Abstract: A magnetic flowmeter transmitter includes a differential amplifier that senses an additive combination of actual flowmeter electrode outputs and simulated electrode outputs. The differential amplifier provides an additive amplifier output. A simulator provides the simulated electrode outputs. The simulator senses the additive amplifier output and provides an error indication when the additive amplifier output is outside a normal range.

Abstract: A magnetic flow meter has a diagnostic circuit that indicates leakage from flowtube electrodes. The diagnostic circuit couples to the electrodes and to ground. The diagnostic circuit samples diagnostic potentials between each electrode and ground, and then generates a sum of the diagnostic potentials between a first and a second electrode that indicates the leakage. The flowtube includes an insulated tube and an electromagnet. A transmitter circuit couples to the electromagnet and electrodes, and then generates a transmitter output representing a flow rate, which can be corrected for the leakage.

Abstract: A magnetic flowmeter with an improved liquid conduction indication has a flowtube assembly with a passage for liquid flow and has an electromagnet mounted outside the passage that provides ramped magnetic excitation. An electrode circuit couples through the passage and generates ramp spikes and a flow signal. A processor receiving the flow signal and generating a flow rate output. The processor also receives the ramp spikes and generates a filtered integral of the ramp spikes as a liquid conduction or empty pipe indication.

Abstract: An AC powered field mounted process control transmitter includes an inrush current limiter which prevents excessive current flow to other circuitry in the transmitter. The transmitter senses a physical parameter, such as flow, and comprises a source of current, a current driven sensing circuitry, the inrush current limiter and measurement electronics for converting the sensed parameter into a transmitter output. The limiter includes a reference voltage source and is in series between the current source and the current driven sensing circuitry. When inactive (i.e. not limiting current), the limiter responds to the series current through itself so that when such current exceeds a predetermined maximum level the limiter becomes active and prevents further current flow. The limiter remains active until the voltage across itself is less than the reference voltage, at which time the limiter becomes inactive.

Abstract: An electromagnetic fluid flowmeter includes empty pipe detection circuitry. The empty pipe detection circuitry applies a common mode asynchronous signal into a pair of electrodes in the flowmeter. Impedance of fluid is determined by measuring the magnitude of the asynchronous signal between an electrode and electrical ground. Impedance is used to determine an empty pipe condition.

Abstract: A sensor which provides an output signal representative of a parameter such as pressure, includes a reflector, a lens and a waveguide which are relatively movable as a function of the parameter. Light from a light source is transmitted by the waveguide toward the reflector. The lens, which is positioned between the waveguide and the reflector directs the light from the waveguide to the reflector and focuses the reflected light proximate a receiving surface of the waveguide. A sensor housing supports the waveguide, lens and reflector so that a relative physical displacement between the waveguide, lens and reflector occurs which is responsive to the parameter. The light received by the waveguide at its receiving surface is a function of the relative physical displacement, and thus a function of the parameter. The waveguide transmits the received light to a light detector which produces an electrical output signal which is a function of the received light and therefore of the parameter.

Abstract: An electrical circuit provides an output signal having a frequency representative of an input signal which has a fundamental frequency responsive to a parameter. The circuit has an amplifier having an adjustable amplitude response with an input coupled to the input signal and an output for providing the output signal as a function of the input signal. A filter is coupled to the amplifier and to the output signal for at least partially determining the amplitude response of the amplifier. The filter has an adjustable rolloff frequency characteristic. An adjustable impedance is coupled to the filter to adjust the amplitude response of the amplifier and adjust the rolloff frequency characteristic of the filter as a function of the input signal. A controller is coupled to the output signal and provides a control signal for adjusting the adjustable impedance and hence the amplitude response of the amplifier and the rolloff frequency characteristic of the filter as a function of the output signal.