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Models 2680M1/2685M1
Airborne Amplifier
Instruction Manual # (TBD)
Piezoelectric accelerometers
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Piezoresistive accelerometers
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IEPE accelerometers
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Variable capacitance accelerometers
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Piezoresistive pressure sensors
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Piezoelectric pressure sensors
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High intensity microphones
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Inertial sensors
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Signal conditioners and supportive instrumentation
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Cable assemblies
ENDEVCO
www.endevco.com
Tel: +1 (866) ENDEVCO [+1 (866) 363-3826]
IM 2680/5 083119
1
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Table of Contents
Related Manuals for ENDEVCO 2680M1
Summary of Contents for ENDEVCO 2680M1
- Page 1 Instruction Manual # (TBD) Piezoelectric accelerometers Piezoresistive accelerometers IEPE accelerometers Variable capacitance accelerometers Piezoresistive pressure sensors Piezoelectric pressure sensors High intensity microphones Inertial sensors Signal conditioners and supportive instrumentation Cable assemblies ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119...
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Page 2: Table Of Contents
2685 quick test 2680 Testing without the sensor Final electrical and mechanical installation Maintenance and calibration Returning the unit Appendix A: Cable installation Recommendations Appendix B: Why a calibration capacitor? ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119... -
Page 3: Products Covered
INSTRUCTION MANUAL PRODUCTS COVERED This manual covers the model 2680M1 charge amplifier and the 2685M1 IEPE (ISOTRON®) signal conditioner and applicable accessories. The full model number is printed on the label located on the top of the unit. The below tables describe the numbering system and applicable parameters. - Page 4 3 Hz ±2Hz 20 kHz* 40 kHz 80 kHz “dash” number for the -150 0.7 Hz 3 Hz ±2Hz 15 Hz 30 Hz 60 Hz 2685 only. *Limit + 5%, -10% ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119...
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Page 5: Product Description
PRODUCT DESCRIPTION The Endevco Model 2680 and 2685 Series of Airborne Amplifiers are solid-state airborne devices designed for use with piezoelectric and IEPE transducers. The 2680 and 2685 are essentially identical with the exception of the front-end (see figures 1 and 2). The airborne amplifiers are potted with polyurethane foam and sealed. -
Page 6: Initial Inspection
7.1 of this manual. It is recommended that an applications engineer be contacted prior to returning the unit since many problems can be resolved via telephone of email. ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119... -
Page 7: Installation
The 2680 airborne amplifier is configured to operate with charge-mode transducers thus the input cable must be low-noise treated. Cable assemblies such as the Endevco 3090C or the premium 3090DV are recommended. The connector on the airborne amplifier is a 10-32 type. -
Page 8: 2685 Input Cable
The 2685 is designed to operate with IEPE (ISOTRON) accelerometers, thus low- noise treated cables are unnecessary. Recommended cable assemblies are the Endevco Teflon C-001-AC-001-X or the Endevco silicone C-001-AD-001-X. The connector on the airborne amplifier is a 10-32 type. -
Page 9: Biased Output
4. Remove the access screw using a 5/64” hex wrench with an insulated handle. Figure 4 illustrates removal, re-installation and solder sealing of the gain adjustment potentiometer A 200-watt soldering iron with a narrow tip is recommended ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119... -
Page 10: Unsoldering The Access Screw
A 1/16” (1.6 mm) flat blade screwdriver is recommended for adjusting the potentiometer. Airborne amplifiers shipped as a component of an Endevco system consisting of an airborne amplifier with a cable assembly and either an accelerometer or microphone; normally have the gain factory-set to a specific level, and the gain-access screw solder-sealed to the case of the airborne amplifier. -
Page 11: 6 How To Calculate Gain And Output Level
For example, suppose a system consisting of a charge-mode piezoelectric accelerometer is used to measure ± 50g peak, full scale with a 2680 amplifier (which has a 2500 mV full-scale output). ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119... -
Page 12: 7 2685 Considerations
To determine the maximum negative voltage: – Fs = Eb – 2 Fs = Full scale output voltage (peak) Where: Es = DC compliance voltage Eb = Bias voltage (from accelerometer calibration certificate ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119... -
Page 13: 8 What To Look For
In some cases the time domain display on the oscilloscope can appear as clean as figure 6A, but there may be distortion present that will only be detectable in the frequency domain or on a harmonic distortion analyzer. ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119... - Page 14 Figure 6D is an example of the presence of clipping as seen in the time domain. In this case further analysis using the FFT mode is unnecessary since the problem is obvious. (Figure 6D) Frequency ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119...
