Counter

Features & Benefits

CMC251

• 1 Hz to 100 MHz (CH 1), 80 MHz to 1.3 GHz (CH 2)
• ±1 ppm Time Base
• Period Average, Period, Frequency, Totalize Self-test
• Display Hold
• Remote Start/Stop
• One Year Warranty

Applications

• Training
• Manufacturing
• Production Test
• Field Repair
• Bench Calibration and Repair
• Product Design
• Laboratory and Research
• Education

CMC251

The CMC251 1.3 GHz Multifunction Counter measures the frequency of sine, square and triangle waves from 1 Hz to 1.3 GHz. The CMC251 also provides period, totalize and pulse width measurements. The counter has two input channels. Channel A is a standard 1 MΩ input for frequency measurements up to 100 MHz. Channel B is a 50 Ω terminated input for use in high-frequency systems. This counter is of interest to radio amateurs because of its ability to measure high-frequency systems. The temperature-compensated, crystal-controlled time base is stable to ±1 part per million per year.

Characteristics

Channel A

Frequency Range - 1 Hz to 100 MHz.

Sensitivity - 20 mV_RMS, 1 Hz to 30 MHz; 50 mV_RMS, 30 MHz to 100 MHz.

Attenuation - 3 V to 42 V (HI); 50 mV to 5 V (LO).

Max. Input Voltage - 1 Hz to 5 MHz: 42 V pk. 5 MHz to 100 MHz: 4.9 V pk.

Low Pass Filter - -3 dB at 100 kHz.

Impedance - 1.0 MΩ, paralleled by 40 pF.

Channel B

Frequency Range - 80 MHz to 1.3 GHz.

Sensitivity - 5 mV_RMS, 80 MHz to 600 MHz; 15 mV_RMS, 600 MHz to 900 MHz; 35 mV_RMS, 900 MHz to 1.3 GHz.

Impedance - 50 Ω.

Max. Input Voltage - 1 V_RMS.

Period

Range - Direct: 0.4 µs to 1.0 s. Prescale: 0.04 µs to 1.0 s.

Resolution - Direct: 100 ps to 100 ns. Prescale: 10 ps to 10 ns.

Min. Pulse Width - Direct: 0.2 µs. Prescale: 20 ns.

Frequency Range - Direct: 1 Hz to 2.5 MHz. Prescale: 1 Hz to 25 MHz.

Events Averaged (N) - 1, 10, 100, 1000, 10,000 cycles.

Totalize Range - 0 to 99,999,999.

Pulse Width

Range - 0.25 µs to 0.5 s.

Period Range - 100 ps to 100 ns.

Events Averaged (N) - 1, 10, 100, or 1000 cycles.

Time Base Stability

Temperature - <1 ppm from 0 °C to 40 °C.

10% Line Voltage Change - <0.4 ppm.

Accuracy

Frequency - ±(time base error + 1 count).

Period - ±(time base error + 1 count + trigger error).

Pulse Width - ±(time base error + 1 count + trigger error + 10 ns).

Plus

Selectable Slope - No.

Ratio CH A: CH B - No.

Display Hold - Yes.

Remote Start/Stop - Yes.

Time Interval CH A: CH B - No.

Safety - UL1244, CSA231, EN61010-1.

EMC - Meets Directive 89/336/EEC.

Ordering Information

CMC251

1.3 GHz Frequency Counter with High Stability Time Base.

Includes: Operator's manual, US power cord, one year warranty.

Available Accessories

10X Probe, 250 MHz - Order P6106A.

Tektronix Measurement Service

Tektronix CAL and REP service programs allow you to prepurchase genuine Return to Tektronix Services - ask your Distributor for details.