HP 53132A Assembly And Service Manual page 241

Chapter 8 HP 53181A Specifications
Measurement Specifications (Continued)
Measurement Specifications (Continued)
Frequency Measurement Example:
Given an HP 53181A 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


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 10
=
–
×
4.0 10
=


 ± ×
Measurement Error 4.0 10
=


( ± ×
4.1 10
=
( ± ×
= 4.1 10
±
63.1 mHz
=
Which is to say that the HP 53181A would display results in the range 15 MHz ±63.1 mHz. Note however that the dominant error is the Time
Base Error. If an even higher stability time base is available to the instrument 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 ±0.8 MHz (1 sigma) which
determines the number of digits displayed.
Assembly-Level Service Guide
± ×

t

± acc ± ×

--------------------------- -
2 ------------------------------------------------------------------------------------------ -

Gate Time 
Gate Time
×
+
9 10
× ( × – )
3 5 10
+
9

× – 10
× (

1 10 s 4 500 10
– 9
± ± × 
-------------------------- - 2 ------------------------------------------------------------------------------ -

1s 
1s
– 9 – 12 – 12
± × ( × ×
2 4.47 10 50 10
+
9 10
– ± × – ) ×
1.09 10 15MHz
2 2
× ( × )
4 t 2 Trigger Error
+
res
+
×
Number of Samples
2
– 12 – 12
× ) ( × ) ×
s 2 0 50 10
+
----------------------------- -
+
× , 1s
200 000
) ) ×
15MHz
 
t
jitter ×
 
--------------------------- -
Frequency
Gate Time  
 
s
  ×
15MHz
 
8-7