Page 271 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Chapter 2.2

Nissan Motor Co.

The method of GB1373826 (1974) comprises a thermocouple comprising two wires having
terminals connected to each other so as to form detecting junctions which are positioned
upstream and downstream of the catalytic converter respectively, and an ampere-meter
measuring the difference in temperature between the two measuring points. When the
difference in temperature between downstream and upstream catalytic converter temperature
indication is lower than a predetermined value then the catalytic converter is considered as
deteriorated.

The method of DE2346425 (1974) comprises the following steps:
1) measuring the temperature of exhaust gas at the inlet port of the converter by means of a
first temperature sensor which produces a signal analogous to the temperature
2) measuring the temperature of exhaust gas at the outlet port of the converter by means of a
second temperature sensor which produces a signal analogous to the temperature
3) producing an operating temperature signal when the voltage of the inlet temperature signal
exceeds a first predetermined value
4) producing a difference signal analogous to the difference between the inlet and outlet
temperatures of the converter as represented by the inlet and outlet temperature signals
5) producing a failure signal when the voltage of the difference signal is below a second
predetermined value
6) producing an alarm signal when the operating temperature signal and the failure signal are
applied simultaneously thereto

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