MMF M72 Series Charge or IEPE Conditioners Instruction Manual

MMF M72 Series Charge or IEPE Conditioners

Application

The M72 Series Signal Conditioners are intended for connection of piezoelectric acceleration, force or pressure transducers. The input is suitable for sensors with charge output as well as for IEPE compatible transducers and microphones.
The M72 enables optimal adjustment of the sensor signal to existing measuring equipment or PC-based data acquisition systems. The Signal Conditioners provide the following functions:

• Adaptation of the sensor signal and sensor supply
• Amplification
• High- and low-pass filtering (for example anti-aliasing filter)
• Integration of the sensor signal, for instance, to measure velocity or displacement.

The instruments all have a robust aluminum housing making them suitable for work in the laboratory as well as under field conditions.
The following model variants are available:

Function and Operation

Figure 3 illustrates the most important functional groups of M72 in a block diagram.

All functions are controlled by a microcontroller.
Depending on the position of the input switch, the input signal passes the impedance converter Q1 or Q2. If IEPE operation has been selected, the signal is transmitted to the amplifier via a buffer stage. During IEPE operation a constant current is fed into the input socket to supply the sensor electronics. With the M72Ax and M72S1 instruments the stored electronic data (TEDS) of selected IEPE sensors can be read out. If an AC voltage supply is to be connected to the input, the constant current supply can be switched off.
The input circuit is followed by the first amplifier stage, low pass and high pass filters. The high pass filter can be switched between 0.1 Hz and 3 Hz. The low pass filter has 4 frequency limits to choose from, including 0.1 / 1 / 10 / 50 kHz.
The sensor sensitivity of M72Ax and M72S1 can be entered to achieve finely tuned amplification. To aid this there is an adjustable damping stage after the filters.
The single and double integrators can be switched on to measure velocity and displacement, respectively.
A second amplification level follows subsequently. Due to the distributed amplification before and after the filter there is an overload reserve which is also applied to signal components outside of the filter or the integrator pass band. Simultaneously a high signal-to-noise ratio is achieved.
Before the output socket there is a driving stage with low pass filters to reduce disturbance. The output is DC coupled.
The overload LED lights up when the output signal is over 90% of the full modulation. It also signalizes the occurrence of overload before and after the filters and integrators.
The M72Ax and M72S1 instruments have a digital display which shows the modulation at the output as a percentage of the maximum value.
All settings are configured via the buttons. Five seconds after the last press of a button the instrument saves the current settings. This means that the last operating status remains even after the instrument has been switched off and on again.
The units with display M72Ax and M72S1 show the hardware version and the software version for one second each, after switching them on.

Power Supply and Mass

Grounding Concept
The inputs and outputs of the signal conditioners are single-ended, i.e. asymmetrical. The signal ground is connected to the outer conductor of the input and output sockets.
The instrument housing is internally connected to ground.
The power supply is signal-referenced, i.e. the negative terminal is connected to ground.

External Power Supply
The M72 Signal Conditioners are powered by an external DC voltage
A mains plug adapter for 115/230 V AC with 12 V output voltage is supplied with the Signal Conditioners M72Ax and M72Bx. The power supply socket according to DIN 45323 is located at the rear of the instruments. Any DC voltage source of 7 V to 28 V DC and around 250 mA (for M72x1) or 750 mA (for M72x3) can be connected to this socket. The positive supply terminal is connected to the center pin (tip). The ON/OFF switch is located at the rear.
Models M72R1 and M72S1 are powered from the rack cases M72R8 or M72S8 via a 9 pin D-Sub connector at the rear side of the modules.

Sources of Errors

• Avoiding Ground Loops
  Earthing or ground loops are often the reason for measuring errors in multichannel measuring systems. In most cases you will find a superimposed 50 (60) Hz or 100 (120) Hz voltage on the measuring signal. One reason for this effect may be that the transducers are ground referenced not only via their cable at the signal conditioner, but also at the measuring point through their housing. Vibration transducers are often mounted at grounded machine parts. Within earthing systems transient currents may appear. These transient currents cause a potential drop across the earthing or grounding wires. Via the signal input of the amplifier they may result in a considerable measuring error. To avoid this, insulated attachment of the transducers is recommended. Metra offers several industrial vibration transducers with an insulated mounting base and different insulating flanges for non-insulated sensors. A star-shaped grounding network is the ideal solution to avoid ground loops. Star-shaped means that all grounding wires of the sensors and the amplifier outputs are tied to ground at the signal conditioners, without any transverse connections. In many cases this is more difficult to realize for the outputs than for the inputs, because the subsequent measuring equipment may have sin- gle-ended inputs. If you have the choice of using differential inputs, which can be found on many data acquisition boards, you should preferably use them.

