A method and apparatus is disclosed, particularly, though by no means exclusively, useful in touch--screen computer CRT display systems and the like, and more generally in other force and/or torque measurement systems, as in weighing and the like, in which (1) lineal and/or rotational acceleration of the system is sensed in response to inertial interference effects such as tilt or movement that introduce errors into the force and/or torque measurements, and/or (2) inertial error correction from the force data itself is obtained, such as derivative order corrections; and such data is used to correct the force and/or torque measurements. A novel calibration technique for deriving appropriately descriptive coefficients to the particular system for the correcting data, is also disclosed.

A touch screen digitizing system includes a touch screen unit including a first resistive sheet with opposed x+ and x- terminals and a second resistive sheet with opposed y+ and y- terminals, and an ADC having first and second reference input terminals. A first switch is coupled between a first reference voltage and the x- terminal, and a second switch is coupled between the x+ terminal and a second reference voltage for energizing the first resistive sheet. A third switch is coupled between the first reference voltage and the y- terminal, and a fourth switch is coupled between the y+ terminal and the second reference voltage for energizing the second resistive sheet. Switching circuitry couples an input of the ADC to the y+ terminal while the first resistive sheet is energized and the second resistive sheet is not energized, and also couples the input to the x+ terminal while the second resistive sheet is energized and the first resistive sheet is not energized. The structure provides continuous calibration of the full-scale analog touch screen output of the full-scale digital output of the ADC irrespective of sharply different variations in resistances of the switches and resistive sheets.

A data channel monitor is provided for a data channel that converts analog signal data to binary digital bits. The monitor allows the quality of the data detected to be measured in conjunction with predetermined processing steps performed in the data channel. The channel monitor obtains channel data and uses the data to determine detection margins, which are a measure of the data quality. The detection margins are compared with an acceptable value(s). Error references are generated if a detection margin is outside an acceptable range. The data monitor also preferably includes a diagnostic capability wherein all detection margins may be stored for off-line analysis whenever the data channel is placed in diagnostic mode.

A safety device in a motor vehicle includes a sensor which provides an output relating to a physical quantity such as acceleration. The signal is passed to a subtracting circuit and the output of the subtracting circuit is fed to a further circuit arrangement which derives a signal value corresponding to an off-set component present in the signal, this signal value being subtracted from the original signal to provide an output which relates solely to the component of the original signal corresponding to the measured physical quantity. The output of the subtracting circuit is used to initiate the operation of the safety device such as an air-bag or seat belt pre-tensioner.

A combination keyboard and pointing device is incorporated in a portable computer and includes a dielectric base member on a top side of which a spaced series of electrically conductive pad member portions of a capacitance-based proximity sensing system are formed. Manually depressible key members are positioned above the pads. With the sensing system switched to a typing mode, the pads capacitively sense the proximity, velocity and acceleration of a user's fingers depressing their associated keys and output signals useable by the computer to display the character associated with the depressed key. A sensed increased stroke velocity of each manually depressed key may be used to alter the key character image displayed on the screen, for example capitalizing, bolding or underlining the character. The sensing system may be manually or automatically switched from its typing mode to a pointing mode in which it capacitively senses various hand and finger motions and orientations to carry out various pointing functions, such as cursor movements, pick functions, and scrolling functions, in response to the sensed hand and finger motions and orientations.