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CNT-91/91R Zero Dead Time Frequency Counter is capable of real-time continuous data streaming of measurement results through the GPIB/USB interface during the measurement process, rather than transmitting the measurement results after the measurement is complete. It is the first instrument in the frequency counter industry to have a dynamic measurement/analysis system. Additionally, among general-purpose frequency counter/time interval testers, the CNT-91 has the best performance indicators.
Outstanding Performance Indicators:
- Fast Data Transfer Speed: The high GPIB/USB bus transfer speed significantly reduces the testing time of automatic test systems (ATE). In Talker Only mode, the measurement result transfer speed for a single measurement is up to 4k readings per second. Additionally, in Block mode, the instrument can quickly transfer measurement results in the form of continuous data streaming.
- Zero Dead Time Measurement: Due to the capability of zero dead time measurement, the instrument provides back-to-back measurements of period/frequency and ensures accurate calculation of Allan variance.
- High Measurement Resolution: High measurement resolution is crucial for product development and production testing. The CNT-91 series products have a single-shot measurement time resolution of 50ps and a frequency measurement resolution of 12 digits/second, ensuring the capture of subtle changes in time and frequency. The measurement results can be displayed with up to 14 digits.
- Modulation Domain Analysis (MDA): When the CNT-91 series products are combined with TimeViewTM software, the CNT-91 transforms into a high-performance modulation domain analyzer. By utilizing the internal memory with a capacity of up to 3.5M readings and a measurement speed of 250k readings per second, the instrument can capture rapidly changing frequencies of the measured signal in real-time.
- Built-in Programmable Pulse Output: The CNT-91 series products feature a built-in programmable pulse output, providing a pulse signal with fast rise time. The output signal frequency range is from 0.5Hz to 50MHz. The pulse output can be used as a reference frequency output, external step/tigger source, or a general-purpose pulse signal source.
CNT-91/91R vs. CNT-90 Performance Comparison:
Performance | CNT-91/91R | CNT-90
Graphical Display | Yes | Yes
Frequency Resolution| 12 digits/s | 12 digits/s
Time Resolution | (Single-shot)| 50ps | 100ps
Voltage Resolution | 1mV | 3mV
Measurement Speed (to internal memory) | 250k/s (3.5M) | 250k/s (750k)
Talker Only Output (GPIB/USB) | 4k/s | None
Individually Triggered Measurements | 650/s | 500/s
Block mode Transfer Speed | 15k/s | 5k/s
Frequency/Period, Time, Phase, Voltage, Duty Cycle, Pulse Width, Rise Time | Yes | Yes
Accumulated, TIE, Zero Dead Time Frequency/Period | Yes | No
Programmable Pulse Output | Yes | No
Continuous Measurement | Yes | No
Time Base (CNT-91 vs CNT-90) | OCXO (opt) | OCXO (opt)
Time Base (CNT-91R vs CNT-90) | Rubidium Atomic Clock | OCXO (opt)
Technical Specifications for CNT-91 and CNT-91R:
Measurement Functions
All measurements are displayed with a main parameter value and several small auxiliary parameter values (lower resolution). Some measurements can only be read as auxiliary parameters.
Frequency A, B, C
Mode: Normal Mode, Back-to-Back Mode
Range: Inputs A, B: 0.002Hz to 400MHz
Input C (option): Up to 3, 8, 14, or 20GHz
Resolution: 12 digits, 1s measurement time (Normal Mode)
11 digits, 1s measurement time (Back-to-Back Mode)
Auxiliary Parameters: Vmax, Vmin, Vp-p
Pulse Train Frequency A, B, C (Option 10 and 14/14B)
The carrier frequency and pulse repetition frequency (PRF) of a repetitive pulse train signal can be measured without external control signals and with selectable start-on-standby delay.
