Measuring instrument

Details Measuring instrument Measuring instrument

1996-11-15

1998-10-13

Tung, T.

Chemistry: electrical and wave energy

Apparatus

Electrolytic

204424, 204427, 2057845, G01N 27407

Patent

active

058207392

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a measuring instrument, particularly an electrochemical measuring sensor, of the type having a sensor element arranged at a measuring point, which sensor element can be connected via electrical connecting leads with an evaluating circuit removed from the measuring point, and with the electrical connecting leads being guided so as to be protected against external influences, especially against high temperature influences, at least in the proximate of the measuring point.


PRIOR ART

Measuring instruments of the generic type mentioned above are known. Electrochemical measuring sensors, for example, designed in a so-called finger construction, are used in motor vehicles to determine the oxygen content in exhaust gases of internal combustion engines. These measuring instruments have a sensor element which is arranged directly at a measuring point and which is fixed so as to be sealed in a metallic housing.
As is known, the sensor element has a solid-state electrolyte which is arranged between two electrodes. Depending on the outfitting of the sensor element, an additional heating device is provided. In order to evaluate the sensor signals determined with the sensor element or to supply the sensor element with the necessary heating voltage, electrical connecting leads are provided which connect the sensor element with a corresponding circuit arrangement.
Since the sensor elements, for example, during measuring of the oxygen content in exhaust gases, are arranged in a region which is exposed to a relatively high temperature, it is known to guide the electrical connecting leads so that they are protected at least in the proximity of the measuring instrument. For this purpose, it is known to guide the electrical connecting leads in a metal tube which ends at a specific distance from the measuring point. For realizing the connection of the sensor element with the evaluating circuit, lines insulated with plastic material, usually PTFE-insulated, are fixed to the end of the lines that are guided in the metal tube. At their other end, the lines insulated with plastic material are provided with a plug device which can be connected to a counterplug device disposed on the cable harness.
As is known, the connection between the lines insulated with plastic material and the lines disposed in the metal tube is implemented as a nondetachable welded, crimped and/or soldered connection. To ensure the operating safety of this connection point, it is known to coat it with plastic material and to additionally seal the lines insulated with plastic material with rubber bushes. The drawback of this solution is that the cable harness of the electrical connecting leads, which harness is connected to the measuring instrument, is relatively long, for example, up to two meters, so that a relatively complex installation in the motor vehicle is required.


SUMMARY AND ADVANTAGES OF THE INVENTION

The above mentioned problems according to the prior art generally are overcome according to the present invention by a measuring instrument, particularly an electrochemical measuring sensor, having a sensor element arranged at a measuring point, which sensor element can be connected via electrical connecting leads with an evaluating circuit removed from the measuring point, with the electrical connecting leads being guided so as to be protected against external influences, especially against high temperature influences, at least in the proximity of the measuring point, and wherein at its end facing away from the sensor element, a protective device receiving the electrical connecting leads is provided with a connecting device which can be connected to a connecting lead to the evaluating circuit.
In contrast, to the known device the measuring instrument according to the invention described above offers the advantage that, in a simple manner, compact, high-temperature-capable measuring instruments can be reliably connected with a connection leading to an evaluating circuit without great complexity

REFERENCES:
patent: 3630874 (1971-12-01), Olette et al.
patent: 3758397 (1973-09-01), Rittiger et al.
patent: 3784459 (1974-01-01), Jackson
patent: 4096050 (1978-06-01), Kobayashi et al.
patent: 4116797 (1978-09-01), Akatsuka
patent: 4151503 (1979-04-01), Cermak et al.
patent: 4399017 (1983-08-01), Inoue et al.
patent: 4452687 (1984-06-01), Torisu et al.
patent: 4560463 (1985-12-01), Frey et al.
patent: 4708783 (1987-11-01), Nakamura et al.
patent: 4818364 (1989-04-01), Weber et al.

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