Related Manuals for ENDEVCO 2680 Series
Summary of Contents for ENDEVCO 2680 Series
- Page 1 MODEL 2680M1-M7/2680M12-M14/2680M61-67/2681M1-M7/2685M1-M7 AIRBORNE CHARGE AMPLIFIER INSTRUCTION MANUAL IM2680 Revision B Nov 1, 91...
- Page 2 San Juan Capistrano, Calif ornia, U.S.A. IM2680 Revision B Nov 1, 91...
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Page 3: Table Of Contents
ENDEVCO 2680 INSTRUCTION MANUAL TABLE OF CONTENTS SECTION 1: DESCRIPTION PAGE INTRODUCTION ADJUSTABLE GAIN OUTPUTS DC-TO-DC CONVERTER INPUT POWER OPTIONAL FILTERS ACCESSORIES APPLICATION SECTION 2: INSPECTION AND INSTALLATION INSPECTION INSTALLATION SECTION 3: PRE-OPERATION TEST INTRODUCTION EQUIPMENT REQUIRED VOLTAGE INSERTION TEST PROCEDURE... - Page 4 ENDEVCO 2680 INSTRUCTION MANUAL TABLE OF CONTENTS - continued APPENDIX B: GAIN ADJUSTMENT PAGE THEORETICAL GAIN ADJUSTMENT PRACTICAL GAIN ADJUSTMENT REMOVAL AND RESEALING GAIN-ACCESS SCREWS REMOVING ACCESS SCREWS SEALING ACCESS SCREWS LIST OF ILLUSTRATIONS VOLTAGE INSERTION TEST SETUP ALTERNATE CHARGE INSERTION TEST SETUP...
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Page 5: Introduction
DESCRIPTION INTRODUCTION The Endevco ® Model 2680 Series of Charge Amplifiers are Solid-State Airborne Devices designed for use with Piezoelectric Transducers. The Charge Amplifiers are epoxy-potted and hermetically sealed units containing a charge converter front end to receive the transducer signal, an optional filter to select the flat frequency response of the charge amplifier, a gain potentiometer to set the desired gain of the charge amplifier, and a voltage amplifier in the output. -
Page 6: Outputs
Connector Connector Accessories Conv. mA DC mA DC _ 2680 Microdot 51-49 Viking VR5/4AG15 Endevco Kit 21997 consisting of: 20-32 V < 20 < 25 10-32 Endevco P/N EP30 Mating Plug - Viking VP5/4CE6 28 V typ UNF-2A thread 5-Pin connector... -
Page 7: Dc-To-Dc Converter
ENDEVCO 2680 INSTRUCTION MANUAL ____________________________________________________________________________ _____________________________________________Output Characteristics______________________ DC Output Voltage Minimum Linear Output___________ Biased Input Adjustable Residual Unbiased Voltage Unbiased Voltage Current (10kΩ Model Charge Gain Range Noise Type Biased (+0.50/ (≥10kΩ >10kΩ >1MΩ Load at Min. M No. Limit (pC) mV/pC (mV rms) Output (±3%) -
Page 8: Optional Filters
APPLICATION The Model 2680 Series of Airborne Charge Amplifiers are ideally suited for inflight telemetry applications and other dynamic instrumentation systems using Transducers such as Piezoelectric Accelerometers, Microphones, Force Gages or Pressure Pickups. The small size, light weight,... -
Page 9: Section 2: Inspection And Installation
ENDEVCO 2680 INSTRUCTION MANUAL SECTION 2: INSPECTION AND INSTALLATION INSPECTION The Charge Amplifier is packed in a protective bag and packaged in a shipping carton containing shock-absorbent materials to prevent in-transit damage. However, upon receipt of the units, the customer should make an inspection to be certain that no damage has occurred during shipment. -
Page 10: Section 3: Pre-Operation Test
Digital voltmeter (DVM) to monitor Oscillator and Charge Amplifier Outputs in AC volts, or V rms. Accelerometer isolated mounting studs. Endevco Model 2980 Series isolated Mounting Stud is recommended. Stud is used to isolate Accelerometer from ground. Switch, SPDT (S1) -
Page 11: Voltage Insertion Test Procedure
ENDEVCO 2680 INSTRUCTION MANUAL VOLTAGE INSERTION TEST PROCEDURE Connect equipment as shown in Figure 3-1. Ensure Accelerometer is isolated from ground. As shown in Figure 3-1, the Accelerometer acts as a Passive Transducer when driven by the Oscillator. FIGURE 3-1: VOLTAGE INSERTION TEST SETUP Energize equipment and adjust power supply for +28 V dc output. -
Page 12: Alternate Test Method
ENDEVCO 2680 INSTRUCTION MANUAL Charge Amplifier Gain in mV/pC (see paragraph 4.2.) C in Input Capacitance in pF. Includes Accelerometer Capacitance (Cp) and Cable Capacitance (Cc) between Accel and T-Block Set switch S2 in Figure 3-1 test setup to OSC position. Readout devices should receive output of Oscillator. - Page 13 ENDEVCO 2680 INSTRUCTION MANUAL Connect equipment as shown in Figure 3-2. Energize equipment and adjust power supply for +28 V dc output. Allow 15 minutes for equipment to temperature stabilize. Establish an Output Voltage (E o ) for the Charge Amplifier. The Output Voltage should be less than the maximum Linear Output for the applicable Charge Amplifier.
