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Summary of Contents for MMF M68 Series
- Page 1 Instruction Manual Charge Amplifiers M68 Series 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...
- Page 2 The latest version of this document can be downloaded from: http://www.mmf.de/product_literature.htm © Manfred Weber Metra Mess- und Frequenztechnik in Radebeul e.K. Aug. 10 #162...
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Page 3: Table Of Contents
Contents 1.Application..........................5 2.Function and Operation......................5 3.Power Supply..........................6 3.1.Grounding Concept......................6 3.2.External Supply .........................6 3.3.Battery Operation (M68D1)....................7 4.Inputs............................7 4.1.Charge Input ........................7 4.2.IEPE Input .........................7 4.2.1.Switching Off the IEPE Supply .................9 5.Avoiding Ground Loops......................9 6.Amplifier ..........................10 7.Level Indicators........................10 8.Low Pass Filter ........................11 9.High Pass Filter........................12 10.Integrators..........................12 11.Rack Cases for Model... - Page 4 Figure 1: Front view of Model M68D1 with control elements...
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Page 5: Application
1. Application The Signal Conditioners of M68 series 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 or microphones. By means of the M68 the sensor signal can be best possibly adapted to the existing measuring equipment or PC-based data acquisition systems. -
Page 6: Power Supply
bandwidth down to 0.1 Hz comes into effect. The filters are followed by the second amplifier stage. The divided gain before and after filtering provides sufficient dynamic range, even for si- gnal components outside the filter range. At the same time a high signal-to-noise ratio is achie - ved. -
Page 7: Battery Operation (M68D1)
The instruments are protected against false polarization and short-time excess voltage up to 60 V. All models of M68 series have an LED “BAT O.K.” indicating sufficient supply voltage. It lights up green, as long as the voltage is above 5 V. It works for battery operation as well as for external power supply (M68D1). - Page 8 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 line. Figure 4 shows the circuit diagram. To separate the low impedance sensor signal from the power supply, the integrated circuit is supplied with constant current.
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Page 9: Switching Off The Iepe Supply
positive overload Max. output voltage = supply voltage of 24 V constant current source Sensor bias voltage 5 .. 14 V (see data sheet) Min. output voltage = 0.5..1 V saturation voltage (see data sheet) negative overload Figure 5: Dynamic range of IEPE compatible transducers 4.2.1. -
Page 10: Amplifier
If you have the choice to use differential inputs, which can be found on many data acquisition boards, you should preferably use them. 6. Amplifier The instruments of M68 Series have the following measuring ranges: Charge mode: 0.1 / 1 / 10 / 100 / 1000 mV/pC... -
Page 11: Low Pass Filter
1/10 the sampling frequency. The instruments of M68 series have 6 internal low pass filters. The scale at the positions of the filter switch “LOW PASS” is shows the 3 dB limiting frequencies in kHz. The following table... -
Page 12: High Pass Filter
9. High Pass Filter The M68 signal conditioners have a high pass filter with a lower limiting frequency of 3 Hz (- 3 dB). By means of this filter low frequency noise can be removed. Low frequency noise may occur, for example, by the influence of temperature transients to piezoelectric compression type accelerometers. - Page 13 Vibration acceleration a (without integration): G⋅B (a in m/s²; u in mV; G in mV/mV; B in mV/ms Vibration velocity v (single integration): ⋅10 G⋅B (v in mm/s; u in mV; G in mV/mV; B in mV/ms Vibration displacement d (double integration): ⋅100 G⋅B (d in µm;...
- Page 14 Max. modulation Modulation limits 1000 Figure 8: Frequency response of the integrators 180° 90° -90° -180° 1000 Figure 9: Pase response of the integrators In some cases signal components with high frequency and magnitude may overload the ampli- fier although no overload can be detected at the M68 output. The overload LED remains dark. This can occur due to the attenuation of higher frequencies by the integrator (compare Figure 8).
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Page 15: Rack Cases For Model M68R1
11. Rack Cases for Model M68R1 For the 19” unit M68R1 the following rack mounting cases are available: Model Channels Built-in power supply M68B6 M68B12 Figure 10: Front view of rack case M68B12 Figure 11: Rear view of rack case Model M68B6 The rack cases Models M68B6 and M68B12 supply the plugged-in modules via a backplane. -
Page 16: Technical Data
The fuse holder of the rack cases M68B6 and M68B12 with mains power supply is located insi- de the mains socket at the rear. It can be pulled out using a screw driver. The fuse facing to the back of the drawer is a spare fuse. The rear one is the mains fuse. Important: Unplug the device from the mains voltage before replacing the fuse. - Page 17 5 .. 15 VDC External supply < 300 mA (M68D1, M68R1) < 1 A (M68D3) connector to DIN 45323 (M68D1 / M68D3) 4 pin frame connector (M68R1) 4 x “AA” size (LR6) Battery supply (only M68D1) > 10 h lifetime with alkaline cells Wide range input 85 ..
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Page 18: Appendix: Limited Warranty
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. -
Page 19: Declaration Of Conformity
Declaration of Conformity Products: Charge Amplifiers Models: M68D1, M68D3, M68R1, M68B6, M68B12 It is hereby certified that the above mentioned products comply with the demands pursuant to the following standards: • EN 50081-1 • EN 50082-1 • EN 61000-3 • EN 60950 Responsible for this declaration is the producer Metra Mess- und Frequenztechnik...
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