User guide

ManualsBrandsCooper Instruments & Systems ManualsReceivers and AmplifiersDCM 460 Voltage Bridge Amplifier

CF 28 1 4/2001

DCM 460 VOLTAGE BRIDGE AMPLIFIER

Description

The DCM 460 Bridgesensor is a self-contained, AC powered, signal conditioning module for bridge type

instrumentation. It contains a precision differential instrumentation amplifier with filtered output and a highly

regulated, low noise, adjustable output bridge excitation source. The unit is completely encapsulated for use in

rugged environments. The output filter cutoff frequency is 2000Hz and may be lowered by adding two external

capacitors.

Features

• 2 kHz Frequency Response

• Rugged, Compact And Fully Encapsulated

• Complete System-just Add AC Power

• Ready To Use With Screwdriver Wiring

• Stable and Accurate

Applications

• Weighing With Load Cells

• Long Term Structural Monitoring

• Process Control Pressure Transducers

• Temperature Controls Using Thermocouples

• Strain Measurements

Figure 1. Simplified Block Diagram

Summary of content (6 pages)

PAGE 1
DCM 460 VOLTAGE BRIDGE AMPLIFIER Description The DCM 460 Bridgesensor is a self-contained, AC powered, signal conditioning module for bridge type instrumentation. It contains a precision differential instrumentation amplifier with filtered output and a highly regulated, low noise, adjustable output bridge excitation source. The unit is completely encapsulated for use in rugged environments. The output filter cutoff frequency is 2000Hz and may be lowered by adding two external capacitors.
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Specifications (Typical @ 25°C unless noted) Amplifier Gain Range Gain Temperature Coefficient Drift (RTI) Input Bias Current Input Impedance Differential Common Mode Output Noise (RTO) At gain=100 1 Hz to 2 kHz Input Noise Line Frequencies Output Offset-Tare Range Drift Common Mode Rejection Gain=40 (DC-60 Hz) Gain=250 (DC-60 Hz) Rated Output (2k load) Output Impedance DC to 2 kHz Dynamic Response DC to –3 dB two pole Bessel Filter Common Mode Input Voltage Bridge Supply Input 40-250 200 ppm/°C 3 µV/°C ±
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C. Turn on the AC source supply to the DCM 460. D. Set the required EXCITATION supply voltage to the load cell by adjusting B+ ADJUST. III. Calibration Procedure for Zero Voltage Adjustment A. Jumper the + and - input terminals, pins 8 and 9, together. B. Connect a voltmeter across the output, pins 11 and 10. C. Adjust the COARSE OFFSET and the FINE OFFSET potentiometers for the desired ZERO voltage. IV. Full Scale Voltage Adjustment A.
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The sense lines minimize variations in output voltage with changes in load current or lead resistance. It should be noted that if the sense feature is not being used, terminal 1 must be connected to terminal 2. Terminals 3 and 4 must be connected also. The supply will provide up to 120 mA of output current. These features make the unit ideal for most common strain gage bridge circuits of 120, 350, and 500 Ohms. The supply has short circuit protection to protect it against short-term faults.
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Filter Roll Off Frequency The table in Figure 4 shows the values for C1 and C2 to set the 3 dB filter frequency. A printed circuit board is included for convenient mounting of the two capacitors. Use X7R ceramic or foil type capacitors. Filter C1 C2 Frequency To Pin 11 To Pin 10 2000 Hertz None None 200 Hertz 0.068 μF 0.022 μF 20 Hertz 0.68 μF 0.22 μF 9.4 Hertz 1.5 μF 0.47 μF Figure 4.
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Figure 5.