SCS-824 4-pole bessel SCS-825 4-pole butterworth - bandwidth 5Hz to 1275Hz

SCS-826 4-pole bessel SCS-827 4-pole butterworth - bandwidth 185Hz to 47.22kHz

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4-channel Strain Gauge Amplifier Module for the SCS-800 Signal Conditioning System

4 amplifiers/filters per module Independent corner frequency selector Independent gain control ±10V input and output Automatic DC offset compensation Offset guaranteed <1mV for all gain settings Differential output, proprietary DC transformer Onboard channel and module multiplexers Input cable shield drive

Overview

The SCS-824(5)(6)(7) provides 4 channels of strain gauge inputs for the SCS-800 signal conditioning system. It accommodates most strain-gauge types, from single-element quarter bridges to 4-element full bridges.  Using included SystemView software, you can adjust excitation voltage, input gain, offset nulling, and all other key functions.

Excitation Sources. The SCS-824(5)(6)(7)'s excitation source is a very stable Kelvin connected voltage. This excitation source features current limiting circuits to prevent damage from short-circuits or overloads and can be shut down. Selection can be made from one of four output voltages.

Completion Resistors. Physical locations are provided for bridge completion and calibration resistors. Bridge completion is selected through software for 1/4, 1/2 or full bridge. The SCS-824 provides completion resistors for 1/2 bridges, while 1/4 bridges resistors are user-supplied. resistors also are user-supplied and are connected to the bridge high and low sides. Each resistor can be independently grounded through software commands.

Input Amplifier. The SCS-824(5)(6)(7)'s two-stage instrumentation amplifier offers software-selectable gain settings from 1 to 1000. Both input and output offset errors are calibrated to zero at the factory.

Offset Adjustment. Auto-calibration of DC offset errors is accomplished via a feedback circuit which measures the DC offset on each channel, then compensates the input amplifier offset via an D/A converter. The SCS-804 system controller module stores correction parameters in non-volatile memory. An analog 4-pole low-pass filter provides superior low-noise and DC performance. The filter, which may be software bypassed, is available with Bessel or Butterworth characteristics and software-selectable cutoff frequencies from 5Hz to 1275Hz or from 185Hz to 47.22kHz.

Differential Output. A proprietary DC transformer circuit buffers output signals and provides true differential output with voltage compliance of ±12V. Because the circuit acts as a transformer, the output of the SCS-824 can drive long twisted-pair output cables with minimum interference from common-mode signals. This feature allows the SCS-824 module to be located up to 100 feet from the receiving instrument (A/D).

Output to A/D. The SCS-824(5)(6)(7) provides three means of attaching analog output signals to any data acquisition system. Each SCS-824(5)(6)(7) features a 50-pin output connector that can connect directly to an A/D board. outputs on a module are multiplexed together via software control available on the module output connector.addition, all four differential outputs of the SCS-824(5)(6)(7) module can be multiplexed onto the SCS-800 backplane under software control. A receiver on the SCS-804 controller board buffers the multiplexed signals from all installed modules, again buffers with a DC transformer buffer, then sends the signals out a front-panel connector. This provision provides a means to multiplex all channels together and out one differential output.The result is simplified cabling and elimination of the need for a separate relay module.