Measuring device for measuring particulate matter concentrations using scattered light and method for monitoring the measuring device

A method for monitoring a measuring unit for measuring a particulate concentration in exhaust gases, the method comprising:

• measuring, using a measuring unit, the particulate concentration in the exhaust gases using scattered light, wherein the measuring unit includes a measuring chamber having at least one light source and having at least one light sensor, the measuring chamber being situated in an optical path of the light source, the light source configured to generate a light beam, which runs in the measuring chamber as a chamber light beam, the light sensor being configured to record the light of the chamber light beam that is scattered in the measuring chamber by particulates of the exhaust gas, and includes a monitoring device to detect an intensity of the chamber light beam in the measuring chamber with the aid of scattered radiation;
• and
• taking a monitoring measurement to detect the intensity of the light beam running in the measuring chamber;
• and
• determining, via at least one evaluation device, the particulate concentration associated with a scattered light member;
• wherein in response to the irradiation using the light beam, the scattered light member generates scattered radiation and an additional light sensor records the scattered radiation generated by the scattered light member,
• wherein the scattered light member generates defined scattering radiation, and
• wherein at a defined intensity of the light beam, the scattered light member supplies the defined scattering radiation at a defined intensity, and
• wherein the at least one light source is a laser light source to generate the light beam which is coupled into the measuring chamber using the defined intensity and runs within the measuring chamber as the chamber light beam, which exits from the measuring chamber as an output light beam which impinges upon a radiation absorber, in which non-scattered or partially absorbed light of the light source is completely absorbed or nullified, and
• wherein the scattered light member is settable into a calibrating device or a scattered light member of a present calibrating device is settable into the monitoring device as the scattered light member,
• wherein there are light sensors in the measuring unit and the at least one evaluation device, so that the light scattered by the scattered light member in the measuring chamber is recordable having scattered light radiations by the light sensors and the particulate concentration associated with the scattered light member is ascertained by the at least one evaluation device, and
• wherein the light source and/or the at least one evaluation device is adjustable so that a specified, known particulate concentration as a result of the calibrating measurement is outputtable by the at least one evaluation device.