NI SCXI-1338

Description

Detailed Parameter Table

NI SCXI-1338

Product introduction

The National Instruments SCXI-1338 is a specialized current-input terminal block designed to bridge industrial current sensors and NI’s SCXI signal conditioning modules, enabling accurate current-to-voltage conversion for data acquisition (DAQ) systems. As a key component of NI’s SCXI ecosystem, it addresses the common challenge of integrating 4–20 mA/0–20 mA current loops—widely used in industrial sensors—with voltage-focused DAQ devices.

At its core, the SCXI-1338 features 16 differential channels, each equipped with a precision 249 Ω resistor. This resistor converts incoming current signals to measurable voltage (e.g., 4–20 mA becomes 0.996–4.98 V), making the data compatible with SCXI modules like the SCXI-1125 (strain gauge module) or SCXI-1120 (general-purpose signal conditioner). Its high-voltage isolation (300 VDC) and rugged design ensure reliability in harsh industrial environments, while front-panel mounting simplifies wiring and maintenance.

In automation systems, the SCXI-1338 eliminates the need for external signal converters, reducing system complexity and signal loss. By pairing with compatible SCXI modules and DAQ devices (e.g., NI PCI-6025E), it creates a seamless workflow for measuring current-based sensor data—from motor load monitoring to environmental sensor networks.

Core advantages and technical highlights

Precision Current-to-Voltage Conversion: Each channel of the SCXI-1338 includes a 249 Ω resistor with 0.1% tolerance and 10 ppm/°C temperature stability. This ensures consistent conversion of 4–20 mA current signals to 0.996–4.98 V voltages, minimizing measurement errors caused by resistor drift. For example, in a water treatment plant, this precision guarantees accurate readings from 4–20 mA flow sensors, ensuring chemical dosing systems operate within optimal ranges.

High-Voltage Isolation and Ruggedness: With 300 VDC channel-to-ground isolation, the SCXI-1338 protects sensitive SCXI modules and DAQ devices from voltage transients common in industrial settings (e.g., power surges in manufacturing lines). Its compliance with UL 61010-1 standards further validates its safety for use near high-voltage equipment, making it a reliable choice for energy, automotive, and heavy industry applications.

Seamless SCXI Ecosystem Integration: The SCXI-1338 is purpose-built to work with NI’s SCXI-1120, SCXI-1120D, SCXI-1125, and SCXI-1126 modules. This compatibility eliminates compatibility issues and simplifies system design—engineers can directly mount the SCXI-1338 to the front of an SCXI-1125 module, reducing wiring time and ensuring signal integrity between the terminal block and conditioner.

16-Channel Scalability: With 16 differential channels, the SCXI-1338 supports multi-sensor deployments without additional hardware. In a factory automation setup, this means monitoring 16 separate motor current sensors with a single terminal block—cutting costs and reducing rack space compared to single-channel converters. The differential input design also rejects common-mode noise, critical for industrial environments with electromagnetic interference (EMI) from motors or power lines.

Typical application scenarios

Industrial Motor Health Monitoring: In automotive manufacturing plants, the SCXI-1338 connects 4–20 mA current sensors on assembly line motors to the SCXI-1120 module and NI PCI-6220 DAQ device. It measures motor load current in real time—an increase in current may indicate bearing wear or belt tension issues. The SCXI-1338’s precision ensures early detection of anomalies, preventing unplanned downtime and reducing maintenance costs.

Environmental Sensor Networks: For wastewater treatment facilities, the SCXI-1338 integrates 4–20 mA dissolved oxygen (DO) sensors with the SCXI-1126 module. It converts DO sensor current signals to voltage, which is then logged via a DAQ system. The SCXI-1338’s high-voltage isolation protects the system from water treatment plant electrical noise, while its 16 channels allow monitoring of multiple treatment tanks simultaneously—ensuring compliance with environmental regulations.

Energy Grid Monitoring: In solar power plants, the SCXI-1338 measures 0–20 mA current from inverter output sensors, pairing with the SCXI-1125 module to track power generation. Its rugged design withstands outdoor cabinet temperatures (0–55 °C), and precision resistors ensure accurate data for grid load balancing. By eliminating external converters, the SCXI-1338 reduces signal delay, enabling real-time adjustments to solar panel output.

NI SCXI-1338

Related model recommendations

NI SCXI-1125: Strain gauge signal conditioning module—directly compatible with the SCXI-1338. It conditions the voltage signals from the SCXI-1338 for high-precision measurements (e.g., strain + current monitoring in structural testing).

NI SCXI-1120: General-purpose signal conditioner—works with the SCXI-1338 to amplify low-voltage converted signals from 4–20 mA sensors, ideal for industrial process control.

NI PCI-6025E: Multi-function DAQ device—acquires voltage data from the SCXI-1338 (via SCXI modules) for PC-based analysis, suitable for lab or factory floor setups.

NI SCXI-1001: 12-slot SCXI chassis—houses the SCXI-1338 and compatible modules, providing power and synchronization for high-channel-count systems.

NI BNC-2110: BNC terminal block—complements the SCXI-1338 in mixed-signal systems, converting DAQ voltage outputs to BNC for oscilloscope verification of SCXI-1338 conversion accuracy.

NI SCXI-1339: 8-channel current terminal block—smaller sibling of the SCXI-1338 for low-channel applications (e.g., portable test kits), offering the same precision but fewer channels.

Installation, commissioning and maintenance instructions

Installation Preparation: Before installing the SCXI-1338, ensure the compatible SCXI module (e.g., SCXI-1125) is securely mounted in an SCXI chassis (e.g., SCXI-1001). Use a Phillips-head screwdriver to attach the SCXI-1338 to the front panel of the SCXI module, aligning the terminal block’s pins with the module’s connector. Use 26–14 AWG shielded wires for sensor connections—ground the shield at the chassis end to reduce EMI. Ensure the environment meets the SCXI-1338’s temperature (0–55 °C) and humidity (10–90% non-condensing) requirements to avoid performance issues.

Maintenance Suggestions: Monthly, inspect the SCXI-1338’s screw terminals for looseness or corrosion—tighten terminals with a torque wrench (5 in-lbs) to prevent signal loss. Use compressed air to remove dust from terminals, as debris can cause resistance buildup. If current readings are inaccurate, verify the 249 Ω resistors with a precision DMM (e.g., NI PXI-4071)—replace the SCXI-1338 if resistors deviate beyond 0.1% tolerance. For long-term reliability, recalibrate the connected SCXI module annually, as the SCXI-1338’s performance depends on the module’s calibration.

Service and guarantee commitment

National Instruments backs the SCXI-1338 with a 2-year standard warranty, covering defects in materials and workmanship. This warranty reflects NI’s confidence in the terminal block’s durability, even in industrial environments. For technical support, NI’s global team provides 24/7 assistance via email and online portals—helping users troubleshoot wiring issues, verify compatibility with SCXI modules, or optimize signal integrity.

NI also offers accredited calibration services for the SCXI-1338, ensuring its resistors and isolation meet original specifications. Extended warranty plans (3–5 years) are available for critical applications, including priority repair and replacement. Users gain access to free resources: the SCXI-1338 user manual, application notes (e.g., “Integrating 4–20 mA Sensors with SCXI Systems”), and video tutorials—empowering seamless integration and long-term performance.