I. Product Introduction

NI SCXI-1127 is a high-density high-voltage armature relay matrix/multiplexer module on the SCXI platform, providing flexible channel topology configuration, suitable for low-voltage precision and high-voltage industrial signal switching. It is discontinued (Legacy), repairable or available for purchase as second-hand / in stock.

II. Model Interpretation

SCXI: Instrument Signal Conditioning Expansion Series

1127: Basic model, 32 channels (2-wire) high-voltage matrix/multiplexer (armature relay)

Part Number: 776572-27

III. Technical Parameters (Official, 25°C)

Channels and Topology

Basic: 32 channels 2-wire configuration

Software selectable topology: 1×32 (2-wire), 2×16 (2-wire), 4×8 (2-wire), 1×64 (1-wire), 1×16 (4-wire), 4×8 matrix (with SCXI-1332)

Relay type: Armature relay, low thermal offset

Voltage and Current

Channel-to-channel / ground isolation: 250Vrms continuous (CAT II)

Maximum switching voltage: 250Vrms / 300VDC

Switching current: 1A (continuous); 2A (peak)

Current-carrying capacity: 2A (continuous)

Electrical and Performance

Bandwidth: 11MHz (typical)

On-resistance: <1Ω (typical)

Thermal offset: <5μV (low-voltage measurement)

Switching time: typical 5ms (pull-in) / 3ms (pull-out)

Scan Rate: Maximum 100 channels / second

Relay Life: ≥100,000 times (rated load)

Environment and Mechanics

Power Supply: +5V, ±15V (SCXI backplane)

Operating Temperature: 0～50°C

Storage Temperature: -40°C～+85°C

Humidity: 5%～90% no condensation

Size / Weight: 1U SCXI standard (30×173×203mm) / approximately 0.7kg

IV. Interface and Communication Configuration

Front Panel: 96-pin DIN C connector, compatible with SCXI-1332 (matrix terminals), SCXI-1327 (high-voltage attenuation) and other terminal blocks

Back Panel: 50-pin ribbon cable connector, includes high-voltage analog bus (HVAB), can share signals with other SCXI high-voltage modules

Communication: Based on SCXI bus for communication with DAQ/DMM; driven and controlled by NI-SWITCH for relay switching, supports development environments such as LabVIEW, C/C++, Visual Basic

Trigger: Supports hardware trigger synchronization, minimum pulse width 500ns

V. Core Functions

Flexible Topology Configuration: Single module realizes multiplexing, matrix and independent switching modes, covering 1-wire / 2-wire / 4-wire measurement, suitable for RTD, thermocouples, high-voltage signals.

High-Voltage Isolation and Safe Switching: 250Vrms isolation, supports 250VAC/300VDC signals, protects low-voltage measurement equipment and operators.

Low-Voltage Precision Measurement: Armature relay low thermal offset (<5μV), suitable for millivolt-level weak signals, strain bridge, RTD, etc. precision measurement.

High-Density Channel Expansion: Single module up to 64 single-wire or 32 differential channels, cascading multiple modules can build large-scale ATE test systems.

High-Speed Scan and Synchronization: 100 channels / second scan rate, hardware trigger synchronization, suitable for multi-channel parallel testing and data acquisition.

VI. Application Scenarios

Industrial High-Voltage Signal Switching: 250VAC/300VDC signals multi-channel selection for power equipment, motors, frequency converters, etc. Precision multi-channel measurement: 4-wire/2-wire scanning measurement for RTD, thermocouple, strain gauge, and millivolt-level sensors.

ATE automatic test system: Multi-station functional testing on the production line, circuit board testing, sensor calibration system.

Data acquisition expansion: Cooperate with DMM (such as NI 4070) to expand high-voltage and high-density channel measurement capabilities.

VII. User and Maintenance Instructions

User Instructions

Installation: Power off and insert the SCXI chassis and fix it; hot-swappable, but high-voltage operation is recommended to be powered off for maintenance.

Connection: Low-voltage signals use ordinary terminals, high-voltage signals use SCXI-1327/1332 terminals; strictly distinguish high and low voltage circuits, and connect with excessive pressure.

Configuration: Select topology, channel list, and scan rate with NI-SWITCH; enable HVAB isolation in high-voltage mode to avoid ground loops.

System: Connect 68-pin SCSI cable between the SCXI chassis and DAQ/DMM; set a unique address for each module cascade to avoid conflicts.

Maintenance Instructions

Environment： Keep dry and ventilated， away from strong electromagnetic interference and vibration； avoid high temperature， humidity， and corrosive gases.

Regular Inspection： Check terminals， cables， and connectors every quarter for looseness， oxidation， and damage； clean surface dust to ensure heat dissipation.

Calibration： Once a year， calibrate conductance resistance， thermal offset， and isolation performance； calibrate once every half year in precise measurement scenarios.

Fault Handling： Channel not working → Check relay contacts and terminals； drift increases → Perform self-calibration； isolation failure → Shut down to test insulation and relay status.