CLIUNT FX-991EX Scientific Calculator, Engineering Scientific Calculator With 552 Functions, Lcd Display Scientific Calculators for School Students

Good value for money. Good quality compared to leading brand

TL;DR Summary ReviewThe CLIUNT TY-991EX is a suitable alternative to a similar model made by another more popular brand. On the plus side, it produces very reliable answers to the questions asked of it. On the negative side, it lacks the QR (graph creation) function, it can be quite slow with some calculations, and the buttons have a hard plastic feel to them. Nevertheless, this is an excellent value advanced scientific calculator, and well worth the money.Full Review.The CLIUNT TY-991EX, made by Shenzhen Tianyan Electronics in China, is designed to replicate a similarly-named 991EX calculator from another manufacturer in Japan which I shall refer to in this review by the secret name Cassiopeia to avoid mentioning it in any way.For those buyers already familiar with the Cassiopeia equivalent, it won’t take long to find your way around this model, although there are several differences which make it appear more than a little quirky. Let’s look first, then, at the buttons and their layout.REVIEW SECTION A: BUTTONSCassiopeia – 4 metal buttons in the top row, 4 metal navigation cursor buttons.TY-991eX – 4 metallic plastic buttons in the top row, 4 metallic plastic navigation cursor buttons.Cassiopeia – 22 black buttons with white text, rounded rectangular, rounded convex surfaceTY-991EX – 22 black buttons with white text, octagonal, rounded convex surfaceCassiopeia – 18 white buttons with black text, 2 blue buttons with white text, rounded rectangular, rounded concave surfaceTY-991EX – 18 white buttons with black text, 2 orange buttons with black text, octagonal, rounded concave surfaceWhere To Find It: BUTTON MIGRATIONS AND NEW LABELLING (and “SLOVE”)NB. The Four-Column Table which follows may not render well in all browsers. Please copy the text that follows and adjust formatting if necessary.Cassiopeia Function Button Cassiopeia Position TY-991EX Equivalent New label (If any)Shift Top row, 1st Top row, 3rdMenu – Setup Top row, 3rd Second row, 3rd Function – SetupON Top row, 4th Top row, 1stOPTN – QR Second row, 1st Second row, 4th MISC (no QR function)CALC – SOLVE/= Second row, 2nd Top row, 4th CALC/SLOVE = (all text above metallic button)Integral – Derivative / Colon Second row, 3rd Second row, 1stX – Series Summation Second row, 4th Second row, 2ndSTO – RECALL Fifth row, 1st Fifth row, 3rd SetTo – RELOADENG – Complex Format Fifth row, 2nd Fifth row, 4thLeft Parenthesis – Abs Fifth row, 3rd Fifth row, 1stRight Parenthesis – Comma / X Fifth row, 4th Fifth row, 2ndS<=>D Fifth row, 5th (No movement) CHG7 – CONST 6th row, 1st (No movement) 7 – CONSTANT8 - CONV 6th row, 2nd (No movement) 8 - CONVERSIONREVIEW SECTION B: Physical ConstantsAll the values I have sampled have displayed the same value as their equivalents on the Cassiopeia model. However, care must be taken to round the quoted values to no more than about 4 or 5 significant figures, since the accuracy of the stated values does not generally correspond to their current published values.Some examples follow, with the 2022 CODATA Recommended Values of the Fundamental Physical Constants, National Institute of Standards and Technology, given in square brackets for comparison. As usual, EXP is used as shorthand for “x 10 to the power of”Planck’s constant h = 6.626 069 57 EXP -34 [6.626 070 15 EXP -34]Boltzmann's constant k = 1.380 648 8 EXP -23 [1.380 649 EXP -23]Avogadro’s constant NA = 6.022 141 29 EXP 23 [6.022 140 76 EXP 23]The “Big G” Gravitational constant G = 6.673 84 EXP -11 [6.674 30 EXP -11]Electron charge e = 1.602 176 565 EXP -19 [1.602 176 634 EXP -19]REVIEW SECTION C: Accuracy of Answers1. Mike Sebastian’s "Forensic Formula"INPUT : arc sin( arc cos( arc tan( tan( cos( sin( 9)))))) in degree modeCassiopeia answer = 9.000000007TY-991EX answer = 8.999999998Result: TY-991EX wins2. Powers of rootsINPUT: ( SQRT( SQRT( SQRT( SQRT( SQRT( Pi ))))))^ 32Cassiopeia answer = 3.141592654TY-991EX answer = PiResult: TY-991EX wins3. Inverse Normal calculationINPUT: For X~N(0,1) find x s.t. P(X<x)=0.6Cassiopeia answer = 0.2533471219TY-991EX answer = 0.2533470931Online answer from Desmos = 0.253347103136Result: TY-991EX wins4. Stored value of PiINPUT: Pi – 3.1415926Cassiopeia answer = 5.35898 EXP -8TY-991EX answer = 5.3589793 EXP -8Result: TY-991EX wins5. Large Binomial X~(113, 0.13)INPUT: P(X = 70)Cassiopeia answer = 7.317250193 EXP -34TY-991EX answer = 7.317250236 EXP -34Online answer from Desmos = 7.3172502364 EXP −34Result: TY-991EX winsREVIEW SECTION D: Speed of Calculation – compared with Cassiopeia Models 991EX and 991CWTEST 1 – Non-Converging Newton-RaphsonThe equation x^3 + 1 = 0 has a horizontal tangent at x = 0 so this is the worst possible ‘seed’ for Newton-Raphson. Using SOLVE (or “SLOVE”) with a starting x value of 0, will take a while to solve because the algorithm must first venture slightly left or right of zero in order to find a seed which will lead to convergence.Cassiopeia Model 991CW gives x = -1 in under 1 second.Cassiopeia Model 991EX requires a second ‘Continue’ to reach