CNT-91/91R
Advanced Frequency & Time Interval Analyzer
- Category: Advanced Frequency & Time Interval Analyzer
- Manufacturer: Pendulum Instruments
- Standard frequency measurement range: 0.001 Hz to 400 MHz (2 channels)
- Optional frequency extension ceiling: 3 GHz, 8 GHz, 15 GHz or 20 GHz (third channel option)
- Time resolution (single shot): 50 ps (single shot); timestamp resolution 35 ps
- Frequency resolution: 12 digits/s; displayed to 14 digits
- Data sheet: Download PDF
- External link: Official product page
Overview
The CNT-91/91R combines frequency measurement, time interval analysis and signal calibration in one high-end instrument, for metrology and engineering work where measurement accuracy matters most. The standard frequency range covers 0.001 Hz to 400 MHz and can be extended by option to 3 GHz, 8 GHz, 15 GHz or 20 GHz, which covers calibration from a low-frequency oscillator to a microwave source. Continuous zero-dead-time timestamping gives 50 ps single-shot time resolution per measurement and frequency resolution of up to 12 digits/s, with values displayed to 14 digits, so very small changes in frequency and time are captured. The CNT-91R carries an ultra-stable rubidium oscillator, which shortens warm-up considerably and provides a high-accuracy portable calibration reference without a separate external clock. Built-in statistics cover mean, minimum, maximum, standard deviation and Allan deviation (ADEV), and the graphical histogram and trend displays let an engineer judge the stability and the quality of the signal under test as the measurement runs. USB and GPIB (IEEE 488.2 / SCPI) are standard, the GPIB transfers up to 4,000 measurement results per second for seamless integration into an automated test system, and HP53131A emulation mode keeps compatibility with an older test environment.
Key features
- Class-leading measurement speed — 250,000 measurements per second straight into internal memory, storing up to 3.5 million results. That lifts throughput in production test and R&D verification, and can save as much as 90% of the time a test system spends measuring.
- 50 ps time resolution — Continuous zero-dead-time timestamping gives 50 ps single-shot time resolution and frequency resolution of up to 12 digits/s, resolving the smallest frequency drift and phase jitter in an oscillator.
- Advanced statistics and graphical analysis — Built-in mean, standard deviation, min/max and Allan deviation (ADEV) calculations, presented as a histogram and a trend plot, so an engineer can judge the long-term stability of the source under test quickly.
- CNT-91R: built-in rubidium timebase — The CNT-91R integrates an ultra-stable rubidium oscillator that reaches a high-accuracy reference after a short warm-up — the natural choice for calibrating frequency sources and for portable metrology work, with no external atomic clock needed for traceable calibration.
- Wide coverage, flexible extension — Two standard channels cover 0.001 Hz to 400 MHz, and an optional third channel extends to 20 GHz, so one instrument handles low-frequency oscillators, RF sources and microwave frequency sources alike.
- Complete interfaces and system integration — USB and GPIB (IEEE 488.2 / SCPI/1999) are fitted as standard, the GPIB carrying up to 4,000 results per second; HP53131A emulation mode lets the CNT-91 replace a legacy counter and drop into an existing automated test environment without changes.
Typical applications
- Jitter characterization of PLLs and oscillators — Designing an OCXO, a rubidium source or a PLL synthesizer, an engineer uses the CNT-91's modulation domain analysis with TimeView to capture minute frequency drift over time through continuous zero-dead-time measurement at 250,000 per second. Three statistical views — numeric, histogram and trend — show the whole behaviour from slow drift to fast jitter, replacing the oscilloscope-plus-spectrum-analyzer routine.
- High-speed frequency verification on an ATE line — In automated test equipment on an electronics production line, the CNT-91 streams results to the host continuously over GPIB in block mode at 15k readings per second, and its 53131/53132 compatible mode replaces an existing counter without rewriting the test program. Batch verification throughput for frequency, period, pulse width and rise time rises sharply as a result.
- CNT-91R: portable frequency calibration in the field — With its built-in ultra-stable rubidium clock timebase (typical total uncertainty <2.5x10⁻¹⁰ one year after calibration), the CNT-91R lets a calibration engineer work on site without an external frequency standard, verifying the master oscillator of a communications base station, satellite ground station equipment or avionics. The graphical display gives live calibration guidance, which shortens the time spent tuning to frequency.
Key specifications
Key specifications for CNT-91/91R, as published by Pendulum Instruments. For the full datasheet or a customized configuration, please get in touch.
| Standard frequency measurement range | 0.001 Hz to 400 MHz (2 channels) |
|---|---|
| Optional frequency extension ceiling | 3 GHz, 8 GHz, 15 GHz or 20 GHz (third channel option) |
| Time resolution (single shot) | 50 ps (single shot); timestamp resolution 35 ps |
| Frequency resolution | 12 digits/s; displayed to 14 digits |
| Measurement rate | 250,000 measurements/s; up to 3.75M results in internal memory |
| GPIB bus transfer rate | Up to 4,000 results/s |
| Input impedance | 1 MΩ ∥ 20 pF or 50 Ω (switchable) |
| Input sensitivity | 15 mVrms (DC to 200 MHz); 35 mVrms (300 to 400 MHz) |
| Timebase options (CNT-91) | OCXO 0.01 ppm/month or ultra-high-stability OCXO 0.003 ppm/month |
| Timebase (CNT-91R) | Built-in ultra-stable rubidium oscillator |
| Programmable output frequency | 0.5 Hz to 50 MHz |
| Dimensions / weight | 395 x 210 x 90 mm / 2.7 kg |
| Power supply | 90 to 265 V, 45 to 440 Hz |
Frequently asked questions
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