Function: Frequency (Hz) of short pulse train
PRF (Hz)
Range: Inputs A, B, C: See frequency technical specifications
Minimum Duration of Short Pulse Train (Channels A and B):
Minimum 40ns (80ns for frequencies above 160MHz)
Minimum Number of Pulses in Short Pulse Train:
Inputs A or B: 3 (6 for frequencies above 160MHz)
Input C: 3 times the predetermined scaling factor
PRF Range: 0.5Hz to 1MHz
Start Delay: 10ns to 2s, 10ns resolution
Auxiliary Parameter: PRF
Period A, B, C
Mode: Single-Shot Mode, Averaging Mode
Back-to-Back Mode
Range: Inputs A, B: 3.3ns to 1000s (Single-Shot, Averaging)
4us to 1000s (Back-to-Back Mode)
Input C (option): 10ns to 330,125,70, or 50ps
Resolution: 50ps (Single-Shot); 12 digits/second (Averaging)
Auxiliary Parameters: Vmax, Vmin, Vp-p
Ratio A/B, B/A, C/A, C/B
Range: 10^-9 to 10^11
Input Frequencies:
Inputs A, B: 0.1Hz to 400MHz
Input C (option): Up to 3, 8, 14, or 20GHz
Auxiliary Parameters: Frequency 1 and Frequency 2
Time Interval A-B, B-A, A-A, B-B
Range:
Normal Calculation: 0ns to +106s
Clever Calculation: -106s to +106s
Resolution: 50ps (Single-Shot)
Minimum Pulse Width: 1.6ns
Frequency Range: Up to 160MHz
Clever Calculation: Used to determine the sign of clever time interval measurements (A before B or A after B)
Positive Pulse Width and Negative Pulse Width A, B
Range: 2.3ns to 106s
Minimum Pulse Width: 2.3ns
Auxiliary Parameters: Vmax, Vmin, Vp-p
Rise and Fall Time A, B
Range: 1.5ns to 106s
Trigger Levels: 10% and 90% of signal amplitude
Minimum Pulse Width: 1.6ns
Auxiliary Parameters: Transition Time, Vmax, Vmin
Time Interval Error (TIE) A, B
In standard period back-to-back measurements, the time interval error can be calculated using the formula: TIE(k) = k × REF T - Ti Σ, where Ti = single
Input and Output Technical Specifications
Inputs A and BFrequency Range:
DC Coupling: DC to 400MHz
AC Coupling: 10Hz to 400MHz
Impedance: 1MΩ // 20pF or 50Ω (VSWR ≤ 2:1)
Trigger Edge: Positive or Negative
Maximum Channel Skew: 500ps
Sensitivity:
DC to 200MHz: 15mVrms
200MHz to 300MHz: 25mVrms
Attenuation: ×1, ×10
Dynamic Range (×1): 30mVp-p to 10Vp-p within ±5V window
Trigger Level: Displayed on the screen
Resolution: 1mV
Uncertainty (×1): ±(15mV + 1% of trigger level)
Auto Trigger Level: Automatically set to 50% of input signal amplitude (10% and 90% for rise/fall time measurements)
Auto Delay: Minimum Delay Window (Delay Compensation)
Analog Anti-Aliasing Filter: Rated at 100kHz, RC type
Digital Low-Pass Filter: 1Hz to 50MHz cutoff frequency
Maximum Safe Voltage:
1MΩ: 350V (DC+ACpk) up to 440Hz, decreasing to 12Vrms at 1MHz (×1)
50Ω: 12Vrms
Connector: BNC
Input C (Option 10)Operating Input Voltage Range:
100MHz to 300MHz: 20mVrms to 12Vrms
0.3GHz to 2.5GHz: 10mVrms to 12Vrms
2.5GHz to 2.7GHz: 20mVrms to 12Vrms
2.7GHz to 3.0GHz: 40mVrms to 12Vrms
Scaling Factor: 16
Impedance: 50Ω nominal, VSWR < 2.5:1
Maximum Safe Voltage: 12Vrms with pin diode protection
Connector: N-type (female)
Input C (Option 13)Operating Input Voltage Range:
200MHz to 300MHz: 40mVrms to 7Vrms (typical)
300MHz to 500MHz: 20mVrms to 7Vrms
0.5GHz to 3.0GHz: 10mVrms to 7Vrms
3.0GHz to 4.5GHz: 20mVrms to 7Vrms
4.5GHz to 6.0GHz: 40mVrms to 7Vrms
6.0GHz to 8.0GHz: 80mVrms to 7Vrms
Scaling Factor: 256
Impedance: 50Ω nominal, VSWR < 2.5:1
Maximum Safe Voltage: 7Vrms
Connector: N-type (female)
Input C (Options 14 and 14B)
Frequency Range: 0.2GHz to 14GHz (Option 14)
0.25GHz to 20GHz (Option 14B)
Operating Input Voltage Range:
250MHz to 500MHz: -21dBm to +27dBm
0.5GHz to 14GHz: -27dBm to +27dBm
14GHz to 18GHz: -27dBm to +27dBm (Option 14B
)
18GHz to 20GHz: -21dBm to +27dBm (Option 14B)
Scaling Factor: 128
Impedance: 50Ω nominal, VSWR < 2.0:1
Modulation Tolerance: >90% within sensitivity range
Maximum Safe Voltage: +27dBm
Connector: Precision N-type (female)