• Low-Frequency Noise
  When the M72 is used with high gain and with the lower frequency limit of 0.1 Hz (high pass off) it may be sensitive to temperature transients. Even draft may result in output voltage fluctuation of some hundred millivolts at frequencies around 0.1 Hz. To reach thermal balance a warm-up time of some minutes is recommended before measurement. For measurements outdoors it may be advantageous to isolate the device by foam rubber or similar materials.
  Piezoelectric sensors have the so-called pyroelectric effect which may cause similar disturbances. This phenomenon is particularly strong with compression- type and bending type (beam) transducers. Here it is also important to maintain stable temperatures.
  If lowest frequencies are not of interest the 3 Hz high pass should always be used. With the integrators (see Chapter 8.3.) the 3 Hz high pass is always on.

Inputs

The Signal Conditioners M72 are designed for both sensors with charge output and sensors with integrated impedance converters to IEPE standards. Both input types use the same BNC input socket. Select the input type by pressing the “Input” button repeatedly. The current status is indicated by a blue LED for charge input or white for IEPE. If neither of the LEDs are lit, the instrument is running as a voltage amplifier without IEPE power supply.

Charge Input
Capacitive signal sources, usually piezoelectric sensors with charge output, are connected to the charge input. The input stage is a capacitive feedback amplifier, which transforms the sensor charge signal into a voltage. The ratio of output charge (U) to input charge (Q) is determined by the capacitance of the feedback amplifier (C).

The M72 Signal Conditioners have two charge converter stages. At the lowest gain range a charge converter with a gain of 0.1 mV/pC is used. For the other gain ranges a charge converter with 1mV/pC is active. To ensure that the output charge reverts to zero after a specified period of time without a charge signal, discharge resistors are located over the feedback capacities. The resistors are designed in such a way that a lower frequency limit of 0.1 Hz is obtained. This makes manual reset no longer necessary. The advantage of charge measurement is that cable capacitance and insulation resistance have almost no influence on the measuring results. For sensors with charge output it is strongly recommended to use special low-noise cables. Ordinary cable will cause a considerable measuring error under mechanical stress, as a result of the so-called triboelectric effect. Cables with low insulation resistance, for example caused by humid connectors, reduce the accuracy of measure-ment at lower frequencies. A desirable insulation resistance is higher than 10 GW. Cables longer than 10 m are not recommended at the charge input. Proper shielding is also important.

IEPE Input
IEPE stands for “Integrated Electronics Piezo Electric”. It has been established as the industrial standard for piezoelectric transducers. Other brand names for the same principle are ICP®, Isotron®, Deltatron®, Piezotron® etc. The integrated sensor circuit transforms the charge signal of the piezo- ceramics, with its very high impedance and high EMI sensitivity, into a voltage signal with low impedance. The converted signal can be more easily transmitted. At this signal ordinary low cost coaxial cable with a length of more than one hundred meters can be used. A peculiarity of IEPE is that power supply and measuring signal use the same line. So, an IEPE transducer needs, like a transducer with charge output, only one single-ended cable. Figure 4 shows the block diagram. To separate the low impedance sensor signal from the power supply, the integrated circuit is supplied with constant current. This constant current must be fed into the measuring line and simultaneously separated from the subsequent amplifier stages.
The flow of constant current into the sensor it is indicated by the permanently lit white LED “IEPE”.

By supplying the sensor with constant current a positive DC voltage arises over its terminals. This bias voltage depends on manufacturer and specimen and is usually between 5 and 15 V. The sensor signal is superposed on this bias voltage. The output voltage of the transducer never changes to negative values. Its minimum value is the saturation voltage of the integrated impedance converter (0.5 V to 1 V). The supply voltage of the constant current source determines the maximum value of the output voltage. For the M72 this voltage amounts to 24 V and guarantees an optimum dynamic range for all available sensors. Figure 5 shows these relations.

