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.