Charge Amplifier
Model 2680M14
• For Use with Piezoelectric
Transducers
• Small, Rugged, Light Weight
• Dual Unbiased Outputs
• Adjustable Gain
• Optional Low-Pass Filter
Not actual size
ENDEVCO
MODEL
2680M14
DESCRIPTION
The ENDEVCO
®
Model 2680M14-XXX
Series Charge Amplifier is designed for use with
piezoelectric transducers and is suitable for air-
borne applications. Hybrid micro-circuits
construction results in small size, ruggedness and
low power consumption. The unit is a charge
amplifier; that is, it has an output voltage
proportional to the charge at the input. As a
result, the amplifier sensitivity is not appreciably
affected by the capacitance of the input cable.
This unit has two outputs, an unbiased, low gain
output with a gain range of 1-10 mV/pC, and
an unbiased high gain output with a gain range
of 10-100 mV/pC. Both outputs are adjustable
with a common gain control.
The -XXX describes the upper cutoff frequency
(-5% point) per Table 1. For example, a -101 has
a low pass filter which is flat up to 100 Hz, a -502
has a low pass filter which is flat up to 5000 Hz.
Dash No.
None
None
101
201
501
102
202
502
103
203
203
Gain Range
[mV/pC]
1-10
10-100
Both outputs
Both outputs
Both outputs
Both outputs
Both outputs
Both outputs
Both outputs
1-10
10-100
Lower Cutoff
Frequency [ -5%]
5 Hz
5 Hz
5 Hz
5 Hz
5 Hz
5 Hz
5 Hz
5 Hz
5 Hz
5 Hz
5 Hz
Upper Cutoff
Frequency [-5%]
20 kHz
10 kHz
100 Hz
200 Hz
500 Hz
1 kHz
2 kHz
5 kHz
10 kHz
20 kHz
10 kHz
TABLE 1: FREQUENCY RESPONSE
PIN FUNCTION
A - +28 V DC
B - 1-10 UNBIASED OUTPUT
C - 1-100 UNBIASED OUTPUT
D - SIG & PWR GND
E - CASE GND
GAIN ADJUST
.154 (3.91) DIA 2 PL
COUNTERBORED FOR
#6 CAP SCREW
Regulator
10-32 THD
Input
Connector
Charge
Convertor
A
+28 VDC
.755 (19.18)
.745 (18.92)
1.000
(25.40)
Optional
2 Pole
Butterworth
Low Pass
Filter
Variable
Gain
Amplifier
X10
Unbiased
Output
1-10 mV/pC
B
C
Unbiased
Output
10-100 mV/pC
Signal &
Power
Ground
Case GND
.120
(3.05)
1.455 (36.95)
1.445 (36.70)
1.700
(43.18)
1.200
(30.48)
.120
(3.05)
D
OUTPUT (VIKING
#VR5/4AG15 OR
EQUIVALENT)
C
B
D
E
A
E
Viking
VR5/4AG15
.200
(5.08)
.060
(1.52)
.750
(19.05)
INPUT (MICRODOT #51-49 OR
EQUIVALENT) 10-32 UNF-2A THD
STANDARD TOLERANCE
INCHES
(MILLIMETERS)
.XX = +/- .02 (.X = +/- .5)
.XXX = +/- .010 (.XX = +/- .25)
APPLIES TO CALIFORNIA FACILITY
ENDEVCO
Charge Amplifier
SPECIFICATIONS
INPUTS
TYPE
SOURCE RESISTANCE
SOURCE CAPACITANCE
OVERLOAD RECOVERY
Piezoelectric single-ended with one side connected to signal ground
25 MΩ minimum
10 000 pF maximum
A half sine pulse of 1 ms duration with an amplitude of 5000 pC or less will cause no
spurious effects at the amplifier output other than clipping.
