Abstract: A modular input/output (I/O) system for field wiring includes a plurality of base units into which electronics modules providing appropriate signal processing are plugged. A backplane in each base unit provides leads between the electronics module and associated terminals to which the field wiring is connected and also hosts a communications bus through which the electronics modules on serially connected base members communicate with a controller. Switching modules plugged into some of the base members selectively switch field signals applied to terminals for an associated electronics module to another electronics module for redundancy, or switch test signals into the associated electronics module in place of the field wiring signals. The test signals are generated by yet another of the electronics modules while still another electronics module generates control signals for the switching modules.

Abstract: A system for automatically calibrating a semiconductor wafer handling robot so that the robot will move wafers into and out of precise locations within enclosures that form process stations or storage cassettes is disclosed. The system comprises a controller having memory and logic sections connected to a robot having an articulated arm that is movable in vertical (Z), horizontal (.theta.), and radial (R) directions and having a wafer retaining wand at the end of the arm. Dimensional characteristics of the robot wand and the enclosures are stored in the controller memory. Sensors are provided at each enclosure and/or the robot wand which are activated and provide signals to the controller that are relative to the wand position. The robot is programmed to execute a series of progressive movements at each enclosure location which are controlled by a combination of sensor response signals and the appropriate dimensional characteristics.

Abstract: A distributed process control system drop for controlling the operation of an industrial process includes a first workstation or personal computer running industrial continuous process control software on an open architecture operating system and operable to analyze input information provided from the industrial process according to a predetermined set of rules and generate output information provided to the industrial process to control the operation thereof. A second workstation or personal computer connected with the first workstation via a non vendor-specific, international standards-based data highway normally runs in a backup mode and also runs the industrial process control software on an open architecture operating system to perform the same analysis as the first workstation and generate backup output information.

Abstract: A modular input/output (I/O) unit utilizes plug-in personality modules to provide any one of a variety of interfaces between I/O signal processing cards mounted in plug-in electronics module and a bank of terminals providing connections for field wiring.

Abstract: Method and apparatus for measuring the velocity, whether rotary or reciprocating, of a servo shaft driven cyclically by a motor, without employing a tachmometer, while maintaining accuracy despite environmental electrical noise. From movement of the shaft a pair of overlapping square-wave signals in quadrature are produced with transition expressible in Gray Code for each cycle. A clock continuously produces a large number of evenly spaced clock pulses constituting a series of consecutive sample intervals. A signed value representing the algebraic sum of all the quadrature transitions occurring during a sample interval is determined and stored. The number of clock pulses between two quadrature transitions, each transition being the last qualified transition of the two most recent sample intervals having transitions is determined. A computer divides the sample intervals by the number of clock pulses which occurred between the selected quadrature transitions.

Abstract: Method and apparatus for measuring the velocity, whether rotary or reciprocating, of a servo shaft driven by a motor, without employing a tachometer. From the movement of the shaft is produced a pair of signals in quadrature, with transitions expressible in Gray code for one cycle as 00, 01, 11, 10 and then back to 00. Meanwhile, a clock provides a large number of evenly spaced counts per selected quadrature transitions. The number of counts between two selected quadrature transitions is read and the total number of quadrature transitions between the selected transitions is divided by the total number of counts during the same time.

Abstract: A system for measuring moisture content in a porous material uses a microprocessor. The sample of material is placed on a load cell which provides an output to an analog-to-digital converter. The analog-to-digital converter provides a digital input for the microprocessor. The microprocessor is capable of providing an output indicative of the moisture content as a wet basis or a dry basis output. The system provides a highly accurate measurement of the moisture content while minimizing operator errors.