Timebase Temperature Stability

(Manual Performance Test for E8257N only)

This manual test verifies the temperature stability of the signal generator’s internal timebase.

A measurement is made of the signal generator’s 10 MHz reference signal using a counter. The counter can be locked to an external reference or be equipped with a high precision reference oscillator. Since this is a relative frequency measurement only the aging specification of the measurement’s reference oscillator is critical. After changing the ambient temperature of the signal generator, another frequency measurement is made and the change in frequency is compared to the specification.

A frequency counter with an ovenized frequency reference should be used. If the frequency counter does not have an ovenized frequency reference, a stable external frequency reference should be used. Because this is a relative frequency measurement, only frequency aging and not absolute frequency accuracy is applicable. In addition, an environmental chamber is required to control the signal generator’s ambient temperature. Only the signal generator and not the additional test equipment should be placed in the environmental chamber.

Required Test Equipment

Test Equipment

Recommended Models

Alternate Model(s)

Frequency Counter

53230A

53132A

53132A Opt 001, 010, or 012 if no frequency standard is used

53230A Opt 010 if no frequency standard is used

Frequency Standard (optional)

Microsemi 5071A

  

 

Connections and Setup Procedures

  • All equipment requires a one hour warmup period to ensure accurate performance.

  • In the following test setup, cables are designated as solid lines and direct connections are designated as dashed lines.

  1. Allow the unit under test (signal generator) to warm up for at least 1 hour.
     

  2. The frequency reference used for the test equipment (either the frequency counter if equipped with an ovenized reference or the external frequency reference) should be adequately warmed up. The measurement uncertainty for this test is based on the applicable frequency reference aging rate, which in turn is based on how long the frequency reference has been warmed up.
     

  3. Connect all test equipment as shown.   

 

 

 

 

  1. Set the frequency counter to measure frequency with a gate time of 1 sec:

    1. Press [Freq & Ratio] to select frequency measurement. “FREQUENCY 1” should be displayed. If not, continue to press [Freq & Ratio] until it is.

    2. Press [Gate & ExtArm]. If “GATE: TIME” is not displayed, press the up arrow key until it is.

    3. Press [Gate & ExtArm] again to display “TIME: ”. Use the arrow keys to adjust the gate time to 1 sec, then press [Enter].

    4. Press [Freq & Ratio] to return to the frequency measurement display.

 

Measurement

  1. With the environment chamber set to 25°C, make a frequency measurement of the signal generator’s frequency reference (f25).

  2. Change the signal generator’s ambient temperature to 0°C. Allow the signal generator sufficient time to reach temperature equilibrium (one hour is recommended) and measure the signal generator’s frequency reference. (f0).

  3. Change the signal generator’s ambient temperature to 50°C. Allow the signal generator sufficient time to reach temperature equilibrium (one hour is recommended) and measure the signal generator’s frequency reference. (f50).

  4. Calculate the difference, Δf, between the maximum and minimum values of f0, f25, and f50.

  5. Calculate the temperature stability as shown below, and compare to the specification.

                                      

Expanded Uncertainty

For a coverage factor of 2, which includes 95.45% of the population of measurement uncertainty values, the overall uncertainty will be:

               2 × 2.8 × 10-10 = 5.6 × 10-10.

For f = 10 MHz, the corresponding frequency uncertainty is:

                5.6 × 10-10 × 107 = 0.006 Hz.

Specification

                Temperature Stability <  2 × 10-6, or 20 Hz.

 

In Case of Difficulty

If this performance test fails, perform the following steps in order:

  1. Check the equipment setup (see above). If the setup is incorrect, make the necessary corrections and rerun the Performance Test.

  2. If this test fails with the equipment set up properly, refer to the troubleshooting section of the signal generator's service guide. If you do not have a printed copy of the service guide (Option OBW), one is available either on the CD-ROM that came with your signal generator shipment or on the Keysight Website.

  3. If you cannot correct the problem using the troubleshooting procedures in the Service Guide, obtain service from Keysight Technologies. Refer to Contacting Keysight Technologies.