Abstract: A beam splitter for transmitting and deflecting light comprises a foil having a top surface and at least one hole therethrough. A highly reflective finish is provided on the top surface of the foil. Light is transmitted through the holes in the foil while other light is reflected from the reflective finish on the top surface.

Abstract: A sigma-delta technique is used to generate a digital representation of the incoming analog signal amplitude. The integration stage of the converter holds an analog error term relative to the ratio of an incoming analog input signal to a reference voltage. The incoming analog signal is disconnected at the end of the conversion. The error term is monitored through a comparator as charge packets are applied to the input of the integration stage. The number of charge packets needed to have the error term cross zero provides information which can be used to extend the resolution of the analog to digital converter.

Abstract: A process and apparatus for shadowing memory uses a single memory chip which is addressable into an address field which is smaller than the memory chip. A program having a main control portion is programmed into a main memory area of the memory chip and is directly connected to a main address space of the address field. The program also includes a plurality of secondary program portions which can be used one at a time with the main control portion of the program. Each of the secondary program portions is stored in a separate secondary and shadowed memory area of the memory chip. A secondary address space of the address field which is large enough to accommodate only one secondary memory area at a time, is controlled so as to be latched to only one secondary memory area at a time. Latching is achieved through higher bits of address locations in a selected portion of the address field.

Abstract: A peak amplitude detector for use in a synchronized position demodulator associated with a linear variable differential transformer. The peak amplitude detector adjusts for phase shift in the transformer and maintains the full bandwidth of the transformer. The detector obtains the maximum positive or negative amplitude of the sinusoidal signal at one of the secondary windings of the transformer by first counting either a positive or negative half cycle of the signal and then while down counting one half of the counted half cycle sampling the amplitude of the sinusoidal signal. The sampling ends when the count reaches zero.

Abstract: A method for compensating for the differences in temperature across a cell used to sense pressure. A microprocessor calculates a dynamic temperature factor signal by multiplying a signal representative of temperature change across the cell by a coefficient based on measurements made of the effect of temperature change on the cell. The dynamic temperature factor signal is then subtracted from the signal representative of the differential pressure sensed by the cell to thereby provide the dynamic temperature compensation.

Abstract: A method for filtering digital signals in a pressure transmitter. The transmitter includes a microprocessor. In each operating cycle of the microprocessor included in the transmitter, the method determines if there are any noise spikes in the signal at the input to the microprocessor representative of pressure and provides rejection for such spikes. The method also provides for a faster response to a step change in pressure than is provided by conventional filtering methods and also dampens small fluctuations in the filtered output signal.

Abstract: A magnetic actuator for adjusting the zero and span settings of a transmitter used in industrial process control systems. The actuator has a single magnet in a housing. The actuator is removable from the transmitter.When the actuator is unactuated the magnet is in a null position wherein it does not actuate either the zero or span setting reed switches. The magnet can be moved to either a first position wherein it actuates the zero setting reed switch or a second position wherein it actuates the span setting reed switch. The actuator applies a torque in the proper direction to return the magnet to the null position when the torque applied to move the magnet to either the first or second position is removed.

Abstract: A cover lock assembly for a process transmitter having threadably removable end caps and corrugated outer surfaces is provided for engaging the corrugated surfaces by way of a toothed cover lock which is removably affixed to the transmitter housing.

Abstract: An electrochemical sensor wherein the salt bridge is a unitary plug of semipermeable material which is saturated with an electrolyte. The plug has a spiral cut from its outer surface to the central bore of the plug. The spiral has at least one complete turn and starts at or near one end of the plug and stops at or near the other end of the plug. A layer of impermeable material is deposited in the plug to thereby form an ion impermeable spiral barrier.

Abstract: A device which is a combination of a method and apparatus and a filter, such as but not limited to, a conventional lag filter for digitally processing and filtering signals used in industrial control applications. The method and apparatus provides a factor which is used by the filter to process the digital signal at the input to the device. The method determines if the change in the input signal is either due to noise or a valid signal change. Information which gives a past analysis of the trend in direction of the signal at the input to the device is used in the method. The trend information includes a factor representative of the past history of the trend. The method uses the most recent trend indicator to determine to a reasonable degree of confidence if the signal currently at the input to the device is or is not characteristic of noise. If the signal at the input is not believed to be characteristic of noise, then the method adjusts the trend indicator by a tracking credit.

Abstract: The characteristics of the field process system controlled by a self tuning controller are obtained by analyzing the open loop response of the process variable to a step applied at the controller's control output. A first-order system response with pure time delay is used to approximate a higher-order field process system's actual response. The overall deadtime and time constant of the first-order approximation are determined. The maximum slope of the process variable response to the step is stored along with an assigned time of its occurrence and an assigned process variable. The stored information is used to approximate the overall deadtime. In one embodiment the stored information is assumed to be the data obtained from a second-order response having a 10:1 time constant ratio and is used to find the assumed second-order time constants which are used to find the first-order time constant.

Abstract: The firing rate and the feedwater flow rate of a universal pressure boiler are controlled using a cascaded steam temperature control system. The secondary superheater outlet temperature comprises an outer loop for the control system, while the convection pass outlet temperature comprises an inner loop for the control system. Control variables for the system include the secondary superheater outlet temperature, the convection pass outlet temperature and the difference between the primary superheater outlet temperature and the secondary superheater inlet temperature.

Abstract: An electronic ringing generator circuit with provision for power efficient current limiting and preservation of sinusoidal or near sinusoidal output waveform under overload conditions. A pulsewidth modulated DC-DC power convertor produces supply voltages for a linear class B power amplifier which has a low frequency low level sinusoidal signal applied to its input through a first controllable attenuator. The DC-DC convertor's reference input is also driven through a second controllable attenuator which is coordinated with the first controllable attenuator. The attenuators are operated in such a way that if the amplifier's output current exceeds a predetermined value, both the input signal and amplifier supply voltages are reduced in a coordinated manner so that simultaneously the output AC waveshape is preserved and the amplifier continues to operate at or very near optimum efficiency. The amplifier may be operated to produce a sinusoidal output (crest factor =1.

Abstract: A pneumatic servo comprises a motor having a shaft for rotation in response to an electrical signal. A cam is connected to the shaft for rotation therewith. The cam has an outer profiled periphery and opposite sides. A pneumatic nozzle having an opening for directing a flow of gas toward one side of the cam near the periphery, obscures the flow by different amounts as the cam rotates to create a back pressure in the nozzle comprising a pneumatic signal. A curved projection engages an opposite side of the cam, the projection being aligned with the nozzle opening and reducing oscillation excursions of the servo at gas pressures in the nozzle of above 12 psi.

Abstract: A clock synchronization scheme for synchronizing a remote terminal to a distantly located central office terminal. In order to obtain synchronization, the central office terminal repetitively transmits a frame which has in it only one synchronization bit located in a predetermined position. The remote terminal includes a voltage connected oscillator whose output is used to determine when the predetermined bit position should be received from the central office terminal. The remote terminal controls the frequency of the oscillator based on the phase and frequency difference between the actual received synchronization bit and the bit position that the terminal says that bit should be received in. Once synchronization is achieved, the central office terminal transmits in each frame a three bit window which includes the synchronization bit. The remote terminal then searches each frame for the three bit window as long as synchronization is maintained.