Capacitive sensing

In electrical engineering, capacitive sensing is a technology, based on capacitive coupling, that can detect and measure anything, conductive or has a dielectric different from air. Many types of sensors use capacitive sensing, including sensors to detect and measure proximity, pressure and displacement, humidity, fluid level, acceleration. Human interface devices based on capacitive sensing, such as trackpads, can replace the computer mouse. Digital audio players, mobile phones, tablet computers use capacitive sensing touchscreens as input devices. Capacitive sensors can replace mechanical buttons. A capacitive touchscreen consists of a capacitive touch sensor along with at least two complementary metal-oxide-semiconductor integrated circuit chips, an application-specific integrated circuit controller and a digital signal processor. Capacitive sensing is used for mobile multi-touch displays, popularized by Apple's iPhone in 2007. Capacitive sensors are constructed from many different media, such as copper, indium tin oxide and printed ink.

Copper capacitive sensors can be implemented on standard FR4 PCBs as well as on flexible material. ITO allows the capacitive sensor to be up to 90% transparent. Size and spacing of the capacitive sensor are both important to the sensor's performance. In addition to the size of the sensor, its spacing relative to the ground plane, the type of ground plane used is important. Since the parasitic capacitance of the sensor is related to the electric field's path to ground, it is important to choose a ground plane that limits the concentration of e-field lines with no conductive object present. Designing a capacitance sensing system requires first picking the type of sensing material. One needs to understand the environment the device will operate in, such as the full operating temperature range, what radio frequencies are present and how the user will interact with the interface. There are two types of capacitive sensing system: mutual capacitance, where the object alters the mutual coupling between row and column electrodes, which are scanned sequentially.

In both cases, the difference of a preceding absolute position from the present absolute position yields the relative motion of the object or finger during that time. The technologies are elaborated in the following section. In this basic technology, only one side of the insulator is coated with conductive material. A small voltage is applied to this layer; when a conductor, such as a human finger, touches the uncoated surface, a capacitor is dynamically formed. Because of the sheet resistance of the surface, each corner is measured to have a different effective capacitance; the sensor's controller can determine the location of the touch indirectly from the change in the capacitance as measured from the four corners of the panel: the larger the change in capacitance, the closer the touch is to that corner. With no moving parts, it is moderately durable, but has low resolution, is prone to false signals from parasitic capacitive coupling, needs calibration during manufacture. Therefore, it is most used in simple applications such as industrial controls and interactive kiosks.

Projected capacitive touch technology is a capacitive technology which allows more accurate and flexible operation, by etching the conductive layer. An X-Y grid is formed either by etching one layer to form a grid pattern of electrodes, or by etching two separate, parallel layers of conductive material with perpendicular lines or tracks to form the grid; the greater resolution of PCT allows operation with no direct contact, such that the conducting layers can be coated with further protective insulating layers, operate under screen protectors, or behind weather and vandal-proof glass. Because the top layer of a PCT is glass, PCT is a more robust solution versus resistive touch technology. Depending on the implementation, an active or passive stylus can be used instead of or in addition to a finger; this is common with point of sale devices. Gloved fingers may not be sensed, depending on the gain settings. Conductive smudges and similar interference on the panel surface can interfere with the performance.

Such conductive smudges come from sticky or sweaty finger tips in high humidity environments. Collected dust, which adheres to the screen because of moisture from fingertips can be a problem. There are two types of PCT: self capacitance, mutual capacitance. Mutual capacitive sensors have a capacitor at each intersection of each column. A 12-by-16 array, for example, would have 192 independent capacitors. A voltage is applied to the columns. Bringing a finger or conductive stylus near the surface of the sensor changes the local electric field which reduces the mutual capacitance; the capacitance change at every individual point on the grid can be measured to determine the touch location by measuring the voltage in the other axis. Mutual capacitance allows multi-touch operation where multiple fingers, palms or styli can be tracked at the same time. Self-capacitance sensors can have the same X-Y grid as mutual capacitance sensors, but the columns and rows operate independently. With self-capacitance, current senses the capacitive load of a finger on each row.

