HBK Bruel & Kjaer 3670-A-082, User Manual

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Brüel & Kjær Production Test USB DAQ Type 3670 – User Manual 10
Fig.2.4
BKSV USB Audio Tool
installer
4) Click Next and follow the instructions in the installation tool. When complete, click Finish .
5) If not already done, connect Type 3670 to the PC via USB and switch it on.
2.4 Direct Input with CCLD Power On
The default CCLD power setting is ON for Type 3670. If you want to connect a direct signal from, for
instance, a signal generator, to a Type 3670 input channel, there is a risk of distorting the signal as
some generators cannot accept (sink) the 4 mA CCLD current.
To avoid this distortion without having to switch off the CCLD power, you can use a DC current
blocker made of a capacitor and a resistor with a value of 2.7 to 3 k

.
Fig.2.5
CCLD current blocker
diagram
Inserting the DC current blocker, as shown in Fig.2.5, between your generator and the input of
Type 3670 will load the generator with the 2.7 k

.
⚑
Hint:
It is possible to loop back a Type 3670 output channel to an input channel using a a BNC cable
modified to include a DC current blocker as shown in Fig.2.5. The output will be able to accept the
load, even if you are running several inputs in parallel.
220 uF
2.7 k
CCLD Input