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Page 15: 0 Environmental Considerations
High temperature accelerometers usually specify resistance at room temperature and at the maximum temperature. The specified source resistance of the 2680 is 3 M Ω, minimum. ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119... -
Page 16: 0 Performance Testing
The most efficient way to test the performance is described in section 6.1. If these instruments are unavailable, section 6.2 suggests methods where standard laboratory instrumentation can be used to effectively perform the tests. See the appropriate Endevco technical paper for further tests, if required Preferred method, 2680 and 2685... - Page 17 Set the reference shaker frequency to 100Hz. Observe a 100 Hz undistorted sine wave on the oscilloscope. If the oscilloscope is DC coupled a DC bias of 2.50 volts (±3%)should also be observed ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119...
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Page 18: Accelerometer Simulator Method
An accelerometer simulator is also a good source for testing the performance of the 2680 or 2685. In this instance, the accelerometer is absent from the circuit. The Endevco model 4830B (figure 10) is an example of an accelerometer simulator. -
Page 19: 2680 Quick Test
Figure 11: The left side of the trace shows the initial strike followed by the “ring” from the accelerometers resonance. Other patterns are possible from a “good” system. ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119... -
Page 20: 14 2685 Quick Test
Install the accelerometer cable in such a way that the DC voltage can be measured. This is best accomplished using a pair of 10- 32 to BNC cables (Endevco 3061) joined by a BNC “T” connector (Amphenol 112461, or equiv.) per figure 5. -
Page 21: 2 2680 Testing Without The Sensor
2680 Testing without the sensor Testing with high accuracy is possible using common laboratory instruments and an Endevco model 2947C Calibration Capacitor. The 2947C is simply a stable, well-shielded 1000pF capacitor that is placed between the signal generator and the 2680 charge amplifier. Its purpose is to convert the signal generators output voltage to a charge (pF) signal. -
Page 22: 3 Final Electrical And Mechanical Installation
8 in-lb (0.9 Nm) and the material of the mounting surface. The accelerometer input cable should be installed with a mounting torque of 1.5 in-lbs. (0.169 Nm), finger tight. ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119... - Page 23 Figure 15A: Outline drawing of the 2680 Charge amplifier. Figure 15B: Outline drawing for the 2685 IEPE (ISOTRON) amplifier. ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119...
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Page 24: Maintenance And Calibration
Include a description of the problem encountered and the unit serial number and your contact information. Outside USA: Contact your local representative or distributor and follow their instructions. ENDEVCO www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826] IM 2680/5 083119... -
Page 25: Appendix A: Cable Installation Recommendations
APPENDIX A: CABLE INSTALLATION RECOMMENDATIONS The following recommendations are provided to help the users of Endevco cables and assemblies. When attaching a coaxial cable assembly to a transducer or the amplifier, always turn the connector nut onto the transducer. Turning... -
Page 26: Appendix B: Why A Calibration Capacitor
100 Hz, thus this frequency is the recommended input used for this test. The uncertainty will be that of the signal source and the capacitor. The Endevco 2947C has an uncertainty of ±1%. Adequate shielding is required for optimum accuracy; the amplifier, being a high impedance devic sensitive to ambient noise.
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