Introduction; Intended Use; Functionality; Humidity Monitoring - Bosch Rexroth WGM Operating Instructions Manual

1 Introduction

1.1 Intended use

Oil humidity sensors are used for monitoring the water content in oil and for
temperature measurement. Oil humidity sensors must not be used in highly
inflammable or corrosive liquids.
Observe the technical data in the appendix with regard to the specific intended
use, available material combinations and temperature limits.
All device types are intended exclusively for industrial applications. They
are not safety components. The devices must not be used if the safety and
health of persons is impaired in the event of failure or malfunction.
Any use in potentially explosive areas is inadmissible.

1.2 Functionality

The sensor determines the relative humidity of the oil via the water activity (a
The relative humidity is comparable to the water activity.
This can also be called the degree of oil saturation. The sensor is equipped with a
measuring chamber in which the humid air inside and the humidity in the medium
are in balance. The sensor sets these values in relation to the maximum saturation.
We thus obtain a measure of the oil saturation. Furthermore, the temperature is
recorded to be able to correct the values. Water activity is given as a factor between
0 and 1. Multiplied by 100%, we get the relative humidity or the saturation in
percent.
The critical limit of saturation depends on several plant-specific parameters.
The main advantage, however, is the permanent monitoring of humidity and
temperature. This enables the machine end-user to make own statements about
changes in the plant and to adjust the plant parameters, if required.

1.2.1 Humidity monitoring

The sensor element for determining the humidity is located in the medium and
protected by a protective pipe. The relative humidity can be output permanently
as an analog or digital signal (IO-Link) or executed as a switching signal.
The threshold value is pre-set and can be freely configured depending on the type.
Depending on the version, switching outputs combined with an analog output
(4 - 20 mA) are available. The display options can show the relative humidity on the
display and output it on the analog output. The threshold values of the switching
outputs can be freely configured. The sensor options offer the possibility of an
analog output of the relative humidity. The threshold value of the switching point
is pre-set and can only be configured ex works or via the digital interface.
WARNING
RE 51550-B/09.2019, Bosch Rexroth AG
Introduction 5/46
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