Chapter 9 Specifications

To Calculate Total Measurement Error

Understanding the “ % of range ” Error o

”” ” ” 5

 

 

o ° ” ” 3

 

3

 

Vhh’s 24-hour dc voltage specification.

 

 

Range Error

Range

Range

Input Level

(% of range)

Error Voltage

 

 

 

 

10 Vdc

10 Vdc

0.0004

40 μV

10 Vdc

1 Vdc

0.0004

40 μV

10 Vdc

0.1 Vdc

0.0004

40 μV

 

 

 

 

To compute the total measurement error,

add the reading error and range error. You can then convert the total measurement error to a “percent of input” error or a “ppm (part-per- million) of input” error as shown below.

a

= Total Measurement Error

× 100

 

Input Signal Level

 

 

= Total Measurement Error

× 1,000,000

 

Input Signal Level

 

Example: Computing Total Measurement Error

Assume that a 5 Vdc signal is input to the Vhh on the 10 Vdc range. Compute the total measurement error using the 90-day accuracy specification of ±(0.0020% of reading + 0.0005% of range).

Reading Error

=

0.0020%

x

5 Vdc

= 100 μV

Range Error

=

0.0005%

x

10 Vdc

= 50 μV

Total Error

=

100 μV + 50 μV

= ± 150 μV

 

 

 

 

 

=

± 0.0030% of 5 Vdc

 

 

 

 

 

=

± 30 ppm of 5 Vdc

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HP 34970A manual Understanding the % of range Error o, × 1,000,000