This produces a stronger

2012 Open GDF Suez

The 2012 Open GDF Suez was a women's professional tennis tournament played on indoor hard courts. It was a Premier tournament on the 2012 WTA Tour, it took place at Stade Pierre de Coubertin in Paris, France from February 4 through February 12, 2012. 1 Rankings as of January 30, 2012 The following players received wildcards into the main draw: Alizé Cornet Pauline ParmentierThe following players received entry from the qualifying draw: Gréta Arn Kristina Barrois Mona Barthel Bethanie Mattek-SandsThe following players received entry as Lucky Losers into the singles main draw: Alberta Brianti Jill Craybas Varvara Lepchenko Jelena Janković Kaia Kanepi Sabine Lisicki Jill Craybas Li Na 1 Rankings are as of January 30, 2012 The following pair received wildcard into the doubles main draw: Julie Coin / Pauline Parmentier Monica Niculescu Angelique Kerber def. Marion Bartoli, 7–6, 5–7, 6–3 It was Kerber's 1st career title, she became the first German winner at Paris since Steffi Graf in 1995. Liezel Huber / Lisa Raymond def.

Anna-Lena Grönefeld / Petra Martić, 7–6, 6–1 Official website

4th Mounted Division

The 4th Mounted Division was a short-lived Yeomanry Division of the British Army active during World War I. It was formed on 20 March 1916, converted to 2nd Cyclist Division in July 1916 and broken up on 16 November 1916, it remained in England on Home Defence duties throughout its existence. The 4th Mounted Division was formed on 20 March 1916 from three 2nd Line mounted brigades and the new 2/1st Southern Mounted Brigade; the Headquarters was at Colchester and Brigadier-General Lord Lovat was appointed to command. The brigades were stationed at Wivenhoe, Canterbury and Manningtree. Being formed late, it did not appear to suffer the same organizational problems as other 2nd Line divisions, for example the 1st and 2/2nd Mounted Divisions. In July 1916 there was a major reorganization of 2nd Line yeomanry units in the United Kingdom. All but 12 regiments were converted to cyclists: the rest were dismounted, handed over their horses to the remount depots and were issued with bicycles; the 4th Mounted Division was reorganized as the 2nd Cyclist Division, now commanding the 5th, 6th, 7th and 8th Cyclist Brigades.

On reorganisation, 14th Mounted Brigade – with 2/1st Hertfordshire, 2/1st Queen's Own West Kent and 2/1st Essex Yeomanry – was posted to the new 1st Mounted Division where it formed the new 3rd Mounted Brigade and remained mounted. In exchange, the 10th Mounted Brigade joined as the 8th Cyclist Brigade; the Headquarters remained at Colchester and the brigades at Wivenhoe, Kelvedon and West Malling. It was assigned to the Southern Army, Home Defence Troops, Lord Lovat remained in command; the Headquarters moved to Ipswich in September 1916 and the brigade were now at Wivenhoe, Wingham and Ipswich. A further reorganization in November 1916 saw the 2nd Cyclist Division broken up; the cyclist brigades were dispersed and the yeomanry regiments were amalgamated in pairs to form Yeomanry Cyclist Regiments in new cyclist brigades. The division had remained in England on Home Defence duties throughout its brief existence. List of British divisions in World War I British yeomanry during the First World War Second line yeomanry regiments of the British Army Becke, Major A.

F.. Order of Battle of Divisions Part 2A; the Territorial Force Mounted Divisions and the 1st-Line Territorial Force Divisions. London: His Majesty's Stationery Office. ISBN 1-871167-12-4. James, Brigadier E. A.. British Regiments 1914–18. London: Samson Books Limited. ISBN 0-906304-03-2