Optional Accessories
Option 11/90: Rear Panel Input
Option 22/90: Rack Mount Kit
Option 27: Soft Carrying Case
Option 27H: Durable Hard Carrying Case
Option 29/90: Time View Modulation Domain Analysis Software for CNT-90
Option 90/01: Calibrated Certificate with Standard Oscillator
Option 90/06: Calibrated Certificate with Oven Oscillator
Option 90/07 (for CNT-91R only): Calibrated Certificate with Rubidium Oscillator
Option 90/00: Calibrated Certificate with Aging/Weekly Holdover
Option 95/03: Extended 3-Year Warranty
Option 95/05: Extended 5-Year Warranty
OM-90: English User Manual (Printed Version)
PM-90: English User Programming Manual (Printed Version)
SM-90: English Service Manual
GS-90-EN: English Quick Start Guide
GS-90-FR: French Quick Start Guide
GS-90-DE: German Quick Start Guide
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The most high-performance frequency counter/time interval analyzer
● Continuous data streaming through the bus during measurement, instead of transferring data after measurement completion
● Zero-dead-time frequency/period measurement
● Fastest GPIB/USB bus transfer speed: 650 measurements/second (single-shot mode); 4k measurements/second (Talker mode); 15k measurements/second (block mode)
● High measurement resolution: 50ps time resolution, 12 digits/second frequency resolution
● Advanced graphical display features, including: numerical statistics display, histograms, trend plots, and modulation domain analysis
● High-speed data transfer between the instrument and the 3.5M internal data memory at 250k measurements/second
● Built-in programmable pulse output with frequency range of 0.5Hz to 50MHz
● CNT-91R equipped with a rubidium atomic clock as the internal timebase
Powerful measurement tools
● Regardless of the user's measurement tasks, the measurement performance of the CNT-91/91R counter/time interval analyzer surpasses any other frequency counter on the market.
● Graphical display: The instrument provides graphical display capabilities for measurement results, including histograms, trend plots, numerical statistics, and modulation domain analysis. These graphical displays allow users to gain a deeper understanding of the distribution of random signals and the variation of measured signal parameters over time (from slow drift to rapid jitter and modulation).
● Standardized GPIB and USB interface: The standardized interface settings eliminate the need for installing GPIB interface on the PC. The GPIB interface operates in two different modes: SCPI/GPIB and 53131A emulation mode, making it easy to replace existing frequency counters in automated test systems without the need for extensive command reprogramming.
● Wide frequency measurement range: With options, the frequency measurement range of the CNT-91 series can reach up to 20GHz. Users can use the CNT-91 series to measure the frequency of continuous microwave signals as well as short pulse trains, with a minimum pulse duration of 40ns.
● Menu-driven setup: Menu-driven setup reduces the risk of operator errors. The display of multiple parameter results provides valuable signal information, reducing the need for additional instruments such as digital voltmeters (DVMs) and oscilloscopes.
● When users need to measure, analyze, and calibrate time and frequency parameters, the high-performance CNT-91/91R frequency counter/time interval analyzer is the only tool that meets their requirements.
CNT-91R Frequency Calibrator/Analyzer
The CNT-91R is a comprehensive and high-performance frequency source calibrator with advanced measurement resolution and analysis capabilities, as well as an ultra-stable rubidium clock as the internal timebase. The CNT-91R features portability and short warm-up time, making it an ideal portable integrated frequency calibrator/analyzer.