MODEL
2680M14
OUTPUTS (The following characteristics apply to both outputs)
TYPE
Single-ended with one side connected to circuit ground
OUTPUT IMPEDANCE
50
Ω
maximum, in series with at least 16 µF
DC OUTPUT BIAS VOLTAGE
0.00 V +.050 V/-0.00 V
LINEAR OUTPUT VOLTAGE
5.00 V pk-pk minimum with 10 kΩ load resistance
LIMITED OUTPUT VOLTAGE
6.00 V pk-pk
LINEAR OUTPUT CURRENT
0.500 mA pk-pk minimum with 10 kΩ load
TRANSFER CHARACTERISTICS
GAIN RANGE
Gain Ratio
GAIN STABILITY
Gain Stability with Supply Voltage
FREQUENCY RESPONSE
AMPLITUDE LINEARITY
RESIDUAL NOISE
SHOCK AND VIBRATION SENSITIVITY
ENVIRONMENTAL
TEMPERATURE
HUMIDITY
ALTITUDE
VIBRATION
SHOCK
E.M.C. CAPABILITY
Low Gain Output
1 to 10 mV/pC
High Gain Output
10 to 100 mV/pC
10:1, ±3% between high and low gain outputs
0.05% maximum change per 1000 pF change in source capacitance at the input
0.25% maximum with changes in supply voltage over the specified limits
The gain at the lower and upper cutoff frequency is 5% lower than the gain at
20 Hz. See Table 1.
±0.5% of reading from best fit straight line approximation
0.01 pC rms +0.01 pC rms per 1000 pF RTI or 1.5 mV rms RTO low gain and
15 mV rms RTO high gain, whichever is greater, when measured over a bandwidth
of 3 Hz to 20 kHz
0.01 pC/g.maximum RTI
Operating -67°F to 212°F (-55°C to 100°C)
Storage
-99°F to 257°F (-73°C to 125°C)
100% R.H. when sealing screw is soldered. Meets MIL-STD-810D, Method 507.2,
Procedure III.
No effect when sealing screw is soldered.
120 mils D.A.
5 Hz to 55 Hz
20 g
55 Hz to 2000 Hz
100 g
6.5 millisecond sawtooth
The unit will meet the requirements of the following specifications:
MIL-STD-826, CLASS Am; MIL-I-6181D;
MSFC-SPEC-279, CLASS 1; AF/BSD EXHIBIT 62-87.
POWER
VOLTAGE
CURRENT
POLARITY PROTECTION
CASE ISOLATION
PHYSICAL
DIMENSIONS
MOUNTING
CASE MATERIAL
WEIGHT
CONNECTORS
20 to 32 VDC (28 VDC nominal)
30 mA maximum for unfiltered units, 35 mA maximum for filtered units
Not damaged by a polarity reversal of the 28 V supply
Case and signal grounds isolated from each other by 50 MΩ or greater at 50 VDC
1.20" l x 1.00" w x 0.75" h (30.5 mm x 25.4 mm x 19.1 mm ) exclusive of mounting
flange and connectors
Unit mounts with two 6-32 screws
Aluminum with electroless nickel plate finish
1.5 oz (42.5 gm) maximum
Input
10-32 coaxial
Output
Viking VR5/4AG15. Pin A is the 28 VDC, Pin B unbiased
low gain output, pin C unbiased high gain output, pin D
power and signal ground, pin E case ground
ACCESSORIES
Instruction Manual
21997
EP38
EP35
EP31
Accessory Kit Includes:
Mating Plug
Viking #VP5/4CE6
Hood
VIking #VS4/16C5
Potting Sleeve
Viking #VS4/16C9
Notes
Maintain high levels of precision and accuracy using Endevco's factory calibration services. Call Endevco’s inside sales force at
800-982-6732 for recommended intervals, pricing and turn-around time for these services as well as for quotations on our standard products.
Continued product improvement necessitates that Endevco reserve the right to modify these specifications without notice. Endevco maintains a program of con-
stant surveillance over all products to ensure a high level of reliability. This program includes attention to reliability factors during product design, the support of
stringent Quality Control requirements, and compulsory corrective action procedures. These measures, together with conservative specifications have made the
name Endevco synonymous with reliability.
ENDEVCO CORPORATION, 30700 RANCHO VIEJO ROAD, SAN JUAN CAPISTRANO, CA 92675 USA (800) 982-6732 (949) 493-8181 fax (949) 661-7231
www.endevco.com
Email:applications@endevco.com
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