x = -1TY-991EX reaches x= -1 after about 3 secondsConclusion: TY-991EX is slow, but it gets there.TEST 2 – No SolutionThe equation x^2 + 1 = 0 has no solution. Let’s try to SOLVE / SLOVE this with seed x = 0.Cassiopeia Model 991CW gives "Cannot Solve” in 2 seconds.Cassiopeia Model 991EX gives "Cannot Solve” in 3 seconds.TY-991EX gives "Cannot Solve” in 23 seconds.Conclusion: TY-991EX is VERY slow, but it gets there.TEST 3 – Cycling Solutions (Period 2)The equation x^3 – 2x + 2 = 0 has one real solution around x = -1.8, but the Newton-Raphson process starting at x = 1 cycles between two values (0 and 1).Cassiopeia Model 991CW gives "Continue” in 3 seconds then “Cannot solve” 3 seconds later.Cassiopeia Model 991EX gives "Continue” in 3 seconds then “Cannot solve” 4 seconds later.TY-991EX gives x = -1.769 (etc) in 2 secondsConclusion: TY-991EX is the winner here.TEST 4 – Simultaneous Equations in 4 Unknowns, Real SolutionThis example omits one variable in each equation, so translates to having coefficients simply of 1 and zero. The solutions are integers.x1 + x2 + x3 = 75x1 + x2 + x4 = 80x1 + x3 + x4 = 75x2 + x3 + x4 = 70Cassiopeia Model 991CW solves instantlyCassiopeia Model 991EX solves instantlyTY-991EX solves instantlyConclusion: No noticeable difference in solution speeds.TEST 5 – 4 x 4 Matrix Inversion of an invertible matrix, Matrix A as below:2 0 0 -21 3 1 00 0 -3 01 2 0 0Cassiopeia Model 991CW solves instantlyCassiopeia Model 991EX solves instantlyTY-991EX solves instantlyConclusion: No noticeable difference in solution speeds.TEST 6 – Binomial with very large number of trialsWhile we typically approximate Binomial to Normal once n > 30 and np > 5, it is fun to push calculators to find exact values for large n. For this test, we are going to calculate:P (X < 37) for X~N (144,0.2)Note that individual Binomial probabilities such as P(X = 37) become vanishingly small as n increases (see Accuracy Test above), so we use an inequality, requiring the calculator to find the sum of all these very small values.Cassiopeia Model 991CW solves instantlyCassiopeia Model 991EX solves instantlyTY-991EX solves in under a secondConclusion: No appreciable difference in solution speeds.TEST 7 – Numerical Integration under the Gaussian (Normal) CurveFor unit standard deviation and zero mean, the equation of the Normal curve simplifies to:F(x) = (2 Pi)^(-0.5) e^(-0.5 x^2)We can check the “68, 95, 99.8” rule by finding the area between ±2 standard deviations of the mean, i.e. between –2 and 2.Cassiopeia Model 991CW takes 4 secondsCassiopeia Model 991EX takes 1.5 secondsTY-991EX takes 9 secondsConclusion: The TY-991EX is VERY slow on this one.APPENDIX: DIAGNOSTIC MODE (Courtesy of Guy Macon under Creative Commons Licence)As with the Cassiopeia 991EX, one enters Diagnostic Mode by holding Shift-7 then tapping ON.As with anything else involving the ON key, it doesn't matter what the calculator is doing and it doesn't matter whether the calculator is on or off.You should see:DIAGNOSTICPress ACWhen you see the above, you have 15 seconds to press a key to start the diagnostics. If you are too slow it will go to the normal flashing cursor.The only keys that do anything are ON (ON always works the same no matter what), AC, 8, and 9.AC simply exits the diagnostics and brings up the flashing cursor. 8 and 9 are the actual tests.On the Cassiopeia, there is an additional series of tests under 6, but this is not the case with the TY-991EX, which has only two test modes, under 8 and 9.Test 8 (SHIFT+7, ON, 8):Pressing 8 should display the following:[1] KI1 KO1 [SHIFT] KI8 KO1[5] KI2 KO2 [9] KI3 KO3[)] KI4 KO4 [log] KI6 KO5[logab] KI7 KO6 [0] KI5 KO7"[1] KI1 KO1" means "pressing the 1 key will test the connection between key input #1 and key output #1 on the chip".As you press each key, that line on the display should highlight/change to reverse (light text on a dark background).When it asks you to press the "logab" key it means the x directly below the ALPHA key. This mislabelling may mean that the diagnostic software came originally from a different model.After you highlight the last line, this should instantly result in this display:Battery Model OK!There appears to be no way to test the Solar panel, unlike the Cassiopeia diagnostics.AC should bring you back to the flashing cursor.Test 9 (SHIFT+7, ON, 9):This is the test that is used at the factory to test the calculator after it is manufactured.Many of the tests are the same as the ones above, but this time you have to do all of them to finish.Pressing 9 should display the following:88888888888888888.888888889x10^15This appears to be a test to see if all the segments in an eight-segment display turn on, but this calculator uses a matrix display, so this may be a sign that the same diagnostics are used on many different models.Press SHIFT to enter the Display test.Press SHIFT four more times to enter the Version test.CY-235 VerAPress ACPress AC to enter the key test.The Sequence of Key Presses must be done in this order:Shift, ALPHA, UP, RIGHT, Function, Misc, which takes the count up to 06.I could find no more keys to take this count higher. On the Cassiopeia, each key in turn increments the count.Press ON to exit the testing.

