Reduction of Temperature Dependent Drift in On-Line Wear Debris Hall Effect Sensor

Abstract

In this work, efforts have been made towards finding suitable techniques of minimizing output drifts in the operation of an online wear debris Hall Effect sensor. Hall chip (with an ALNICO permanent magnet) output fluctuates at a rate of about 1mV per a degree change in Celsius. This was observed whenHall sensor chip (HAL815) was used with an ALNICO permanent magnet to build a wear debris sensor for machine condition monitoring. Other chips have been tested such as HAL825 but the variation was still found to be within that range under similar conditions. Tests carried out in this work indicated that any kind of noise reduction technique must have some form of impact on the stability of the magnet since it has been found to be a major contributor to the drifts in the system due to hysteresis over temperature fluctuation. All the tests were carried out by placing 80mg wear debris on the sensor head in an environmental chamber connected to a LABVIEW MMI (man-machine interface) and LABVIEW was used for all simulations and data acquisition. Several techniques of strengthening signal to noise ratio as well as noise reduction schemes have been investigated such as: Calculated output correction, environmental monitoring/control, use of low noise electronic components and method of opposing environmental input (differential method). Opposing input (differential) technique was found to be the most stable drift correcting method on this device as drift was reduced to about 0.1%fsd over temperature variation from 10˚C - 60˚C thus improving the stability of operation of the sensor.