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Page 14: Section 4: Operational Checkout Procedure
SECTION 4: OPERATIONAL CHECKOUT PROCEDURE USING THE CHARGE AMPLIFIER The 2680 series of Charge Amplifiers are designed to operate with Piezoelectric Accelerometers and other Transducers. In all cases the Transducer and Connecting Cable must form the equivalent of a capacitive input device. Total source capacitance for the input should not be more than 10,000 pF, or as specified on the Product Data Sheet, or Performance Specification. -
Page 15: Amplitude Linearity
ENDEVCO 2680 INSTRUCTION MANUAL FIGURE 4-1A: TYPICAL SYSTEM CONNECTIONS WITH CHARGE AMPLIFIER FIGURE 4-1B: TYPICAL SYSTEM CONNECTIONS WITH ISOTRON CONDITIONER AMPLITUDE LINEARITY Connect equipment per Figure 4-1. Ensure J2 pin assignment conforms to Charge Amplifier being tested. See Note in Figure 4-1. -
Page 16: Frequency Response
ENDEVCO 2680 INSTRUCTION MANUAL Non-linearity through this range should be less than 0.5% of best straight line. Refer to Product Data sheet, or paragraph 2.3.4 in Performance Specification for Amplitude Linearity limits of Charge Amplifier under test. FREQUENCY RESPONSE Connect equipment per Figure 4-1. -
Page 17: Appendix A: Theory Of Operation
As an example, suppose a system consisting of an Endevco Model 2680 Series Charge Amplifier (which has a 2.5 V pk, or 2500 mV pk full-scale output) and an Endevco Model 2272 Accelerometer is used as a system to measure ±50 g full scale pk. -
Page 18: Charge Converter
Sensitivity is not affected by capacitance connected external to the Transducer, no additional calculations are necessary. For example, the typical voltage sensitivity (E cal ) of the Endevco Model 2272 Accelerometer is 4.0 mV/g, typical capacitance is 2700 pF, and the Accelerometer is calibrated with 300 pF of external capacitance. -
Page 19: Gain Potentiometer
ENDEVCO 2680 INSTRUCTION MANUAL The transfer characteristic (conversion gain in mV/pC) of the Charge Converter depends primarily on the value of the Feedback Capacitor. When the Amplifier is operated within specification limits, the equation for conversion gain simplifies to the relationship:... - Page 20 ENDEVCO 2680 INSTRUCTION MANUAL A typical system (Accelerometer/Cable/Charge Amplifier) equivalent circuit is shown in Figure A-3. Note that Charge Gain is independent of Source Capacitance. In the circuit shown, C p is the Transducer Capacitance; C f is the total external shunt (cable) capacitance; and C p + C f is the total source capacitance for the Charge Amplifier.
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Page 21: Appendix B: Gain Adjustment Page
As an example, suppose a system consisting of an Endevco Model 2680 Series Charge Amplifier (which has a 2.5 V pk, or 2500 mV pk full-scale output) and an Endevco Model 2271 Accelerometer is used as a system to measure ±50 g full scale pk. -
Page 22: Practical Gain Adjustment
ENDEVCO 2680 INSTRUCTION MANUAL If a rms full-scale level is used for calibration, adequate gain margin should be included for the anticipated crest factor. PRACTICAL GAIN ADJUSTMENT To apply the Theoretical Gain Data in a practical situation, adjust the Gain of the Charge Amplifier with a known source capacitance and input voltage during calibration. -
Page 23: Removal And Resealing Gain-Access Screws
The instructions provided in paragraphs 4.3.2 and 4.3.3 are to be used when removing and resealing the access screw. Endevco recommends only new screws be installed in Charge Amplifiers. Access Screws can be procured from Endevco under part number 1103 (see Table B-1). -
Page 24: Removing Access Screws
ENDEVCO 2680 INSTRUCTION MANUAL TABLE B-1: EQUIPMENT REQUIRED REMOVING ACCESS SCREWS Preheat oven to +100°C. Place Charge Amplifier in preheated oven for a period of time sufficient for Charge Amplifier to stabilize at +100°C. Remove Charge Amplifier from oven. Insert Allen wrench (with isolated handle) in Access Screw to be removed (see appropriate Figure B-2 or B-3, and place soldering iron adjacent to Access Screw as shown in the diagram. - Page 25 ENDEVCO 2680 INSTRUCTION MANUAL FIGURE B-2: GAIN ADJUSTMENT FOR CHARGE AMPLIFIERS WITHOUT DC-TO-DC CONVERTERS FIGURE B-3. GAIN ADJUSTMENT FOR CHARGE AMPLIFIERS WITH DC-TO -DC CONVERTERS. IM2680 Page B-5...
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