BRUEL & KJAER 2694A, Руководство пользователя

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16-channel Conditioning Amplifier Type 2694 – User Manual 20
l
Reduce the cable length
Calculating Maximum Cable Length for IEPE (DeltaTron) Transducers: The maxi-
mum cable length in metres for standard and non-standard accelerometer cables can
be calculated from
where,
I
s
=
supply current [mA]
f
=
frequency [kHz]
V
o
=
output voltage [V
peak
]
C
m
=
cable capacitance [pF/m]
Internal Signal Overload: Signal overloading inside Type 2694 amplifiers is effective-
ly detected by circuits that monitor the signal levels before each filter section and
after every amplifier stage.
Internal overloading can occur due to the nature of the input signal, or the selected
filters.
Transducer Setup
This menu allows you to select the type of input for DeltaTron/voltage or channel
disable. You can also specify transducer sensitivity and measurement units in this
setup menu. When a channel is disabled, its LEDs are not lit.
Note: Changing the sensitivity has no effect on the amplification; it is only informa-
tion for the user.
Transducer Type
Select Type in the main menu and use the cursor to select the desired channel.
DeltaTron mode is used for DeltaTron accelerometers or transducers with DeltaTron
compatible output, such as prepolarized microphones with DeltaTron Microphone
Preamplifier Type 2671. DeltaTron accelerometers have built-in preamplifiers. They
operate on a constant-current power supply and give output signals in the form of
voltage modulation on the power supply line. The main difference between the Del-
taTron and the direct voltage inputs is that the DeltaTron mode has a built-in cur-
rent generator that can supply a constant current of 6 mA to the transducer. Single-
ended or floating input modes can be selected.
L 140000
I
s
1 –
f V
o
C
m
× ×
-----------------------------
×
=
BE164411.book Page 20 Friday, May 18, 2001 11:51 AM