The Metrology Laboratory offers numerous practical experiments which serve to teach students metrology in a practically relevant way, especially the measurement of basic parameters. These laboratory experiments supplement and complement the course content of the accompanying metrology lectures. The laboratory offers up to 6 workstations for teams of up to 2-3 students. Final projects are also carried out in the laboratory.
Contact General Metrology Laboratory / City Campus
The Laser Metrology Laboratory provides students with specialist knowledge on how to use various measurement methods to record vibrations and acoustic parameters. Problems relating to NVH (noise, vibration, harshness) can be addressed with equipment for multi-channel data acquisition, vibration analysis and simulation. The optical methods are used to measure deformation and travel and also to measure component dimensions and for non-destructive testing. Deformation and strain states for dynamic and static loading can be measured and components can be optimised by means of simulation.
Laboratory exercises and projects - General metrology
Rotational speed measurement
Several methods to measure the rotational speed of the shaft are lined up on a shaft driven by a brushless DC motor. The signals output by the sensors are visualised with digital storage oscilloscopes and a frequency counter. The measurement errors of the measurement methods are determined and compared. The ability to measure at low speed or at large distances from the shaft is investigated as well.
The use of various pressure sensors such as piston manometer and pressure balance, liquid U-tube manometer, bellow manometer through to integrated micromechanical membrane sensors to measure absolute and differential pressures in gases and liquids is demonstrated. The sensors must be calibrated with the aid of calibration equipment and their characteristic curves recorded. Terms such as linearity, error classes and hysteresis errors are an essential part of this experiment.
The exercise involves measuring the flow velocity and the mass flow in a fan. The sensors used are turbine flow meters, rotary-vane and hot-film anemometers, differential pressure sensors in combination with standard orifices or pipe bends and the Prandtl (Pitot-static) tube. Pressure, density and temperature must be taken into account.
This experiment uses PTC and NTC thermistors, platinum resistance thermometers, thermocouples with compensation, and conventional as well as computer-aided evaluation. Particular emphasis here is placed on transient behaviour at the sensor, in the processing of the measurement data and at display and registration devices. Measures to allow the faster determination of temperature are explored.
Strain gauge metrology
As part of this experiment, each team of students produces a balance with a measuring range of 0 to 30 kg. All individual steps needed for the application of strain gauges on a cantilever beam, for the zero balancing, and the amplifier calibration of the conventional or computer-aided evaluation electronics must be carried out by the students themselves. In conclusion, the linearity and hysteresis of the balance is reviewed.
Use of measuring data acquisition systems
In this exercise, students familiarise themselves with computer-aided metrology with measurement systems. The students store the data for the sensors in the system. In doing so they take into account the criteria for setting the sampling rate, and the setting of low-pass and high-pass filters. The data collected are processed with the evaluation interface and displayed in graphic form.
This is a project whereby students investigate CAN databus-capable sensors with the aid of software, read out the data and visualise them. The basics of bus systems in the vehicle and the structure of CAN messages are explored by the students themselves.
The students take on projects to work out solutions to metrological problems such as the sealing of cable penetrations against a low pressure in the vicinity of the sensor.
Further topics are the planning of new laboratory experiments and visualisation aids for lecture content such as the representation of a transient of current and voltage in an RC element.
Laboratory exercises and projects - Laser metrology
The experiments are performed by groups of students (2-5 people).
Fundamentals of optics: diffraction, interference
Interferometers, for example, are set up on vibration-isolated tables using lasers and optical components.
Holography / speckle interferometry - Setup to produce a double-exposure hologram - Evaluation of interference lines with an image processing system - Deformation measurement on a pressure vessel - Determination of the resonance frequencies on a gearbox cover - Determination of the operating deflection shapes (ODS) at different frequencies.
- Deformation measurement on a plastic vessel under internal pressure - Testing of a carbon-fibre component for delaminations - Digitisation of a component and export of STL files.
Vibration measurement on the laboratory vehicle with the laser scanning vibrometer
With the engine running, operating deflection shapes are measured on the vehicle underbody and the exhaust system.
Sensors/excitation of vibration
Various sensors (acceleration sensors, microphones, ...) are calibrated, various types of vibration excitation with electrodynamic shakers are compared (sinusoidal, periodic chirp, noise,...).
Resonances and operating deflection shapes
An impact hammer and acceleration sensors are used to determine the resonance frequencies and associated operating deflection shapes on a gearbox cover.
As the engine of the laboratory vehicle is being revved up, deflection shapes and resonance frequencies are determined on the vehicle underbody (waterfall charts) by means of a multi-channel acceleration measurement.
Sound intensity measurement
For a loudspeaker system, a sound intensity probe is used to determine the frequencies emitted at the different loudspeakers.
Modal analysis and simulation
The modal deflection shapes on a component are determined by simulation and the measurement data are compared with the results of the modal analysis.
Laboratory equipment General metrology
14 laboratory measurement benches with power supply, some with compressed air connection; WiFi connection.
Rotational speed test bed: brushless DC motor, speed controlled, 0-4,000 rpm
Fan test bench: aspirating blower with controlled blower speed. Mass flow from 100 kg/h to 750 kg/h
Several experimental set-ups for small groups of 2 to 3 students relating to temperature, pressure, flow, transient phenomena, acceleration, and evaluation of load cells on cantilever beam basis.
» Vibration analysis, acoustics (NVH)
Experimental modal analysis
Operating deflection shape analysis
» Optical methods
Laser scanning vibrometry
Holography, speckle interferometry
Gray code method
» Equipment deformation and vibration measurement and shaker test
Laser speckle interferometry with CW laser 1D and 3D
Research project: COMPUTATION OF THE ACOUSTIC BEHAVIOUR OF AN ELECTRIC ENGINE
The steady increase in the demands being placed on the comfort provided by today’s vehicles means that topics are becoming important in modern development which used to play more of a subordinate role in the past. A typical example for this is the acoustic behaviour of a drive. This specialist field is also called Noise-Vibration-Harshness (NVH). Since engines are becoming quieter and quieter, different methods must be used to analyse and assess the NVH behaviour. The aim is to use the investigations as the basis for the early detection of irritating or unpleasant noises occurring when the vehicle is in operation and to carry out appropriate countermeasures.
Work on this topic is undertaken within the framework of the Hybrid II collaborative doctoral programme.