Encore 635-002 User Manual

MANUAL

MODEL 635-002

STRAIN GAGE AMPLIFIER

INDEX

2...................DESCRIPTION

3...................I. SPECIFICATIONS: AMPLIFIER MODULE

5...................II. SPECIFICATIONS: RACK ADAPTER ASSEMBLY

6...................III. SPECIFICATIONS: POWER SUPPLY

7...................PCB JUMPER ASSIGNMENTS

8...................BRIDGE MODES, FIGURE 1

9...................CIRCUIT DESCRIPTION

10-13............PIN-OUT TABLES

14.................SET-UP PROCEDURE

16.................ACCEPTANCE TEST PROCEDURE

17.................ACCEPTANCE TEST DATA SHEET

19.................SCHEMATIC: AMPLIFIER MODULE D13555

20.................SCHEMATIC: POWER SUPPLY C13597

21.................FRONT RACK: ASSEMBLY 4007-137

22.................REAR RACK: ASSEMBLY 4007-137

Reviewed 3.24.03 mbz

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MODEL 635

DESCRIPTION

FUNCTION: The Model 635 Strain Gage amplifier is used to condition strain gage signals and to provide precise, low­noise excitation voltages to the strain gage(s).

CONSTRUCTION: The amplifier uses modular construction. Seven modules can be accommodated in a rack adapter,

Encore Model 4007-137. The rack also accommodates a Model 843 power supply module. This module provides
unregulated +,-24VDC for the amplifier circuitry, plus seven isolated +,-24VDC outputs for the bridge excitation circuits.

FEATURES: A number of parameters and operating modes are selectable with the front panel controls. Automatic bridge
balance with battery backup is standard. Selectable parameters include cal-select resistors, gain, frequency response,
internal bridge-completion components, and bridge excitation voltage. Selectable modes include AC/DC coupling, internal
DC CAL, external CAL, and ZERO. The ZERO position allows the operator to null the amplifier and to evaluate noise
attributable to the amplifier. An ON/OFF switch for bridge excitation enables the operator to evaluate noise pick-up
attributable to gauge installation (Switch Off) and signal (Switch On).

A mode switch is provided to select the bridge configuration, including 1/4 static, 1/2 static, 1/4 dynamic, and full bridge.
An additional position selects the EMF input mode for operation of the amplifier as a high-performance, general purpose
differential amplifier.

Each module front panel provides two LED indications, one for output signal limit and the other for auto-balance status.
The balance LED will light during a balance cycle, and will remain lit if an unbalanceable condition exists. It will also light
on power-up if the back-up battery is weak.

The auto-balance can be initiated for all channels with a push-button on the power supply module or with a zero-level on a
BNC located on the rear panel of the rack adapter. Also, modules can be individually auto-balanced with a recessed front
panel push-button.

Another major feature of the amplifier is that it provides two channels. One is a MAIN AC/DC channel whose parameters
are controlled from the module front panel. The other channel is a DC auxiliary channel with fixed parameters, although
the gain is jumper-selected from 1 to 500. The main channel is generally used for low-level dynamic strain measurement,
while the auxiliary channel monitors the static strain.

Detailed specifications describing the module, rack assembly and power supply are included in this manual. Also included
are outline drawings and schematics.

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MODEL 635

I. SPECIFICATIONS: AMPLIFIER MODULE

MECHANICAL: The amplifier plug-in module is 7"H x 2"W x 12"D and weighs 16 oz.

BRIDGE EXCITATION: Front panel adjustable, +1.0 to +15VDC with ON/OFF switch. A separate transformer-

isolated, unregulated + ,-24VDC power source is provided to each module.

BRIDGE CONFIGURATION: Front panel switch selectable for 1/4 STATIC, 1/2 STATIC, 1/4 DYNAMIC, FULL and
EMF as follows:

1/4 STAT POSITION: Single active gage in a bridge configuration.

1/2 STAT POSITION: Two active gage in a bridge configuration.

1/4 DYN POSITION: Single gage in series with CV excitation source. An internal 400 ohm resistor is in series with

the gage to induce gage-voltage variations with strain.

FULL POSITION: Four externally connected active gages in bridge configuration.

EMF POSITION: For GENERAL PURPOSE differential amplifier. Input signal is applied to +S and -S terminals

of the bridge/amplifier connector.

BRIDGE COMPLETION: Front panel toggle selects either 120 ohm or 350 ohm completion resistors in the 1/4 and 1/2
STATIC modes.

AUTO-BALANCE: The AUTO-BALANCE function is remotely activated for all modules simultaneously with a zero­level on a rear panel BNC or a push-button on the power supply module. Individual modules can be activated with a front
panel push-button.

Resolution: +, -2.1 mV/V of excitation at G=1000. (RTO)

A front panel LED indicates an unbalanceable condition.

AMPLIFIER CONFIGURATION: The input signal is applied to two parallel amplifier channels, as follows:

MAIN AC/DC CHANNEL #1: A front panel adjustable amplifier.

