I. Product Introduction

NI SCXI-1122 is a 16-channel isolation relay multiplexer module of the SCXI series. It adopts the "16-channel relay selection → single-channel isolated amplifier + low-pass filter" architecture, specifically designed for multi-channel, low-rate, and high-isolation requirements for sensor signal conditioning. It can interface with voltages ranging from millivolts to ±250V, thermocouples, RTDs, strain bridges, 4-20mA currents, etc. It integrates isolation excitation, cold junction compensation, and bridge completion functions. It is discontinued (Legacy), but can be repaired or purchased as a second-hand / in stock.

II. Model Interpretation

SCXI: Instrument Signal Conditioning Expansion Series

1122: Basic model, 16-channel isolation multiplexer (single amplifier shared)

Part Number: 776572-22

III. Technical Parameters (Official, 25℃)

Channels and Isolation

Channels: 16 single-ended / differential isolation inputs, isolation between channels and ground

Working Isolation Voltage: 250Vrms continuous (between channels) / 480Vrms (to ground), CE certified double insulation, CAT II

Input Range (Software Uniform Setting): ±5mV to ±250V

Input Impedance: 1GΩ (powered on) / 100kΩ (powered off)

Common Mode Rejection Ratio CMRR: ≥100dB (DC to 60Hz)

Signal Conditioning

Amplifier: Single-channel isolated amplifier (shared by 16 channels)

Gain: Programmable by software, covering millivolt to high voltage signals

Filter: Software selectable 4Hz or 4kHz low-pass (all channels unified), 3-pole RC, NMRR at 60dB at 4Hz

Excitation: 1-channel isolated voltage / current excitation (3.333V ± 0.04%, 1.0mA ± 0.04%), with remote sensing

Sampling and Precision

Scan Rate: ≤100S/s for all channels when filtered at 4kHz; ≤1S/s for relay switching rate limitation when filtered at 4Hz; (all channels)

Sampling Mode: Switch between single channels multiple times (not suitable for high-speed polling)

Non-Linearity: ≤±0.01% FSR

Gain Error (Calibrated): ≤0.05% reading

Temperature Drift: ≤10ppm/℃

Cold Junction Compensation (CJC): Built-in, supports thermocouples

Bridge Completion: Supports strain bridge, RTD measurement

Electrical and Environmental

Power Supply: 5V ≤ 30mA; ±15V ≤ 200mA (backplane of the chassis)

Operating Temperature: 0 to 50℃ (standard commercial grade)

Storage Temperature: -40℃ to +85℃

Humidity: 5% to 90% without condensation

Size / Weight: 1U SCXI standard (30×173×203mm) / approximately 0.8kg

IV. Interface and Communication Configuration

Front Panel: 96-pin DIN C connector, connects to SCXI-1322 (16-channel isolation terminals, with CJC and excitation) or SCXI-1303 (general terminals)

Back Panel: 50-pin ribbon cable connector, connects to the SCXI chassis backplane bus, transmits data, timing, and power supply

Communication: No independent communication port, relies on the SCXI bus to communicate with the backend DAQ device (such as PCIe-6251), driven and configured parameters, and data reading by NI-DAQmx

Cabling: Supports floating ground / grounded signals, compatible with thermocouples, RTDs, strain gauges, 4-20mA transmitters, high-voltage DC

V. Core Functions

16-channel High Isolation Multiplexer: 250Vrms isolation between channels, single amplifier shared design, saves cost and chassis space, suitable for low-speed multi-channel acquisition. Ultra-wide input range: ±5mV to ±250V, covering from weak signals to industrial high voltage, no additional conditioning required, simplifying the system.

Integrated sensor excitation and compensation: built-in isolated voltage/current excitation, CJC, bridge completion, directly supporting thermocouples, RTDs, strain bridges, one card for multiple uses.

Dual-band low-pass filtering: 4Hz (anti-interference against industrial frequency) / 4kHz (preserving dynamic signals) software selectable, suitable for static / quasi-static measurements.

High anti-interference capability: channel isolation + high common-mode rejection ratio, completely eliminating ground loops, suitable for industrial strong interference environments.

Six. Application scenarios

Multi-channel temperature monitoring: 16 channels of thermocouples / RTD temperature measurement (such as heat treatment furnaces, pipelines, tanks), with SCXI-1322 terminals to achieve CJC and isolation.

Strain and pressure measurement: signal conditioning for strain gauges, weighing sensors, pressure transmitters (4-20mA), suitable for structural testing, industrial weighing.

High-voltage / floating ground signal acquisition: high-voltage DC, signals from devices with different ground potentials, isolation protection for DAQ and personnel safety.

Low-speed high-density acquisition system: laboratories, production lines, equipment condition monitoring, with many channels, low rate, high interference requirements.

Seven. Usage and maintenance instructions

Usage instructions

Installation: Power off, insert SCXI chassis, tighten fixing screws; supports hot swapping, can replace modules during operation.

Connection: Firmly connect isolation terminals, good insulation,严禁 mixing high and low voltage connections； use SCXI-1322 for thermocouples， enable CJC； strain bridges need excitation and bridge completion.

Configuration： NI-DAQmx sets input range， filtering bandwidth， excitation mode； scan rate strictly limited by filtering level (4kHz ≤ 100S/s， 4Hz ≤ 1S/s).

System： 68-pin SCSI cable connects SCXI chassis and DAQ； multi-chassis cascading sets a unique address to avoid conflicts.

Maintenance instructions

Environment： Keep dry， prevent condensation； away from strong electromagnetic sources， vibration sources.

Regular inspection： Check terminals， connectors， cables every quarter， for any looseness， oxidation， damage； clean surface dust.

Calibration： Once a year， focus on calibrating gain， linearity， CJC； for thermocouple / strain measurement scenarios， calibrate once every half year.

Fault handling： Data drift → calibration； signal jump → check grounding， shielding， terminal tightening； abnormal excitation → check excitation circuit and wiring.