7

Chapter 7 HP 53131A/132A Specifications

Measurement Specifications (Continued)

Measurement Specifications (Continued)

Frequency Measurement Example:

Given an HP 53132A with a High Stability Oven that was calibrated 3 days ago, measure a 15 MHz square wave signal (which has negligible trigger error) with a 1 second gate time. Compute the measurement error to within 2-sigma confidence.

Measurement Error = Systematic Uncertainty ± 2 × RMS Resolution

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

± Time Base Error ±

tacc

± 2

4 ×

tres2

+ (2 × Trigger Error2)

 

 

tjitter

⎞⎞

× Frequency

=

Gate---------------Time------------

× ------------------------------------------------------------------------------------------

+ ---------------------------

⎟⎟

 

 

Gate Time

×

Number of Samples

 

Gate Time⎠⎠

 

Number of Samples = 200,000 since Frequency is greater than 200kHz and gate time equals 1 second

Time Base Error = Temperature Stability + 3 Days × Daily Aging Rate

=2.5 × 109 + 3 × (5 × 1010)

=4.0 × 109

 

 

9

 

1 × 10

11

s

 

4

×

(225

×

10

12

s)

2

 

(2 × 0)

 

3 × 10

12

⎞⎞

 

Measurement Error =

± 4.0

× 10

±

 

± 2

× ⎜

 

+

+

 

s

× 15MHz

 

-----------1s--------------

-

----------------------------

×--------------------------------------------------

-----------1s--------------

-⎟⎟

 

 

 

 

 

 

 

1s

 

200, 000

 

 

 

⎠⎠

 

=4.0 × 109 ± 2 × (2.01 × 1012 + 3 × 1012)) × 15MHz

=4.0 × 109 ± 1 × 1011) × 15MHz

=±60.2 mHz

Which is to say that the HP 53132A would display results in the range 15 MHz ±60.2 mHz. Note however that the dominant error is the Time Base Error. If an even higher stability time base is available or if the instrument can be source locked to the 15 MHz signal, then this error term can be substantially reduced. The measurement resolution under these conditions is ±75 μHz (1 sigma) which determines the number of digits displayed.

7-8

Assembly-Level Service Guide