The Astronics/EADS/Racal 2461-Cd is a C-size VXI universal counter timer card delivering precision frequency, timing, and voltage measurements for automated test equipment, calibration labs, and R&D environments. This module functions as a direct replacement for legacy Racal 2461 variants and Keysight E1420A/B models. The -Cd configuration omits an internal oscillator, requiring external timebase sourcing.
## Technical Specifications
**Measurement Performance**
• Frequency measurement to 200 MHz with 9–10 digit/second resolution
• Time interval: 1 ns single-shot resolution; 100 ps average mode resolution
• Pulse characterization: automatic rise time, fall time, and pulse width measurement
• Phase measurement: automatic phase detection supported
• DVM voltage measurement: ±5.1 V standard range; ±42–51 V with ×10 attenuation; ±200 V with ×40 attenuation (2461A)
• Trigger resolution: 2.5 mV
## Key Features
• Automatic measurement functions: frequency, period, time interval, rise/fall time, pulse width, duty cycle, frequency ratio, totalize, phase, and DVM
• Nine-mode arming capability with selectable sources from external inputs or VXI TTL trigger lines
• Programmable measurement timeout for systems with intermittent or absent input signals
• Internal storage capacity: 14,000 readings
• Per-channel 50 kHz low-pass filters with selectable hysteresis for noise mitigation
• Adjustable sensitivity for low-level and noisy signal optimization
• Time Error Correction (TEC) and recipromatic techniques minimize measurement time without performance loss
## Typical Applications
Frequency and timing validation in production test; component characterization in R&D; precision voltage and phase measurements in calibration workflows; automated multifunction parameter acquisition in instrument racks.
## Compatibility & Integration
VXIbus C-size module. Functional replacement for Racal 2461 (Cd, Ce, S-2276B, S-2391B) and Keysight E1420A/B. Related -Ce variant includes TCXO; -Cf includes oven-controlled crystal oscillator.
