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TM 155 Free and forced vibrations



  • Demonstration of fundamental aspects of mechanical vibration1
  • Damping and resonance with forced vibrations
  • Two different principles of exciting vibration


Technical Description

All setups of this experimental unit on the theory of vibrations are rapidly and securely assembled on a double profile frame made of aluminium using slot nuts and clamping levers. The oscillator consists of a beam mounted in ball bearings at one end; a helical spring is hung on the other end of the beam. The attachment of springs, the exciter and a damper to a perforated panel permits a wide range of different setups to be reproduced. Either an unbalance exciter or a displacement exciter generate vibrations; the frequency of the vibrations can be adjusted using the electronic control unit. The displacement exciter can be fitted directly to the base of the spring. The vibrations can be damped using the adjustable viscosity damper. To record vibration processes over time, a mechanical drum plotter is included.

The experiment also includes an amplitude contact with a TTL output, e.g. for triggering stroboscopes.

The measured values can be evaluated with the software for data acquisition TM 155.20. A practice set for torsional vibrations (TM 150.02) is available as accessories.

Learning Objectives / Experiments

- natural vibration
- damped vibration
- inertia force and displacement excitation
- forced vibration
- resonance
- amplitude and phase response


[1] basics of mechanical vibration, natural damped and forced vibrations
[2] bar-type oscillator 
[3] three helical springs 
[4] unbalance exciter with DC motor, 0,77kg
[5] displacement exciter with DC motor
[6] electronic control unit with digital display, exciter frequency adjustable
[7] oil-filled damper
[8] electrically driven drum recorder
[9] amplitude meter with electric contact for triggering equipment
[10] storage system to house the components

Technical Data

Bar-type oscillator: LxWxH: 700x25x12mm, 1,6kg
Helical springs
- 0,75N/mm
- 1,5N/mm 
- 3,0N/mm
Exciter frequency: 0...50Hz, electronically controlled
Unbalance of the unbalance exciter: 0...1000mmg
Stroke of the displacement exciter: 20mm
Damper constant: 5...15Ns/m, oil-filled
Mechanical chart recorder

- feed: 20mm/s
- paper width: 100mm

Dimensions and Weight
LxWxH: 1000x420x900mm
Frame opening WxH: 870x650mm
Weight: approx. 52kg
LxWxH: 1170x480x237mm (storage system)
Weight: approx. 12kg
Required for Operation 230V, 50/60Hz, 1 phase or 120V, 60Hz/CSA, 1 phase (control unit)

Scope of Delivery
1 frame
1 bar-type oscillator
3 helical springs
1 unbalance exciter
1 displacement exciter
1 exciter control unit
1 damper
1 amplitude meter
1 drum recorder
1 storage system with foam inlay
1 manual

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