DC ONLY CHANNEL #2: A fixed gain of 100, DC coupled, with a fixed frequency response of 11Hz (-3dB). Output is

rated to +, -10V at 10mA. Gains of 1, 100, 200 or 500 can be selected with a PCB jumper (J6), within a 1% tolerance.

MODE: Front panel mode switch selects either EXTERNAL CAL, AC coupled, DC coupled, DC CAL, or ZERO, as
follows:

EXTERNAL CAL: 0 to +,-2V is connected to all of the amplifier inputs through EXT.CAL BNC at rear of rack

assembly.

AC: The input circuit is AC coupled down to 12Hz (-3dB).

Continued on next page

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DC: The input circuit is DC coupled.

DC CAL: A front-panel-selected internal calibration resistor is connected from -P to +S or -P to -S

(Jumper Selectable).Values are 11.88K, 19.88K, 49.00K and 99.00K.

ZERO: Used with front panel trimpot to null the amplifier with zero-input signal.

INPUT SIGNAL: The sum of the DC and AC signals should not exceed +,-10Vdivided by the gain setting.

GAIN: Front panel gain switch selects fixed gains from 1 to 5000 +,-2% in log steps. A front panel gain vernier adjusts

between fixed gains.

FREQUENCY RESPONSE: Front panel switch selects 3-pole Butterworth low pass filter with nominal -3dB points at
200, 500, 5000, 16000 and 32000Hz. Frequency response in the filter "OUT" position is 100KHz. The frequency response
of the DC channel is 11Hz nominal.

COMMON MODE VOLTAGE: +,-10V Max.

CMRR: 100dB, DC to 70Hz, DC coupled.

80dB, 70Hz, AC coupled.
80dB, 1KHz, DC coupled.

MONITOR OUTPUT: +,-10V Max., 0 to 100 mA PK.

TAPE OUTPUT: +,-10V Max., 2K ohm minimum load.

NOISE: 2.5 microvolts RMS, RTI at G=1000.

DRIFT: Within +,-10 microvolts, RTI at G=1000 for 24 hrs after a one hour warm up.

LIMIT INDICATOR: LED lights whenever output signal exceeds 1.0V RMS (factory preset).

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II. SPECIFICATIONS: MODEL 4007-137 RACK ADAPTER ASSEMBLY

RACK CONFIGURATION: The rack adapter assembly is 19"W x 16 1/2"D x 7"H. It accommodates one Model 843
power supply module and seven Model 635 amplifier modules.

REAR PANEL CONNECTORS: There are five types of termination on the rear of the rack, as follows:

TAPE OUTPUT: One insulated BNC per amplifier channel. These are low power, buffered outputs for tape

recorders, oscilloscopes and other high impedance instrumentation.

MONITOR OUTPUT: One 18-pin bulkhead connector per rack for the high- power output circuit of each
amplifier module. These outputs are used for driving low impedance loads with high shunt capacitance cables, ie: 50
ohms, .056uf.

DC OUTPUTS: Seven 3-pin bulkhead connectors per rack connect to the output of the fixed DC channels.

BRIDGE/AMPLIFIER INPUT: One 6-pin bulkhead connector per amplifier channel for interfacing the strain gages to

their respective amplifiers.

CAL: One insulated BNC per rack, accepts external calibration signal.

AUTO-BAL: One insulated BNC per rack accepts external auto-balance command.

REMOTE: One insulated BNC per rack, through which a circuit closure, either switched or from a computer,

disconnects the normal inputs of each amplifier module and replaces it with the "EXT. CAL" signal.

LINE CORD RECEPTACLE: Accepts 3-wire cord to plug into 115VAC, +,-10%,50/60Hz power line.

III. SPECIFICATIONS

MODEL 843 POWER SUPPLY MODULE

DESCRIPTION: Both the input and output connections are made with a PC edge connector at the rear of the module.
A fully shielded, toroidal power transformer allows the PS module to operate adjacent to a high-gain amplifier module
without inducing 60Hz pick-up noise. Rectifiers and electrolytic capacitors complete the circuit which provides the +,­24VDC (nominal), unregulated output voltages. These voltages are routed through the PC connector to each amplifier
module, where they are regulated as needed.

MECHANICAL: The power supply module is 7"H x 2.8"W x 12"D and weighs 4.5 lbs.

ELECTRICAL:

INPUT: 115V +,-10%, 50/60 Hz @ 0.8A Max.

OUTPUT: Eight unregulated, transformer isolated DC outputs, as follows:

1@ +24VDC at nominal line and full load; 1.2A MAX.

1@ -24VDC at nominal line and full load; 0.6A MAX.

7@ +24VDC @ 0.08A@ (.56A total)

Ripple: 1.5V PK/PK Max. per output

CONTROLS:

Power "ON" switch and Indicator lamp.

Front Panel 1A, SLO-BLO line fuse.

Front Panel toggle switch for grounding power supply common.

Front panel push-button to actuate AUTOBALANCE.