Outstanding graphical display capabilities
One of the unique features of the CNT-91 is its graphical display and menu-driven setup. Non-experts can easily perform correct setups without the risk of major operator errors.
The instrument employs a multi-parameter display mode, showing additional auxiliary measurement values below the main measured values. For example, while displaying the measured frequency value, it also shows auxiliary parameters such as Vmax/Vmin/Vp-p. While displaying the measured phase value, it shows auxiliary parameters such as frequency and attenuation. This multi-parameter display mode allows users to obtain direct answers to common questions without the need for additional test instruments, such as "What is the attenuation and phase shift of this filter?"
Measurement results can be displayed both numerically and graphically. Graphical displays (histograms, trend plots) provide a deeper understanding of jitter characteristics. Graphical displays also offer users a
better visualization of the variation of the measured object over time (from slow drift to fast modulation) through trend plots.
Statistical results of the same data set can be displayed in three different ways: numerical display, histograms, and trend plots. It is easy to capture and switch between the three different display modes of the same data.
When adjusting a frequency source to a given limit, the graphical display provides fast and accurate intuitive calibration guidance.
Rear Panel Inputs and Outputs
Reference Input: 1, 5, or 10MHz, 0.1 ~ 5 Vrms sine wave, impedance ≥ 1kΩ
Reference Output: 10MHz, >1 Vrms sine wave into 50Ω
Arm Input: All measurement functions armed
Impedance: Approximately 1kΩ
Frequency Range: DC ~ 80MHz
Pulse Output: Programmable control through front panel, GPIB, or USB
Modes: Pulse out, Gate open, Alarm out
Period: 20ns ~ 2s (10ns steps)
Pulse Width: 10ns ~ 2s (10ns steps)
Output: TTL level, 50Ω output impedance, rise time of 2ns
Rear Panel Measurement Inputs: A, B, C (Option 11/90)
Impedance: 1MΩ//50pF or 50Ω (VSWR ≤ 2:1)
Connector: SMA type (female) for Rear Panel Input C
Additional FeaturesTrigger Inhibit
Delay Range: 20ns ~ 2s, 10ns resolution
External Arm/Disarm
Modes: Arm, Disarm, Arm/Disarm
Input Channels: A, B, or E - Rear Panel
Maximum Repeat Rate for Arm Signal:
Channels A, B: 160MHz
Channel E: 80MHz
Start Delay Range: 20ns ~ 2s, 10ns resolution
Statistics Processing
Functions: Maximum, Minimum, Average, Δmax-Min, Standard Deviation, Allan Deviation
Display: Numeric, Histogram, or Trend Plot
Sample Size: 2 ~ 2×109 samples
Limiting: OFF to disable or capture data above/below limits or within/outside limit range
Measurement Step
Step Time Range: 4us ~ 500s
Math Processing
Functions: (K*X+L)/M and (K/X+L)/M, where X is the current reading and K, L, and M are constants set via keyboard or using a fixed reference value (0 X).
Other Features
Measurement Time: 20ns ~ 1000s for frequency, pulse train, and period average functions. For other measurement functions, the measurement time is a single period.
Timebase Reference: Internal, External, or Automatic
Display Hold: Holds the result until Restart is triggered for a new measurement cycle.
Limit Alarms: Graphical display on the front panel and/or SRQ messages via GPIB, plus pulse output connector.
Limits: Lower Limit, Upper Limit
Setting: OFF to disable or set to trigger alarms above/below limits or within/outside limit range
Alarm Status: STOP or CONTINUE
Display: Numeric and Graphical
Stored Instrument Settings: 20 instrument settings can be saved and recalled using internal non-volatile memory. User protection available for 10 settings.
Display: Backlit LCD graphical screen used for menu control, numeric readouts, and status information display.
Digits: 14-digit display in numeric mode.
Resolution: 320*97 pixels.
GPIB Interface:
Compatibility: IEEE 488.2-1987, SCPI 1999 53131A compatibility mode.
Interface Functions: SH1, AH1, T6, L4, SR1, RL1, DC1, DT1, E2
Maximum Measurement Rate:
Via GPIB: 15k readings/second (Block mode)
4k readings/second (Talker only mode)
650 readings/second (Individual Get triggered)
To internal memory: 250k readings/second
Internal Memory
Capacity:
CNT-91: Up to 3.5 million readings.
