BRUEL & KJAER 2663, Technical Documentation Manual

Page: 27 / 54

Chapter 2 — Operation
Circuit Adjustment for Velocity Measurement
Preamplifiers Types 2663 and 2663 B
User Manual
Brüel & Kjær
20
The suggested value for

is 0.37.
The value of the capacitance
C
is fixed at 330
×
10
–9
F.
The formula can be simplified, and a value for resistor can be found in the fol-
lowing formula (2.6.2):
(2.6.2)
The value of resistor can then be calculated from the following formula (2.6.3):
(2.6.3)
2.6.3 Velocity Sensitivity
The velocity sensitivity S
V
of the preamplifier can be found through the following
formula (2.6.4):
(2.6.4)
Calculation of the gain (acceleration sensitivity) is covered in section 2.5.4 .
Shown in Fig.2.14 are both the measured and calculated responses of the preamplifi-
ers when used as an integrator. In this example, the measured frequency response of
the preamplifiers compares well with the ideal curve. However, component toleranc-
es may cause some deviation from the calculated frequency response of the integra-
tor. It is always recommended to compare the measured frequency response with the
calculated response. If the deviation is too large, the resistor values can be changed
slightly; alternatively the value of


or F
LP
can be changed and the resistor values
recalculated.
R
H
2
R
H
2
7.36 10
5

F
HP
--------------------------
  
=
R
H
1
R
H
1
2.33 10
11

R
H
2
F
HP

-----------------------------
  
=
S
V
Gain 2
 
F
HP
mV
m s

------------ =