ETC_196
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SCXI Isolated Universal Input SCXI Isolated Universal Input Modules NI SCXI-1121, NI SCXI-1122 • Isolated analog inputs • Isolated voltage and current excitation • Signal inputs from millivolts to ±250 V • Lowpass filtering • Shunt calibration • NI-DAQ driver software simplifies configuration, measurements, and scaling SCXI-1121 • 4 isolated input channels • 4 isolated excitation channels • 250 Vrms working isolation per channel • Offset nulling and shunt calibration with SCXI-1321 SCXI-1122 • 16 channels • 100 S/s (4 kHz filter), 1 S/s (4 Hz filter) • 2 excitation sources • 480 Vrms working isolation per channel Operating Systems • Windows 2000/NT/XP Recommended Software • LabVIEW • LabWindows/CVI • Measurement Studio • VI Logger Driver Software • NI-DAQ 7 Data Acquisition and Signal Conditioning Overview The National Instruments SCXI-1121 and SCXI-1122 modules are designed for a wide variety of sensor and signal inputs requiring isolation. The NI SCXI-1121 offers independent jumper-configurable isolation amplifiers, filters, and excitation sources for each channel. The SCXI-1122 offers an isolation amplifier, filter, and excitation source for all channels. Both SCXI-1121 and SCXI-1122 modules offer at least 250 Vrms working isolation and can acquire strain, RTD, thermocouple, millivolt, volt, 250 V, 0 to 20 mA, and 4 to 20 mA current input signals. Both modules can multiplex their channels into a single channel of the controlling DAQ device. The SCXI-1121 also offers parallel-mode operation. If you are specifically interested in strain measurements, consider using the NI SCXI-1520 Universal Strain Gauge Input Module. For thermocouple measurements, consider using the NI SCXI-1102 Thermocouple Input Module. For RTD measurements, consider using the SCXI-1102 in combination with the SCXI-1581 Current Excitation Module or the PXI-4070 DMM with SCXI-1127 switch. Analog Input SCXI-1121 The analog inputs of the SCXI-1121 consist of four isolated instrumentation amplifiers. You can configure each channel independently using jumpers for input ranges of ±2.5 mV to ±5 V. You can extend the input range for each channel to ±250 VDC/ ±250 VAC with the SCXI-1327 terminal block. Each channel also includes a lowpass filter that you can configure using jumpers for 4 Hz or 10 kHz. You can sample channels at a rate up to 333 kS/s (3 µs per channel in multiplexed mode). Each channel offers transducer-specific features such as bridge completion, configurable voltage and current excitation, bridge balancing, and shunt calibration depending on the configured terminal block. Each channel is individually isolated with a working voltage limit of 250 Vrms between channels or channel to earth. Finally, the SCXI-1121 is CE certified as double insulated, Category II, for 250 Vrms of operational isolation. SCXI-1122 The SCXI-1122 consists of 16 relay multiplexers that route the input channels to a single isolated instrumentation amplifier and lowpass filter. You can program all inputs together for a range of ±5 mV to ±250 V. You can program the lowpass filter setting for all input channels for either 4 Hz or 4 kHz. With this relay multiplexer architecture, you are limited to a maximum sampling rate of 100 S/s for the 4 kHz filter setting, and 1 S/s for the 4 Hz filter setting on all channels in your scan list. Thus, the SCXI-1122 is not intended to be used for the scanning of multiple channels. It should be used to acquire multiple samples from a single channel before acquiring from the next channel. This module also offers cold-junction compensation, bridge completion, and a single voltage and current excitation source with remote sensing. You can configure the SCXI-1122 for 4-wire scanning mode, accepting up to eight 5 k devices. You can also connect up to 16 devices in series. Each channel is individually isolated with a working common-mode voltage of 250 Vrms between channels or 480 Vrms channel to earth. Finally, the SCXI-1122 is CE certified as double insulated, Category II, for 250 Vrms of operational isolation. Table 1. Signal Compatibility National Instruments • Tel: (800) 433-3488 • Fax: (512) 683-9300 • info@ni.com • ni.com

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SCXI Isolated Universal Input Modules Both the SCXI-1121 and SCXI-1122 can read the cold-junction sensor from a compatible terminal block that offers a cold-junction sensor. In multiplexed mode, both modules must read the sensor as a separate analog input operation. This is usually done before the start of a continuous acquisition. For thermocouple measurements, the SCXI-1102, 1112, and 1125 an sample the cold-junction sensor in the same scan as the thermocouples, to provide better accuracy. SCXI-1122 The SCXI-1122 offers only one voltage and one current excitation channel for transducers...

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Analog Multiplexer Scan Clock SCXIbus Connector Gain Select Digital Interface and Control Lowpass Filter Lowpass Filter Figure 1. SCXI-1121 Block Diagram Relay Multiplexer Lowpass Filter Lowpass Filter Front Signal Connector Relay Multiplexer CH15– Mux Counter IEX + IEX – Sense + VEX + VEX – Sense – Configuration Register Voltage Source Digital Interface and Control Status Register Current Source Calibration EEPROM Figure 1. SCXI-1122 Block Diagram National Instruments • Tel: (800) 433-3488 • Fax: (512) 683-9300 • info@ni.com • ni.com SCXIbus Connector Rear Signal Connector Rear Signal...

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SCXI Isolated Universal Input Modules Part Number 777687-20 Type Screw terminals Front-mounting Screw terminals Front-mounting Screw terminals Front-mounting Screw terminals Front-mounting Screw terminals Front-mounting BNC connectors Front-mounting Screw terminals DIN-rail mount Screw terminals DIN-rail mount Solder pins Front-mounting Special Functions _ Offset nulling and shunt calibration for strain gauges Extended voltage input range (to 250 Vrms) Isothermal construction BNC connectors AC coupling (configurable per channel) DIN rail mount Isothermal construction DIN rail mount AC/DC...

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