Introduction to Dual-Channel Fault Simulator for Oxygen Sensors
The new dual-channel oxygen sensor fault simulator from Global Electronics, Ltd is designed to test the automotive On-Board Diagnostic (OBD) monitor responsible for detecting faults in the engine’s air-fuel control system. Specifically, this device modifies the signals of new exhaust gas oxygen sensors (“switching-type”) so as to mimic the slower response often seen in aged sensors, which increase emissions by virtue of their poor response time. By enabling user-controllable “degradation” of the O2 signals, this box allows verification of compliance with mandated OBD requirements for this sensor.
This box is very similar to the previous single-channel O2 fault box from Global, except for a few software improvements and the addition of a second channel to allow signals from two oxygen sensors to be degraded simultaneously. (Two oxygen sensors are used ahead of the catalyst for V-configuration engines.) However, a much older version of O2 fault box (pre-2008) from Global Electronics, recognized by the absence of an LCD screen, is quite different from the current device described here.
Automotive fuel control typically has used “switching-type” oxygen (O2) sensors, though another type of oxygen sensor (known variously as “wideband”, “universal”, “non-switching”, etc.) has become popular recently. Global’s O2 fault simulator is designed for, and works only with, switching-type oxygen sensors.
Simulation of aging sensors is achieved via six different modes of slow response, each with an adjustable amount of degradation. Three of these modes involve a time delay from the input signal to the output (“degraded”) signal: delay for rising transitions only, falling transitions only, or both transitions. The other three modes do not delay the onset of transition, but slow down the time required to complete the transition (as from a low-pass filter): filter applied to rising transitions only, falling transitions only, or both transitions.
In addition to the six types of slow response, the box also can apply an adjustable offset (position or negative) to the signal, simulating drift in offset voltage of aged sensors.
All such degradations are applied equally to both channels of O2 signals, with the exception that if either of the two toggle switches is set to “bypass”, the corresponding channel’s O2 signal is sent directly to its output without degradation.
The box is powered by 12 V from an external source.