公开(公告)号：EP1766748A4

公开(公告)日：2011-11-16

申请号：EP05739498

申请日：2005-05-17

申请人： ABB OY

发明人： LAAKSO KARI-MATTI ,  BERTS ANDREAS ,  KUIVALAINEN JANNE

IPC分类号： H02H9/04 ,  G01R1/36 ,  H02H20060101

CPC分类号： G01R1/36 ,  H02H9/04

公开(公告)号：EP1779487A4

公开(公告)日：2008-01-09

申请号：EP05751803

申请日：2005-06-08

申请人： ABB OY

发明人： LAAKSO KARI-MATTI ,  BERTS ANDREAS

IPC分类号： H02H1/00 ,  G01K7/16 ,  G01K7/22 ,  G01K7/24 ,  G01K7/25 ,  H02H20060101 ,  H02H7/085

CPC分类号： G01K7/25 ,  G01K7/24 ,  H02H7/0852

摘要： The invention relates to measuring the resistance of a resistive sensor, such as a PTC or NTC temperature sensor used for monitoring the temperature of the windings of an electric motor. The invention is based on an electronic circuit in which conductors from a sensor located in the object to be monitored are connected to an amplifier circuit in a feedback configuration that reduces the DC level supplied to the voltage divider when the sensor resistance increases. The measured signal is amplified and, using a comparator to compare it with the output voltage of a sawtooth generator, a continuous PWM (Pulse Width Modulation) signal is generated and transmitted in digital format to a SELV electronic circuit, for example through an opto-isolator. The essentially logarithmic signal amplification makes it possible to reliably distinguish between a short circuit in the sensor circuit and low values of sensor resistance.