Abstract: A coding system for various I/O module elements of an I/O cabinet assembly is disclosed which is able to identify analog, digital and control I/O modules by appropriate functional representation combined with a distinct color code found on the front of each module and to identify appropriate internal field wiring connections in the identified module by the module identifying color. Each module has a written identification such as A—for analog, D—for digital and C—for control, I—for input, O—for output combined with an appropriate color bar identifying the type of module. Thus process and terminal blocks forming and I/O unit are easily matched for assembly and are easily inserted into an I/O cabinet in the proper location.

Abstract: A system for loading upgraded, that is, new boot code and/or main firm ware has a programmable memory that has two boot code regions. One of the regions holds the active boot code while the other region holds the inactive boot code. During a boot code upgrade, the boot code in the inactive region, is under control of the boot code in the active region, replaced with the new boot code. Once the replacement process is verified as having been successful and the vector table in the new boot code is copied to the processor vector table in the memory, the processor can be reset so that the new boot code becomes the active boot code and the previously active boot code becomes the inactive boot code.

Abstract: A unique cabinet mounted I/O assembly adapted for integration into a control system which allows a block I/O assembly to be mounted in both sides of the cabinet allowing a blind fit of power and signal connections insuring that power will be provided to the block I/O assembly before any application of signals thereto and preventing any mismatching of I/O units to wrong processor blocks in the cabinet by a color matching scheme.

Abstract: A unique electrical connector for power and signal connections from an I/O cabinet of a control system to a block I/O assembly mounted in the cabinet to allow a blind fit of power and signal connection of power and signal connections insuring that power will be provided to the block I/O assembly before any application of signals thereto.

Abstract: A FSK demodulator which uses the combination of a digital phase comparator and a digital controlled oscillator (DCO) in the form of a state machine to demodulate an FSK signal. The phase comparator compares the phase of the FSK signal with the output of the DCO to provide a signal to the DCO having a level dependent on the phase relationship between the two signals at the input to the comparator. The demodulator also includes a filter to obtain the data from the signal at the output of the comparator.

Abstract: A radio frequency isolation system for geographically distance signal sources comprising AC and DC signals which develop differences in ground potential includes a control cabinetry chassis with the DC input signal source being electrically grounded to the chassis at the input side of the cabinetry and a hybrid circuit connected to the chassis through capacitors with the AC input signal being connected to the hybrid circuit for grounding the signal at both the input and output ends of the hybrid circuit to the chassis.

Abstract: A unique cabinet mounted I/O assembly adapted for integration into a control system which allows a block I/O assembly to be mounted in both sides of the cabinet allowing a blind fit of power and signal connections insuring that power will be provided to the block I/O assembly before any application of signals thereto. and preventing any mismatching of I/O units to wrong processor blocks in the cabinet by a color matching scheme.

Abstract: The present invention is drawn to an I/O block (38) assembly comprises a plurality of specifically configured I/O blocks (38) mounted to a conductive column (46) providing power to and communication between the I/O blocks (38) with each individual I/O block (38) programed for a specific function requiring that the proper I/O module (42) must always be inserted into the right base (40). This is accomplished by providing a set of pegs or pins (50) individually configured on the base (40) which match a complimentary series of openings 74 on the I/O module (42) formed by a mask (70) covering a plurality of holes (60) while leaving the holes matching the pins (50) uncovered.

Abstract: A signal isolating device for an input digital signal has a first photo-coupler which is activated by the differential pulse produced at the leading edge of the digital signal and a second photo-coupler which is activated by the differential pulse produced at the trailing edge of the digital signal. A positive feedback system is connected in push-pull fashion with the photo-couplers for producing an output digital signal that corresponds to the input digital signal. The positive feedback system may be implemented by a buffer that includes a resistor for keeping the buffer in a stable state even when both of the photo-couplers are non-conductive.

Abstract: Anti-windup and noise protection that can be used with any general digital controller. The anti-windup technique allows the implementation of noise filtering techniques to decrease or eliminate chatter of the control output at the limit. In a higher order controller that uses a feedforward signal, the anti-windup technique prevents an unexpected change in the control output when a step change occurs in the feedforward signal. The technique can be used to provide anti-windup protection in both single layer and multi-layer control schemes.