The M72 uses the bias voltage for an IEPE functional check. Sensor errors are indicated as follows:

• quick flashing (ca. 4 Hz) of white LED: IEPE bias voltage < 1 V
  • short circuit in the sensor cable or sensor
• slow flashing (ca. 1 Hz) of white LED: IEPE bias voltage > 20 V
  • open input or disconnected cable

Switching Off the IEPE Power Supply
In some cases it may be necessary to switch off the IEPE constant current supply in order to use the IEPE input as a regular AC input. In this case, press the “Input” button repeatedly until the blue and white LEDs switches off.
The input resistance of the amplifier is approximately 10 MΩ.

Amplifier

The M72 Series instruments have the following gain ranges:

• Charge mode: 0.1 / 1 / 10 / 100 / 1000 mV/pC
• IEPE mode: 1 / 10 / 100 / 1000 times or 0, 20, 40 and 60 dB.

The gain can be selected using buttons “Gain +” and “Gain -”.
After switching the input the lowest amplification is automatically configured. After connecting a sensor and sometimes after changing the measuring range, the amplifier needs a certain settling time because of short term overload. In this case it may take up to 30 seconds until the output voltage is free from DC components. The amplifier output is buffered and DC coupled. Potential offset currents, which may subsequently be fed into the amplifier output by equipment such as a PC data acquisition board, do not cause a DC offset at the output.

Transducer Sensitivity (M72Ax / M72S1)

The output voltage of the M72Ax and M72S1 instruments can be scaled to result in a decimal ratio between the output voltage and the mechanical measurement quantities, for example 100 mV/ms-2 or 1 V/Pa. By this means a measuring chain will always yield the same output voltage per mechanical unit, independently of the sensor type. To ensure these results the transducer sensitivity, also called the transfer factor, is required. In the case of accelerometers with charge output this is the charge transfer factor Bqa, and for IEPE accelerometers it is the voltage transfer factor Bua. The charge transfer factor is stated on the calibration certificate or the sensor data sheet.
The transducer sensitivity can be entered in two ways:

1. Manually: to enter the sensitivity manually press ▲ or ► to switch from the modulation display to the sensitivity display. By pressing the button ► again the decimal point moves position. Press ▲ to increase the digits left of the decimal point by one. Enter all four sensitivity decimals consecutively. After this, position the decimal point to the right by pushing the button ►.
2. Automatically: when connecting a transducer with an electronic data sheet (TEDS) to IEEE 1451.4 (Templates 25, 27 or 28), the sensitivity is read automatically and appears briefly on the display.

The most recently entered sensitivity can be viewed at any time by a short press of ▲ or ►. It is also saved when the instrument is switched off. By entering the sensor sensitivity (B) the selected gain (G) of the M72 is multiplied by a correction factor (K). The total resulting gain (Gtot) is:
Gtot= B ⋅K ⋅G

The correction factor (K) is calculated from the entered transducer sensitivity. In this calculation the decimal point is moved to give a numerical value of between 1 and 10. Then the reciprocal value is calculated. For this reason, the correction factor can only take values in the range of 0.100 to 1.000. Consequently, the entered position of the decimal point for the sensitivity has no effect on the gain. The decimal point only provides the entry position and displays the transducer sensitivity. Even leading zeros have no influence. In this way, for example, the input of “2.570” results in the same gain as “025.7”. It is nevertheless important to enter all known decimals. Of most relevance to the user is the ratio between the output voltage and the measured mechanical quantity. For example:
The sensitivity of an accelerometer is Bqa = 18.25 pC/ms-2. The selected gain is V = 100 mV/pC. The calculated correction factor is

Level Indicators
The red LED “Overload” warns of signal clipping by high magnitudes. The indicator switches on at around 9 V peak voltage. At 9 V the output signal is still without distortion, however, it is close to the limit. The overload detector monitors the signal level at both the output and before the filters and integrators (see Figure 3). This ensures that high signal components occurring beyond the filter pass band are indicated, even though they do not appear at the output. In addition, the M72Ax and M72S1 instruments display the modulation level via the digital sensitivity display if neither ▲ nor ► have been pressed for more than 5 seconds. The modulation is displayed as a percentage of the peak value (0 – 99 %). The display is updated every 5 seconds. For display values of over 80 % the gain should be decreased and for under 6 % it should be increased to yield an undistorted low-noise signal.

