Method of monitoring rpm sensors

• US 5,579,235 A
• Filed: 10/07/1994
• Issued: 11/26/1996
• Est. Priority Date: 04/07/1992
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Dittmar, Christian, Schlichenmaier, Andreas, Schwabe, Ulrich, Blanc, Martin, Haefele, Klaus, Purat, Thomas
• Primary Examiner(s): Trammell, James P.
• Application Number:
  US08/318,740
• Time in Patent Office: 781 Days
• Field of Search: 364/481-487, 364/551.01, 364/426.02, 303/122-122.15, 388/831, 363/50
• US Class Current: 702/64
• CPC Class Codes: G01P 21/02 of speedometers

Abstract

A process for monitoring several inductive rpm sensors includes superposing a direct current voltage on an alternating voltage signal from one rpm sensor in one rpm sensor circuit to form a combined voltage signal and monitoring a voltage level of the combined voltage signal at a monitoring point in the one rpm sensor circuit to detect a fault such as a break in a sensor feed line. To detect short circuits between rpm sensors and/or their feed lines, the process also includes changing the voltage level at the monitoring point of the one rpm sensor by feeding a test voltage pulse to a pole of the one rpm sensor during a predetermined time interval in a test stage and monitoring a voltage level at a monitoring point of at least one other rpm sensor and/or its feed lines in at least one other rpm sensor circuit to determine if a change in the voltage level at the monitoring point of the at least one other rpm sensor occurs during the predetermined time interval in which the voltage level is changed at the monitoring point of the one rpm sensor in the one rpm sensor circuit.

Claims

1. In a process for monitoring a plurality of rpm sensors, said process comprising the steps of superposing a direct current voltage on an alternating voltage signal from one rpm sensor in one rpm sensor circuit to form a combined voltage signal and monitoring a voltage level of the combined voltage signal at a monitoring point in the one rpm sensor circuit to detect a fault, the improvement comprising changing the voltage level at the monitoring point in the one rpm sensor circuit by feeding a test voltage pulse to a pole of the one rpm sensor during a predetermined time interval in a test stage;

and monitoring a voltage level at a monitoring point of at least one other rpm sensor in at least one other rpm sensor circuit to determine if the voltage level at the monitoring point in the at least one other rpm sensor circuit changes during the predetermined time interval in which the voltage level is changed at the monitoring point in the one rpm sensor circuit and thus to determine when a short circuit exists between the at least one other rpm sensor and the one rpm sensor.

2. The improvement as defined in claim 1, further comprising not monitoring the one rpm sensor circuit to detect said fault during the predetermined time interval but performing said monitoring of the one rpm sensor circuit for said fault prior to said predetermined time interval.