摘要 |
An exhaust oxygen concentration measuring device comprises a diffusion chamber 46 and solid electrolyte to measuring 44,45, and oxygen pumping 41,42 portions. The measurement voltage is composed with a reference voltage Vf and the difference signal is used both to control the pump current via 64 and Ry1 and as an input to the fuel control system. The condition of the measuring device is supervised at 66 by detecting an abnormal condition if the measurement voltage either exceeds a first threshold level or is below a second threshold level. On detection of an abnormal signal, the pump current is switched off by Ry1 and a backup signal representing a standard oxygen concentration if fed to the fuel control system by Ry2. <IMAGE>
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