Excellent calculator :) Easy to use with clear buttons :)

Ordered this battery and solar powered scientific FX 991EX calculator to use at work.It has a decent enough 4 line lcd display though could do with it being slightly darker to see the numbers more clearly but the sizes are big enough and I have to use glasses.Function wise it has a large number including basic maths, calculus, statistics, equations.It has a slide on case that I'm glad to see does stay on well as sometimes they can be loose.The buttons are easy to press and the calculator shows which functions where you need to press the shift button.For the amount of functions available it is good value but the instruction manual really needs to be improved as I found it quite complicated.

The CLIUNT FX 991EX Scientific Calculator is a useful tool designed to meet the needs of engineering students and professionals alike. With 552 functions packed into its sleek design, this calculator offers versatility for solving complex equations and tackling advanced mathematical concepts.Featuring an LCD display, the calculator provides clear and easy-to-read results, ensuring accuracy with every calculation. Its solar power capability ensures that you never have to worry about running out of batteries, making it an eco-friendly and reliable option for long study sessions or exams.One of the standout features of the CLIUNT FX 991EX is its comprehensive range of functions, which cover everything from basic arithmetic to advanced calculus, statistics, and engineering applications. Whether you're working on algebraic equations, trigonometric functions, or matrix calculations, this calculator has you covered.In addition to its extensive functionality, the CLIUNT FX 991EX is also designed with convenience in mind. Its compact size makes it easy to carry around in a backpack or briefcase, while its intuitive interface ensures that users can navigate through functions with ease.Overall, the CLIUNT FX 991EX Scientific Calculator is a top choice for school students and professionals in need of a reliable and feature-rich calculator. With its wide range of functions, clear display, and solar power capability, it's a valuable tool for tackling even the most challenging mathematical problems.

Oh my god! Don’t buy this calculator, this calculator is horrible!I had to return the first calculator because many of the buttons did not work immediately after removing the calculator from the box. I returned it and had a new one delivered. The new one turns off randomly and the screen is crooked so that the numbers are cut off on the bottom. I do not recommend this product. It is unreliable and clearly the majority of the calculators produced by this company do not function as intended.Disappointed!

After my son lost his calculator at school this was a perfect replacement for him, he needed a scientific calculator for his maths lesson and this did the job.Being solar powered he will not need to keep changing the battery.Display screen can be seen well when being used and the calculator has a number of different functions also.His teacher commented on how good the calculator is and this made him very happy after accidently losing his old one.Overall I am happy with this.