Keysight Technologies (Agilent HP) Probes

For general-purpose debugging, passive probes provide high input resistance and rugged construction. The Keysight 1161A is a 500 MHz passive probe with a 10:1 attenuation ratio and a typical 10 pF input capacitance. It features an ID pin for automatic scaling identification when connected to compatible oscilloscopes like the Infiniium 54800 Series.

When high-speed or differential signal integrity is critical, active probes reduce capacitive loading while maintaining multi-gigahertz performance. The Keysight 1169A InfiniiMax II active probe delivers a 12 GHz bandwidth with a 33 ps calculated rise time (10% to 90%). It features a differential input resistance of 50 kΩ and uses the AutoProbe I interface for direct power and offset control from the host oscilloscope. For lower frequency differential measurements, the Keysight 1141A active FET probe provides a 200 MHz bandwidth and 2 MΩ differential input resistance. Because it uses a proprietary connector, it must be paired with the Keysight 1142A Probe Control and Power Module to provide the required ±15 V and +5 V DC supply voltages and offset control.

RF design and high-frequency in-circuit measurements require exceptionally low capacitive loading to prevent circuit disruption. The Keysight 85024A active probe operates from 300 kHz to 3 GHz (usable down to 100 kHz). It features an input capacitance of less than 0.7 pF shunted by a 1 MΩ nominal resistance, and terminates in a 50 Ω Type-N male connector.

For low-frequency RF up to VHF, the Keysight 41800A covers 5 Hz to 500 MHz with 0 dB gain. It offers a typical input capacitance of 3 pF (probe alone), which drops to 1 pF when using the included 10:1 or 100:1 divider accessories. The 41800A receives power through a standard HP 4-pin probe power connector or an external supply.

Electromagnetic compatibility (EMC) and EMI troubleshooting rely on localized H-field measurements to trace emissions. The Keysight 11940A and Keysight 11941A are passive, handheld magnetic-field probes. Both utilize a balanced dual-loop sensor design to reject common-mode electric (E-field) fields, and feature 50-ohm SMA female connectors.

The Keysight 11940A is calibrated for high-frequency troubleshooting from 30 MHz to 1 GHz, while the Keysight 11941A covers the low-frequency range from 9 kHz to 30 MHz. To cover the entire spectrum, the Keysight 11945A close-field probe set contains both individual probes inside a custom hard carrying case, providing calibrated measurements from 9 kHz up to 1 GHz.

Logic analyzer hardware requires secure, high-density connections that do not alter the timing of fast digital buses. The Keysight E5346A is a 34-channel single-ended logic analyzer probe. It connects to the target board using a standard 38-pin Mictor footprint, routing 32 data channels and 2 clock/strobe channels to the logic analyzer via 40-pin cable connectors. This probe provides a 100 kΩ input impedance and 3.0 pF of equivalent load capacitance to ensure clean state and timing analysis.