Elsag International N.v.

Donald R Spriggs

Stewart Thoeni

Jeffrey S Mills

Charles J Hess

A method and apparatus for notifying a receiving device of fault conditions in a sensing element or an instrument. The instrument generates an analog signal that has an amplitude which is representative of a variable. The analog signal amplitude has a range defined by a lower limit and an upper limit. The instrument transmits the analog signal to the receiving device. When the instrument detects a fault condition in itself or in the sensing element, the transmitter periodically changes the analog signal amplitude by a predetermined amplitude for as long as the fault condition exists. The predetermined amplitude and its polarity are such that the amplitude of the periodically changed analog signal lies within the range. The receiving device generates an alarm when it detects the pulses.

Method and apparatus for introducing diagnostic pulses into an analog

An electrochemical sensor wherein an ion impermeable plug is interposed between the adjacent faces of the large plugs that are used in the salt bridge. The salt bridge also includes a solid cylindrical plug that passes through the ion impermeable plug to thereby interconnect the adjacent large plugs. The large plugs have a central bore for receiving the glass sense electrode. The impermeable plug has protrusions to provide a better seal between the impermeable plug and the glass sense electrode and the impermeable plug and the housing in which the salt bridge is inserted. In addition, the sensor may also include a rigid liner between the large plugs and the glass sense electrode to act as a barrier to prevent damage to this sense electrode during and after impregnation.

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Reno, NV, United States of America

Donald R Spriggs