Filters and Integrators

Low Pass Filter
To eliminate disturbing noise or to comply with the Shannon theorem, it can be advantageous to use a low pass filter.

The M72 Series instruments have four internal low pass filters. To select the filter press the “low pass” button consecutively. The selected -3 dB frequency limits are indicated by four green LEDs in kilohertz.
The corresponding 10 % – limits are shown in the following table:

The M72 has fourth-order Butterworth filters. The slope of the low pass filters is over 75 dB per decade. The frequency response is shown in 6.

High Pass Filter
The M72 Signal Conditioners have a high pass filter with a lower limiting frequency of 3 Hz (-3dB). This eliminates low frequency noise which may otherwise occur with piezoelectric compression accelerometers under the influence of temperature transients (see Chapter 3.3.2). The second-order Butterworth filter has a slope of 40 dB / decade. The 3 Hz high pass is switched on and off by pressing the “HP/Integrator” button. When the high pass is switched on the green LED “3 Hz” lights up. When the integrators are in use the high pass is always active. If the high pass filter is switched off the minimal lower limit frequency of the amplifier, 0.1 Hz (-3 dB) is available.
The frequency response is shown in Figure 6.

Integrators
The M72 Signal Conditioners can measure non-integrated, single and double- integration sensor signals. Integration is particularly useful for vibration measurement with accelerometers on rotating machinery. Single integration of vibration acceleration generates velocity, whereas double integration generates displacement. The “HP/Integrator” button activates the integrators. Single integration is indicated by the orange lit LED “Vel.” (velocity) and double integration by the orange lit LED “Disp.” (displacement). If there are no integrators in use then both lights remain switched off. When the integrators are switched on the 3 Hz high pass filter is always activated. The crossing point of the of the frequency response graph with and without integrators is 15.92 Hz (see Figure 6) The following calculations show how the M72 output voltage uout relates to the three vibration quantities, whereby the M72 configured voltage gain Gu in mV/mV and the sensitivity of the accelerometer Bua (see data sheet) is:

The above equations apply to IEPE compatible accelerometers. Accelerometers with charge output are calculated in the same way with charge amplification Gq in mV/pC and the charge transfer factor Bqa of the transducers in pC/ms-2..
Example:
With an accelerometer which has a sensitivity of Bqa= 5 pC/ms-2, the velocity should be measured. The M72 operates with a charge amplification of Gq= 100 mV/pC. At the output a voltage of uout= 300 mVRMS arises. How great is the measured velocity v?
Solution:

The sensitivity settings (see Chapter 6.) of the M72Ax and M72S1 instruments are also applied to the integrators. At frequencies above 15.92 Hz the integrators generate smaller signal amplitudes due to their damping behavior. As a result of this the modulation declines, as does the signal to noise ratio. As a guide value single integration should only be applied to frequencies up to 1000 Hz, and double integration up to 200 Hz. For frequencies below 15.92 Hz, added gain occurs. In the case of double integrators this can be up to 12 times and cause the amplifier output to overload. Overload may occur if there are larger signal components at high frequencies. Despite the fact that the output voltage is not overloaded as a result of integrator damping, the integrator input can nevertheless overload.
The integrator frequency response curves are shown in Figure 6.)

Keypad Lock
To protect the instrument from unwanted or unauthorized operation, the keypad lock can be activated. To activate the keypad lock, hold down the “Input” button for 5 seconds when switching on the power supply voltage. Now, the instrument will no longer respond to the press of a button. The keypad lock is deactivated by switching the instrument on and off again.
For M72R1 and M72S1 the keypad lock can also be activated via the USB interface (see Chapter 11.).

Check and Calibration

We recommend calibrating your instrument at two year intervals. Inside the housing there are no calibration points. All configuration is carried out via an internal serial interface. Metra provides a factory calibration service in conformity with the reference standards of the German National Metrology Institute PTB (Physikalisch-Technischen Bundesanstalt). Alternatively, our instruments may be calibrated in other calibration laboratories which carry out the necessary checks and settings. Upon request Metra will provide a USB adapter cable and instructions for the calibration proce-dure.

Control via USB (M72R1 / M72S1)

Rack M72R8 and M72S8
The 19” rack enclosure can house up to eight M72R1 or M72S1 modules. The power supply is fed through the 9 pin D-Sub socket at the back of the amplifier modules (Figure 9). This socket also provides a serial RS-232 interface for communication with the rack enclosure. All functions of the amplifier modules are controlled via the USB port at the rear of the rack enclosure.

