Atec Endevco-2680M1, Endevco-2680M7 User Manual

Model 2680M1-M7

Variable

Gain

Amplifier

Optional

2 Pole

Butterworth

Low Pass

Filter

Charge

Convertor

Regulator

A+28 VDC

B

C

Unbiased

Output

Biased
Output

Signal &

Power

Ground

D

E

Case GND

Viking

VR5/4AG15

10-32 THD

Input

Connector

GAIN ADJUST

.154 (3.91) DIA 2 PL

.755 (19.18)
.745 (18.92)

1.000
(25.40)

.060
(1.52)

COUNTERBORED FOR
#6 CAP SCREW

.750
(19.05)

OUTPUT (VIKING

#VR5/4AG15 OR

EQUIVALENT)

PIN FUNCTIONS

A - +28 V DC
B - UNBIASED OUTPUT
C - BIASED OUTPUT
D - SIG & PWR GND
E - CASE GND

INPUT (MICRODOT #51-49 OR

EQUIVALENT) 10-32 UNF-2A THD

.200
(5.08)

.120
(3.05)

1.500
(38.10)

.120
(3.05)

1.000

(25.40)

1.255 (31.75)

1.245 (31.62)

D

C

B

A

E

STANDARD TOLERANCE

INCHES (MILLIMETERS)

.XX = +/- .02 (.X = +/- .5)

.XXX = +/- .010 (.XX = +/- .25)

Airborne charge amplifiers

Features Description

• For use with piezoelectric transducers

• Small, rugged, light weight

• Dual outputs, biased and unbiased

• Adjustable gain

• Optional low pass filter

The Endevco models 2680M1-XXX through 2680M7-XXX Charge
Amplifiers are designed for use with piezoelectric transducers
and are suitable for airborne applications. Hybrid microcircuit
construction results in small size, ruggedness and low power
consumption. The airborne charge amplifiers have an output
voltage proportional to the input charge. As a result, the ampli­fier sensitivity is not appreciably affected by the capacitance of
the input cable.

The use of modular construction techniques permits great
versatility in gain and filter choices. This unit has two outputs, a
biased output and an unbiased output. Both outputs are adjust­able with a common gain control. The M1 through M7 defines
the charge gain per Table 1.

The -XXX describes the upper cutoff frequency (-5% point) per
Table 2. 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.

"M" number Gain range Input pulse Residual noise

[mV/pC] [pC] [mV rms]

M1 0.1 to 1.0 50 000 1.5

M2 0.2 to 2.0 25 000 1.5

M3 0.5 to 5.0 10 000 1.5

M4 1.0 to 10.0 5000 1.5

M5 2.0 to 20.0 2500 1.5

M6 5.0 to 50.0 1000 1.5

M7 10.0 to 100 500 2.0

Table 1: Gain ranges

Dash No. Lower cutoff freq. [-5%] Upper cutoff freq. [-5%]

None 5 Hz 20 kHz (10 kHz for M7)

101 5 Hz 100 Hz

201 5 Hz 200 Hz

501 5 Hz 500 Hz

102 5 Hz 1 kHz

202 5 Hz 2 kHz

502 5 Hz 5 kHz

103 5 Hz 10 kHz

203 5 Hz 20 kHz (10 kHz for M7)

402 5 Hz 4 kHz

250 5 Hz 25 Hz

Table 2: Frequency response

APPLIES TO CALIFORNIA FACILITY

Model 2680M1-M7
Airborne charge amplifiers

Specifications

The following performance specifications conform to ISA-RP-37.2 (1964) and are typical values, referenced at +75˚F (+24˚C) and 100 Hz,

unless otherwise noted. Calibration data, traceable to National Institute of Standards and Technology (NIST), is supplied.

Inputs

Type Piezoelectric single-ended with one side connected to signal ground
Source resistance 25 MΩ minimum
Source capacitance 10 000 pF max
Overload recovery A half sine pulse of 1ms duration and with an amplitude as specified in Table 1 (or less) will cause no

spurious effects at the amplifier output other than clipping.

Outputs

Type Both biased and unbiased outputs are single-ended with one side connected to circuit ground.
Load impedance The parallel combination of both outputs load resistors shall be 10 kΩ or greater to meet all specifications.
Output impedance Biased output 50 Ω max, direct coupled

Unbiased output 50 Ω max, in series with at least 16 μF
DC output bias voltage Biased output 2.50 V ±3% with load resistances of 10 kΩ minimum

Unbiased output 0.00 V +0.050 V / -0.00 V

Linear output voltage Biased output 4.65 V pk-pk minimum with 10 kΩ load
Unbiased output 4.65 V pk-pk minimum with 1 MΩ load

4.25 V pk-pk minimum with 10 kΩ load

Limited output voltage (biased output) 0.00 V +0.075/-0.000 V and 5.30 V +0.00/-0.30 V
Limited output current (both output) 0.465 mA pk-pk minimum with 10 kΩ load

Transfer characteristics

Gain range Adjustable as specified in Table 1
Gain stability 0.05% maximum change per 1000 pF change in source capacitance at the input

Gain stability with supply voltage 0.25% maximum with changes in supply voltage over the specified limits

Frequency response The gain at the upper and lower cutoff frequencies is 5% lower than the gain at 20 Hz. See Table 2.
Amplitude linearity ±0.5% of reading from best fit straight line approximation
Residual noise 0.01 pC rms + 0.01 pC rms per 1000 pF RTI or noise RTO as specified in Table 1 whichever is greater,

when measured over a bandwidth of 3 Hz to 20 kHz

Shock and vibration sensitivity 0.01 pC/g maximum RTI

Environmental

Temperature Operating -67°F to 212°F (-55°C to 100°C)

Storage -99°F to 257°F (-73°C to 125°C)

Humidity 100% R.H. when sealing screw is soldered. Meets MIL-STD-810D, Method 507.2, Procedure III
Altitude No effect when sealing screw is soldered.
Vibration 120 mils D.A. 5 Hz to 55 Hz

20 g 55 Hz to 2000 Hz

Shock 100 g 6.5 millisecond sawtooth
EMC capability The unit meets 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 20 to 32 VDC (28 VDC nominal)
Current 20 mA maximum for unfiltered units, 25 mA maximum for filtered units
Polarity protection Not damaged by a polarity reversal of the 28 V supply
Case isolation Case and signal grounds isolated from each other by 50 M½ or greater at 50 VDC

Physical characteristics

Dimensions 1.00” l x 1.00” w x 0.75” h (25.4 mm x 25.4 mm x 19.1 mm) exclusive of mounting flange and connectors
Mounting Unit mounts with two 6-32 screws
Case material Aluminum with electroless nickel plate finish
Weight 1.2 oz (34 gm) maximum
Connectors Input 10-32 coaxial

Output Viking VR5/4AG15. Pin A is the 28 VDC, Pin B unbiased output, Pin C biased output,
Pin D power and signal ground, Pin E case ground

Accessories

Instruction manual
21997 Accessory Kit includes:
EP38 Mating plug Viking #VP5/4CE6
EP35 Hood Viking #VS4/16C5
EP31 Potting sleeve Viking #VS4/16C9

Continued product improvement necessitates that Endevco reserve the right to modify these specifications without notice. Endevco maintains a program of constant 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.

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