USB Interface:
USB Version: Full-Speed 2.0 (11Mbit/s)
Metrology
Mode: Calibration without opening, menu control
Frequency Calibration: 0.1, 1, 5, 10, 1.544, and 2.048MHz
General SpecificationsEnvironmental Data
Standard: Complies with MIL-PRF-28800F, Class 3
Operating Temperature: 0°C to +50°C (CNT-91)
0°C to +45°C (CNT-91R)
Storage Temperature: -40°C to +71°C
Humidity: 5% to 95% (10°C to 30°C)
5% to 75% (30°C to 40°C)
5% to 45% (40°C to 50°C)
Altitude: Up to 4600 meters
Vibration: Random and sine vibration testing per MIL-PRF-28800F, Class 3 standard
Shock: Half-sine 30G testing per MIL-PRF-28800F, bench handling standard
Transportation Drop Test: Tested per MIL-PRF-28800F standard using durable hard-shell and low-hardness shipping containers
Reliability: Mean Time Between Failures (MTBF) of 30,000 hours (calculated value)
Safety: Complies with EN61010-1, Pollution Degree 2, Measurement Category I, CSA C22.2No1010-1, CE standards
Electromagnetic Compatibility (EMC): Complies with EN61326 (1997); A1 (1998) standard and enhanced testing levels per EN50082-2, Group 1, Class B, CE standards.
Power Requirements
Base Model: 90 ~ 265Vrms, 45 ~ 440Hz, <40W
CNT-91R:
Warm-up (12 minutes): 90 ~ 265Vrms, 45 ~ 440Hz, <80W
Operating: 90 ~ 265Vrms, 45 ~ 440Hz, <50W
Dimensions and Weight
Width x Height x Depth: 210×90×395mm (8.25×3.6×15.6 in)
Weight: Net weight of 2.7 kg (5.8 lbs)
Shipping weight approximately 3.5 kg (7.5 lbs)
Ordering Information
Main Unit
CNT-91 400MHz, 50ps Counter/Time Interval Analyzer, including standard timebase.
CNT-91R 400MHz, 50ps Counter/Time Interval Analyzer, including rubidium timebase.
Instrument also includes: 18 months of product warranty, power cord, user documentation CD, and calibration certificate.
Input Frequency Options
Option 10 3GHz Input C
Option 13 8GHz Input C
Option 14 14GHz Input C
Option 14B 20GHz Input C
Timebase Options (CNT-91 only)
Option 19/90 Intermediate Stability Oven Timebase; 0.06ppm/month
Option 30/90 High Stability Oven Timebase; 0.01ppm/month
Option 40/90 Ultra-High Stability Oven Timebase; 0.003ppm/month
Power Requirements
Base Model: 90 ~ 265Vrms, 45 ~ 440Hz, <40W
CNT-91R:
Warm-up (12 minutes): 90 ~ 265Vrms, 45 ~ 440Hz, <80W
Operating: 90 ~ 265Vrms, 45 ~ 440Hz, <50W
Dimensions and Weight
Width x Height x Depth: 210×90×395mm (8.25×3.6×15.6 in)
Weight: Net weight of 2.7 kg (5.8 lbs)
Shipping weight approximately 3.5 kg (7.5 lbs)
Ordering Information
Main Unit
CNT-91 400MHz, 50ps Counter/Time Interval Analyzer, including standard timebase.
CNT-91R 400MHz, 50ps Counter/Time Interval Analyzer, including rubidium timebase.
Instrument also includes: 18 months of product warranty, power cord, user documentation CD, and calibration certificate.
Input Frequency Options
Option 10 3GHz Input C
Option 13 8GHz Input C
Option 14 14GHz Input C
Option 14B 20GHz Input C
Timebase Options (CNT-91 only)
Option 19/90 Intermediate Stability Oven Timebase; 0.06ppm/month
Option 30/90 High Stability Oven Timebase; 0.01ppm/month
Option 40/90 Ultra-High Stability Oven Timebase; 0.003ppm/month
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Documentation
CNT-91/91R Counter/Time Interval Tester/Analyzer Calibrator【PDF】data
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