Keysight (Agilent) 42090A Open Termination, 4-Terminal Pair

The Keysight (Agilent) 42090A Open Termination is a 4-terminal pair calibration accessory that establishes a defined open circuit condition for high-precision impedance measurements. It is a critical verification tool for LCR meters and impedance analyzers, enabling accurate compensation of residual and parasitic impedances inherent in test fixtures. By providing a known open reference, the 42090A allows engineers to baseline measurements and quantify fixture effects such as stray capacitance and inductance - essential for reliable characterization of both low and high impedance devices.

Technical Specifications

• Connection Type: 4-Terminal Pair with BNC connector interface


• Physical Dimensions: 94 mm (width) × 31 mm (height) × 67 mm (depth)


• Weight: 120 g (0.26 lbs)


• Function: Open circuit termination for calibration and performance verification

Key Features

• Provides repeatable open circuit reference for impedance measurement calibration


• Enables parasitic element compensation in 4-terminal pair test configurations


• Compact form factor suitable for bench and automated test environments


• BNC connector interface for direct integration with impedance measurement systems

Typical Applications

• Calibration and verification of 4-terminal pair LCR meters


• Performance validation of impedance analyzers


• Fixture characterization and de-embedding workflows


• Baseline measurement establishment in precision impedance testing


• Quantification of test setup parasitic elements

Compatibility & Integration The 42090A is compatible with Keysight precision impedance instruments including the E4980A, E4980AL, E4981A, and E4990A families. Legacy compatibility extends to Agilent 4285A, 4288A, and 4294A systems. Reference the applicable instrument operation or service manual for detailed integration procedures and calibration protocols.