i , brackets,1/x, x² and x³. Eg iii = -1i and there is a tiny i indicator that is a neat touch. However, this is where the fun stops. I was hoping for square root, cube root and maybe y^x (x integer) but no. nothing more is supported for complex numbers. Feeble, but better than nowt. A far cry from the complex number support of the 1982 hp15c and the 1984 hp71b, the latter handing matrices of complex numbers without the slightest fuss.

On the subject of 21^st century offerings wussing out to 70’s models, isn’t it about time we saw fractional factorial like 2.5! and maybe numbers bigger than 10^100?. Its been standard practice for over 2 decades for hp models to perform these and go to almost 10^500. The sharp el-9900 did manage factorials of n+0.5 so 2.5! was possible but not 2.4

There are fairly good offerings of physical constants and unit conversions. These are both selected by input of numerical index which is impossible to remember. However, the tables of selection are printed on the quick reference card which conveniently fits into a cavity in the plastic cover. The coverage is quite good with welcome addition of UK gallons and UK fluid oz as well as US counterparts. Some of the physical constants are a bit obscure. I would have preferred sharp to have filled up the table instead with astro numbers like the earth mass, tropical years, sidereal day, earth radius etc. as it is all you get in this department is 1 AU.

Advanced features

4 formula memories, definite integration by Simpson's rule, numerical derivatives (not very useful), solving of quadratic and cubic polynomials (including complex roots), 2d linear, power, logarithmic, inverse and quadratic regression, simultaneous equation solving for 2 or 3 unknowns including determinant. newton-rapson numerical solver.

the numerical integration is truely awful. i think its the worst ive ever seen, a special embarrassment for a modern machine, despite the cheap cost.

Conculsion

this unit appears to suffer the same affliction as the casio fx991es! quick repeats of the same digit button often fail to register. this is especially likely for numbers like 100 or 1000 where the zero is pressed quickly.

a jolly good calculator for the money, robust and reliable. if you're looking to buy a cheap calculator, also checkout the casio fx-991es. not sure which is the overall winner. the casio does a few more things, but i like the operation of the sharp and the clear display.