The power supply socket is also located at the rear side of the rack enclosures. It is a circular DC power connector for the supplied mains plug adapter or another DC source with 8 to 28 V and 2 A.

For vertical use of the rack enclosures M72R8 and M72S8 an optional pair of tower feet is available (Figure 7). For later attachment of the tower feet remove the left two plastic caps from the front side of the rack enclosure and unscrew the aluminum cover (Figure 10). Slide out the two plastic strips and slide in the two tower feet instead.

USB Interface
The M72R1 and M72S1 modules are configured within the rack enclosures M72R8 or M72S8 via a USB interface.
The first time you connect the rack casing to a PC you will be asked to install the device driver. The driver data file “MMF_VCP.zip” is located on the internet site
http://www.mmf.de/software_download.htm#m72. Unzip and save both of the enclosed files to a directory on your computer. This directory will need to be entered when windows asks you for the device driver. The provided driver is signed and can run in Windows XP, Vista, 7, 8 and 10. The computer will install a virtual COM port which runs in CDC mode. The advantage of the virtual COM port is that the modules can be controlled via ASCII commands in an uncomplicated manner. Several rack enclosures can be connected to a PC at once, however, each rack enclosure requires its own USB port. The addressing is carried our via a switch at the back of the rack enclosures. The configuration is hexadecimal from 0 to F.

Interface Commands
All commands are structured as follows: #RMx..x The commands always begin with a hash symbol followed by the address (R) of the rack enclo-sure (0 to F). Next the address of the module (M) appears at its location in the rack enclosure. The address of the left module is 0 and the right module 7. Next, the actual commands appear (x). A command is saved when the symbol is sent. Permitted commands with valid parameters are acknowledged by /a. If a command is incorrect the answer is /n. The M72 also answers with /n if a timeout occurs, i.e. if no is received within 100 ms after the last character (from version 001.006). The following commands are supported:

• #RMBnnnnnnnnnnnnnnnnnnnn: write device name
  • n: name (exactly 20 capital letters, spaces or numbers) command acknowledgment: /a
  • error at invalid parameters: /n
  • Send example: #B1BMEASURING POINT NO 1
• #RMD: set default parameters
  • command acknowledgment: /a
• #RME: save all settings to non-volatile memory (from version 001.005)
  • command acknowledgment: /a
• #RMGg: set gain
  • g: gain 0: 0.1 (only with Q); 1: 1; 2: 10; 3: 100; 4: 1000
  • command acknowledgment: /a
  • error at invalid parameters: /n
  • Send example: #11G1 (Gain = 1)
• #RMHh: high pass/integrator on/off
  • h: 0 : high pass off; 1: high pass on; 2: single integrator; 3: double integrator
  • command acknowledgment: / a
  • error at invalid parameters: /n
  • Send example: #10H0 (high pass off)
• #RMIi: select input
  • i: 0 : charge input; 1: IEPE input; 2: voltage input (without IEPE supply)
  • command acknowledgment: /a
  • error at invalid parameters: /n
  • Send example: #21I1 (IEPE input)
• #RMKk: keypad lock on/off
  • k: 0: keypad lock off; 1: keypad lock on
  • command acknowledgment: /a
  • error at invalid parameters: /n
  • Send example:
• #RMLl: select low pass
  • l: 0: 0.1 kHz; 1: 1 kHz; 2: 10 kHz; 3: 50 kHz
  • command acknowledgment: /a
  • error at invalid parameters: /n
  • Send example: #B5L3 (50 kHz)

Setup Tool for M72R8 / M72S8 Rack Cases
The PC software tool is intended to set the M72R1 and M72S1 Charge / IEPE Signal Conditioners in M72R8 or M72S8 rack cases via USB. All settings of the signal conditioners can be controlled from the PC. The settings can be saved to and restored from files. The program is compatible with Windows XP, Vista, 7, 8 and 10. Please download the zip compressed file m72x8.zip from our web page http://mmf.de/software_download.htm#m72 and unzip it on your PC. In the extracted folder start setup.exe and follow the instructions. You may change the installation folders but in most cases the default folders can be used. In addition to the program the LabView runtime environment from National Instruments will be installed (if not done yet) which may take some time. Go to the start menu of your PC and click under Programs / Metra Radebeul on VS1x. The program window opens as shown in Figure 11.

