Automatic unit converter

Similarly, in particle physics the mass of a particle is often described using energy units such as gigaelectronvolts GeV. As described below, the dimensional analysis system can either perform strict dimensional checking and prohibit force-mass and energy-mass conversion, or it can be made to detect and allow these specific conversions, with strict checking otherwise.

Each of these is a physical constant, expressed in SI units. Dimensional Analysis If the above algorithms are to produce meaningful results, it must be verified that the requested conversion is legitimate; it is clearly impossible, for example, to convert kilograms to meters.

Correctness of unit conversion is verified by the long-established technique of dimensional analysis [bridgman]: the source and goal units must have the same dimensions. Formally, we define a dimension as an 8-vector of integral powers of eight base quantities.

The base quantities are shown in Fig. We have added money , which is not part of the SI system, as a dimension. It can be verified that conversion from one unit to another is legitimate by showing that the dimension vectors of the two units are equal, or equivalently, that their difference is a zero vector. The powers of base quantities that are encountered in practice are usually small: they are seldom outside the range 4. While a dimension can be represented as a vector of eight integer values, with dimension checking done by operations on vectors, this is somewhat expensive computationally.

Since the integers in the vector are small, it might be more efficient to pack them into bit fields within an integer word. In this section, we describe a variation of this packing technique. A dimension vector is encoded within a single bit integer, which we call a dimension integer , using the algorithms presented below. Using this encoding, dimensions can be added, subtracted, or compared using ordinary scalar integer arithmetic. It may be helpful to consider the analogy of doing vector arithmetic by encoding vectors as decimal integers.

We use a similar method to encode a dimension vector as a bit integer. A careful justification of the conditions under which use of the integer encoding is correct is presented following the algorithms. Finally, we argue that these conditions will be satisfied in practice, so that use of the integer encoding for dimension checking is justified.

The vector dimsizes gives the size of the field assigned to each quantity; e. The vector dimvals gives multipliers that can be used to move a vector value to its proper field position; it is defined as follows: The integer dimbias is a value that, when added to a dimension integer, will make it positive and will bias each vector component within its field by half the size of the field.

This algorithm is not needed for unit conversion, but is provided for completeness. The algorithm, shown in Fig. This procedure uses truncated division to extract the biased value from each field of the integer encoding. Dividing by the field size is then used to bring the next field into the low-order position. Our algorithm uses dimension integers, rather than dimension vectors, to check the correctness of requested unit conversions.

Addition, subtraction, and comparison of dimension vectors are simulated by scalar addition, subtraction, and comparison of corresponding dimension integers. These theorems show that checking the dimensions of unit conversions by means of dimension integers is correct so long as the individual dimension quantities are less than half the field sizes given in the dimsizes vector.

We justify the use of the integer encoding of dimension vectors as follows. If a field size of 20 is assigned to length, time, and temperature, and a field size of 10 is assigned to the others, the dimension vector will fit within a bit integer.

The representation allows a power of for each quantity. As long as each element of a dimension vector is within this range, two dimension vectors are equal if and only if their corresponding dimension integers are equal; furthermore, integer addition and subtraction of dimension integers produce results equal to the dimension integers of the vector sum and difference of the corresponding dimension vectors.

This should be quite adequate. We note that dimension vectors are used only in tests of equality: unequal dimensions of source and goal units indicate an incorrect conversion. Two unequal dimension vectors will appear unequal, despite an overflow, unless the incorrect dimension integer corresponds to a very different kind of unit that has a dimension value that happens to be exactly equal; this is most unlikely to happen accidentally. For example, if the user attempts to convert a 20th power of length into a time, the system will fail to detect an error.

This is such an unlikely occurrence that we consider the use of the more efficient integer encoding to be justified. Each unit comprises a multiple-disc clutch for locking gears in direct drive. The front unit has two steel plates or discs splined to the sun-gear drum to form a direct drive unit. It also has three or more composition discs spaced alternatively between the steel discs. These are splined to the planet cage hub and form the driven part of the clutch.

The rear clutch has a similar construction, except that it contains more clutch plates. The steel plates or discs are fastened to the internal gear drum. The steel and composition discs are splined to the intermediate shaft hub. Same as the drum, the clutch discs are circular in shape. When you apply either clutch, an annular piston forces the two sets of clutch discs into contact.

This makes them revolve together as a single locked unit. In the front unit, the application of the clutch locks the sun-gear and the planet cage. However, in the rear unit, the clutch locks the internal gear drum to the intermediate shaft hub.

They lead from the valve controls to the oil delivery sleeve. BorgWarner , Cummins , and ZF are some of the leading manufacturers of automatic transmissions in the world. P — P stands for Parking. With this selection, you can mechanically lock the output shaft of the transmission.

Thus, it restricts the vehicle from moving in any direction. However, the vehicle's non-driven wheels that are still free can rotate. The driven wheels may also rotate individually because of the differential action.

Hence, you should always use the hand brake parking brake as it actually locks the wheels and prevents them from moving. R — R stands for Reverse. This engages the reverse gear of the automatic transmission, permitting the vehicle to be driven backward.

To select reverse in most transmissions, you must come to a complete stop, depress the shift-lock button, and select reverse. N — N stands for Neutral or No gear N. It disengages all gear trains within the transmission. It effectively disconnects the transmission from the driven wheels, allowing the vehicle to coast freely under its own weight and gain momentum. D — D stands for Drive mode. This position allows the automatic transmission to employ the full range of available forward gear ratios.

It allows the vehicle to move forward and accelerate through its range of gears. Some transmissions use this mode to engage the automatic Overdrive. In these transmissions, Drive D locks the automatic overdrive off. This mode locks the automatic transmission in first gear only. In older vehicles, it will not change to any other gear range.

Some vehicles will automatically shift up out of first gear in this mode if a certain RPM range is reached to prevent engine damage. D5 - Cars having five-speed automatic transmissions commonly use this mode for highway use. It uses all five forward gear ratios. D4 - Cars having four or five-speed automatics only use the first four gear ratios. It is mainly used for stop-and-go traffic, such as city driving.

D3 or 3 - Cars with four-speed automatics only use the first three gear ratios. It is used mainly for stop-and-go traffic, such as city driving. D2 and D1 - Older Ford cars used these modes. D1 uses all three gears are, whereas, in D2, the car starts in second gear and upshifts to third. S commonly stands for Sport mode. It operates identically as "D" mode. However, the upshifts change at a much higher engine's rpm. It maximizes the engine output and enhances the performance of the vehicle, mainly during acceleration.

This mode also downshifts at much higher rpm than the "D" mode and maximizes engine braking. However, this mode results in a lower fuel economy. M stands for the Manual mode selection of gears in certain automatic vehicles. The driver can shift up and down at will by toggling the shift lever similar to a semi-automatic transmission. In some models offer a winter mode. It engages the second gear instead of first when pulling away from stationary. It reduces the loss of traction due to wheel spin on snow or ice.

B stands for Brake mode that some models, including electric cars, offer. In non-hybrid cars, B mode selects a lower gear to increase engine braking.

In electric, B mode increases the level of regenerative braking when you release the accelerator pedal. Read on: What are the driving modes? CarBikeTech is a technical blog. Its members have an experience of over 20 years in the automobile field. CarBikeTech regularly publishes specific technical articles on automotive technology.

View all posts by CarBikeTech. About The Automatic Transmission An automatic transmission is a type of transmission or gearbox that can automatically change the gears while the vehicle is in motion.