Frequency Test Stand | VTS


Software controlled hydraulic clamping

Resonance measurement with high resolution

Blade database

Easy to use

Export to Excel, ASCII or SAP

Scalable for different blade sizes

These test stands are developed for high resolution determining of blade resonances. Especially the influence of the clamping of the blades was minimized to guarantee high repeatability.

Cost and time reduction

By easing the operation of the software and a high safety level it is possible that normal workers can do the measurements of the test objects. This leads to a reduction of costs and enables the test in the production line. The deviations from the tolerances are detected very early and bad parts can be sorted out. To reach this goal the automation of the following steps was done:

Hydraulic clamping

Automatic resonance determination

Test piece management (Blade database)

With this support a measurement is done with a few mouse clicks.


The blade is excitated with an impact hammer and the vibration answer is measured with a microphone or a laser. A high precise data acquisition system ensures the accuracy of the measurement.


The main focus during the development was to create an easy to use and very functional software. The result is a program that can be used for nearly every quality test. The following key features are available:

Sequential measurements (including master blade measurements)

Determining the mode shapes

R&D test measurements

Sequence management

With this support a measurement is done with a few mouse clicks.

Test item management (Blade management)

Analysis & reportsr

User & right management

All setups and measurement data are saved in an local data base, but can also be stored on an main server. The export to Excel or SAP is implemented and with the “Office-Function” it is possible to setup the parameter or define or edit the test sequences form the office PC via the network.


Components test for gas turbines

Compression blades

Turbine blades

Standard Teststand

Maul-Theet offers three different standard configurations for determining the natural frequencies. In addition, inputs for pressure and temperature measurement are available.

1.VTS stand alone

This solution includes all equipment required for the vibration measurement (modal hammer, sensors, data acquisition) as well as a PC with software. It is independent of the clamping device or excitation. As soon as the clamping force has been confirmed, it is possible to start the vibration measurement and the determination of the resonance frequencies. The data can be saved and reports generated.

2. VTS with manual hydraulics

This solution includes a manually operated hydraulic unit. It is integrated in a test bench made of aluminum profiles, which also houses the clamping unit. The design of the test bench can be adapted to the customer’s application. The clamping force can be adjusted via a toggle switch. It is possible to measure the clamping force with the VTS controller and display it in the VTS software. For clamping forces outside the permissible range, the vibration measurement is automatically blocked by the VTS software.

3. VTS with PLC controlled hydraulics

This solution has a PLC control of the hydraulic unit. The PLC controls the proportional valves to preload, tension and control the clamping force during vibration measurement. The pressure accumulators ensure that the clamping forces remain stable for up to 20 minutes without pump operation during experimental measurements. With PLC-controlled hydraulic clamping forces of up to 650 kN are possible.

VTS test stand configurator

TeststandExcitationClampingVibration SensorMonitoring Sensor
VTS Stand AloneHammer without force cellCustomized
MicrophoneClamping pressure (optional)
Hammer with force cellLaser (LDV)Temperature (optional)
Automatic hammerMicrophone
VTS with
manually hydraulic
Hammer without force cellHydraulic manually controlledMicrophoneClamping pressure included
Hammer with force cellLaser (LDV)Temperature (optional)
Automatic hammerMicrophone
VTS with PLC controlled hydraulicHammer without force cellHydraulic controlled by PLCMicrophoneClamping pressure included
Hammer with force cellLaser (LDV)Temperature (optional)
Automatic hammerMicrophone