Personnel-carried dosimeter

An electrochemical sensing cell for use in a dosimeter, comprising:

• a housing including a body having a planar base and upright sides extending therefrom to define an interior region and a lid emplaceable atop said sides to enclose said interior region,
• an opening in said base, and a porous plate of sintered polymer covering said opening, said base having only a relatively narrow peripheral portion, said opening comprising the remainder of said base,
• a generally planar sensing element disposed in said body interior region atop said base, gas being entrant into said cell by diffusion through substantially the entire area of said plate into contact with said sensing electrode,
• a reference electrode and an electrolyte also disposed within said interior region, the electrical current developed across said sensing and reference electrodes in the presence of a certain contaminant in said gas being indicative of the concentration of that contaminant in the gas,
• an annular seal between said peripheral portion and said sensing electrode and surrounding said porous plate, said seal preventing the flow of diffused gas from the region between said porous plate and said sensing electrode to the remainder of the cell interior region,
• a planar, electrically conductive contact situated between a portion of said seal and said sensing electrode,
• a first electrical wire extending through said body and electrically bonded to said planar contact, said sensing electrode pressing against said planar contact in said cell so that electrical current flow from said sensing electrode is via said planar contact and the associated electrical wire, and
• a second electrical wire extending through said body into connection with said reference electrode.

A dosimeter comprising:

• an electrochemical sensing cell and means for enabling the entry of a gas sample into said sensing cell, the current from said cell indicating the concentration of a certain contaminant species in said gas sample,
• a "high level" alarm circuit means, connected to said cell, for providing a first alarm signal when the current from said cell indicates that the present concentration of said certain contaminant species exceeds a first threshold limit value, and
• a "time weighted average" alarm circuit means, also connected to said cell and operative over a certain extended time duration, for providing a second alarm signal when the current from said cell, effectively integrated over a time interval less than or equal to said certain duration, indicates that the time weighted average concentration level of said contaminant species has exceeded a second threshold limit value during that interval, said "time weighted average" alarm circuit means including:
• a frequency converter, cooperatively connected to said cell, for providing an output pulse signal having a frequency proportional to the current from said cell, and
• a counter connected to count the pulses from said frequency converter, said second alarm signal being produced when the count of said counter reaches a preset value within said certain extended time duration.

A dosimeter comprising:

• an electrochemical sensing cell which produces an output signal that is proportional in level to the concentration of a contaminant species in a gas sample, and
• an alarm circuit for producing an alarm signal when the time weighted average concentration level of said contaminant species over a certain extended time duration exceeds a threshold limit value, said alarm circuit including:
• a frequency converter, cooperatively connected to said cell, for providing output pulses having a frequency proportional to the signal level from said sensing cell, and
• a counter connected to count the pulses from said frequency converter, said alarm signal being produced when said counter reaches a preestablished count value within a time interval less than or equal to said certain extended time duration.

A dosimeter comprising:

• an electrochemical sensing cell which produces an output signal having a level that is indicative of the concentration of a contaminant species in a gas sample,
• a frequency converter, cooperatively connected to said cell, for providing output pulses having a frequency proportional to the signal level from said sensing cell,
• counter means, connected when enabled to count output pulses from said frequency converter,
• timing means for enabling counting by said counter means in consecutive time intervals, each of fixed length, during an extended time duration,
• memory means, cooperating with said counter means and said timing means, for storing in separate storage locations the count reached by said counter means in each of said respective consecutive time intervals, the contents of said memory storage locations thereby representing a history of the time weighted average concentration levels of said contaminant species over said consecutive time intervals,
• said electrochemical sensing cell including:
• a housing including a body having a planar base and upright sides extending therefrom to define an interior region and a lid emplaceable atop said sides to enclose said interior region,
• an opening in said base, and a porous plate of sintered polymer covering said opening,
• a generally planar sensing element disposed in said body interior region atop said base, gas being entrant into said cell by diffusion through substantially the entire area of said plate into contact with said sensing electrode, and
• a reference electrode and an electrolyte also disposed within said interior region, said output signal being an electrical current developed across said sensing and reference electrodes in the presence of said contaminant species.

A personnel-carried dosimeter, comprising:

• an electrochemical sensing cell and means for enabling the entry of a gas sample into said sensing cell, the current from said cell indicating the concentration of a certain contaminant species in said sample,
• a frequency converter, cooperatively connected to said cell, for providing output pulses having a frequency proportional to the current from said sensing cell,
• counter means for counting, when enabled, the output pulses from said frequency converter,
• timing means for enabling counting by said counting means during consecutive time intervals each of a fixed duration, and
• memory means, cooperating with said counter means and said timing means, for storing in separate storage locations the count reached by said counter means in each of said respective consecutive time intervals, the contents of said memory storage locations thereby representing a history of the time weighted average concentration levels of said contaminant species over said consecutive time intervals.

A dosimeter comprising:

• an electrochemical sensing cell which produces an output signal having a level that is indicative of the concentration of a contaminant species in a gas sample,
• a frequency converter, cooperatively connected to said cell, for providing output pulses having a frequency proportional to the signal level from said sensing cell,
• counter means, connected when enabled to count output pulses from said frequency converter,
• timing means for enabling counting by said counter means in consecutive time intervals, each of fixed length, during an extended time duration,
• memory means, cooperating with said counter means and said timing means, for storing in separate storage locations the count reached by said counter means in each of said respective consecutive time intervals, the contents of said memory storage locations thereby representing a history of the time weighted average concentration levels of said contaminant species over said consecutive time intervals,
• said electrochemical sensing cell including:
• a housing including a body having a planar base and upright sides extending therefrom to define an interior region and a lid emplaceable atop said sides to enclose said interior region,
• a zigzag recess in said base opening into said interior region, together with a pair of openings through said body at the respective ends of said recess, said openings serving respectively as inlet and outlet ports for the flow of gas through said cell,
• a generally planar sensing element disposed in said body interior region atop said base, gas entrant to the cell through said inlet port flowing through said circuitous recess in contact with said sensing electrode along substantially the entire length of said recess, said gas then exiting through said outlet port, and
• a reference electrode and an electrolyte also disposed within said interior region, said output signal being an electrical current developed across said sensing and reference electrodes in the presence of said certain contaminant species.