Abstract: A control station for use individually or as an element of a distributed process control system has an improved high frequency isolation and grounding system incorporating a "Chomeric" conductive foil tape on both the cabinet front and back walls as well as on the doors and a V-shaped "Chomeric" conductive gasket placed between the cabinet wall and the door in the area of the conductive tape to insure proper sealing of the door and opening to eliminate all RFI (radio frequency interference) problems and meet European standards for RFI cabinet emmisions. This cabinet also has a grounding system comprising a large area swing clip for removing the door as well as a hybrid grounding circuit to eliminate ground potential differences due to geological variations found in different parts of the landscape since the signals reaching the cabinet may originate at remote locations up to a mile or more from the cabinet.

Abstract: A ground loop detector circuit and method for an instrument that is used with either a pH sensor or a conductivity sensor. In the instrument used with a pH sensor, an AC diagnostic signal is provided to the sensor. A high input impedance diagnostic signal monitor monitors the voltage at a node adjacent the output of the diagnostic signal source. The occurrence of a ground loop causes the voltage at the node to drop. The instrument used with the conductivity sensor, not only monitors current returning to the diagnostic circuitry from the sensor but also uses a high input impedance monitor to monitor the current leaving the diagnostic circuit to the sensor. The relationship between the current from the sensor and the current to the sensor can be used to determine if a ground loop has occurred as such a loop will cause the current from the sensor to be less than the current to the sensor.

Abstract: A custom segment that includes softkey prompts which are included as icons in the display. A number of keys are associated with the display. Several functions are assigned to the same key. The prompts that must be displayed for each function so that the operator or user of the device in which the display is used could easily operate the keys to obtain those functions were identified at the start of the device design effort. The prompts were assigned to the keys in a logical manner so that in each state of each operating mode of the device an easy to understand set of prompts appear on the display.

Abstract: A digital implementation for a carrier detector. The detector determines if the carrier frequency at any instant is within a predetermined frequency band. The detector further determines if the detected frequency remains within the predetermined frequency band for a predetermined period of time. The detector also provides an indication that there has not been any loss of carrier for another predetermined period of time.

Abstract: An electromagnetic flowmeter comprising a non-conductive body having a central channel, first and second diametrically opposed cavities extending from the channel, and third and fourth cavities positioned, relative to liquid flow through the central channel, upstream and downstream of the first and second cavities, respectively. First and second self-sealing measuring electrodes are respectively positioned in the first and second cavities, and third and fourth self-sealing grounding electrodes are respectively positioned in the third and fourth cavities. Each of the electrodes has a tip and a multiplicity of saw-tooth edges extending outwardly from the periphery of the electrode. Each of the saw-tooth edges has a crest, a face normal to a longitudinal axis of the electrode and extending from the crest to the periphery, and a face at an acute angle to the longitudinal axis of the electrode and extending from the crest to the periphery closer to the tip than where the normal face reaches the periphery.

Abstract: A distributed control system wherein status is propagated through the system along with the signal with which the status is associated. The function blocks of the system include rules for propagation of the status through the system. The system may also include function blocks for testing the propagated status to determine if the same is bad and function blocks to force the propagated status to have a certain status. The rules may be customized by the user, for example, to block status propagation through a function block.

Abstract: A method of manufacturing an electromagnetic flowmeter and an electromagnetic flowmeter wherein the measuring electrodes do not protrude into the flow channel and instead form part of the flow channel wall. The method for manufacturing the flowmeter includes the steps of forming the flowmeter body with a central channel smaller than that which is desired for final flowmeter use, inserting into the body electrodes with tapered tips which extend into the central channel, and reaming the central channel whereby the central channel is enlarged to its final diameter and the electrode tips are cut. The cut tips form concave cross sectional areas which are continuous and flush with the central channel wall. The resultant flowmeter has measuring electrodes which do not protrude into the channel. This substantially reduces turbulent flow of the measured liquid as it passes through the measuring region of the flowmeter, and a more accurate reading results.