The rack case M72R8 or M72S8 should now be connected to the PC and the device driver installed as described in section 11.2.. When the driver is properly installed each rack case will be automatically assigned to a virtual COM port. The COM port number can be seen in Windows under Control Panel / System / Device Manager. Several rack cases can be operated on one PC by using different USB ports or a USB hub. Each one will be assigned to an individual COM port. Select the virtual COM port of the rack case in the pull-down menu USB/COM port of the setup program. Enter the Rack Address (0 to F) as adjusted by the DIP switch on the rear panel of the rack case. Now a connection to the rack case and its modules can be established. Click Read Settings to transfer the current settings of the 8 modules in the addressed rack case. The modules from the left to the right are numbered in the software as Channel 0 to Channel 7.

Figure 12 shows the program window with the settings for eight modules. The eight channels of the addressed rack case are listed in rows. In the column Input you can select the input type. The types Charge, IEPE and Voltage are available. Under Gain the amplification is set for each module. The gain can be 0.1 (only for charge), 1, 10, 100 and 1000. Under Integrator / High-pass you can select acceleration from 0.1 or 3 Hz, velocity or displacement. Four Lowpass filters of 0.1, 1, 10 and 50 kHz are selectable. Transducer Sensitivity is entered as 4 digit number with decimal point. The decimal point is mandatory. It must not be before the first digit. Valid examples are “0.123”, “1.234”, “12.34”, “123.4” or “1234.”. Module name is a 20 character text for the identification of the channel. Only letters and numbers are allowed. Letters are converted into upper case. Module names with less than 20 characters are filled with spaces on the left side. The settings are transferred to the M72 immediately after entering. Valid entries are confirmed in the Status column by OK. Invalid entries are indicated as ERROR. Please note that settings transferred via the digital interface are not stored in the non-volatile memory of the M72 modules. This means that the M72 modules will be reset to the previous condition which was set via the front panel if the power supply is interrupted. If you want to keep your settings after switching off the device please click the button “Remanent Memory”. This will store all settings in the non-volatile memory of the M72 modules. The program also indicates type and version of the plugged in modules. Click Key Lock to disable the front panel keys of all modules. The button becomes yellow when the keys are locked. The key lock can be released by clicking the button again or by switching the power supply off and on. To save the entered settings to a file click Save Settings. Select a folder and enter a file name. The program will automatically append the extension “.xml”. You can reload the saved settings by clicking Load Settings. Select the “.xml” file and click OK. The loaded settings will be transferred to the M72 modules immediately. The program is based on LabView 2014. Metra provides the source code on demand.

Technical Data

Limited Warranty

Metra warrants for a period of 24 months that its products will be free from defects in material or workmanship and shall conform to the specifications current at the time of shipment.

The warranty period starts with the date of invoice. The customer must provide the dated bill of sale as evidence.  The warranty period ends after 24 months. Repairs do not extend the warranty period. This limited warranty covers only defects which arise as a result of normal use according to the instruction manual. Metra’s responsibility under this warranty does not apply to any improper or inadequate maintenance or modification and operation outside the product’s specifications. Shipment to Metra will be paid by the customer. The repaired or replaced product will be sent back at Metra’s expense.

Declaration of Conformity
According to EMC Directive 2014/30/EC and
UK Electromagnetic Compatibility Regulations 2016
Product: Charge/IEPE Conditioners
Type: M72A1/M72B1/M72B1/M72B3/M72R1/M72S1/M72R8/M72S8
It is hereby certified that the above-mentioned product complies with the demands pursuant to the following standards:

DIN / BS EN 61326-1: 2013
DIN / BS EN 61010-1: 2011
DIN 45669-1: 2010
The producer is responsible for this declaration
Metra Mess- und Frequenztechnik in Radebeul e.K.

Manfred Weber
Metra Mess- und Frequenztechnik in Radebeul e.K. Meißner Str. 58 – D-01445 Radebeul
Phone +49-351-836 2191
Fax +49-351-836 2940
Email: Info@MMF.de
Internet: www.MMF.de

References

• Schwingungsmesstechnik
• Schwingungsmesstechnik
• Product Literature

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