Rohde & Schwarz R&S UPP, Руководство пользователя

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Getting Started
R&S
®
UPP
73 User Manual 1411.1055.32 ─ 10
Possible Damage or Destruction of Input Circuits
The generator of the audio analyzer can generate analog output voltages with an RMS
of up to 14 V. These levels can damage or even destroy sensitive input circuits.
There is an option in the "Generator Config" panel for limiting the analog output volt-
age. For measurements on sensitive circuits, it is advisable to set an appropriately low
value in the "Max Voltage" field; this value then applies to all analog output signals,
irrespective of the signal shape.
The pulse level of the digital audio signals can be up to 8.5 V. Although the risk of
destruction is generally much smaller than for analog circuits, care must still be taken
when making settings for activating digital circuits.
3.2.2 Avoiding Hum Loops
It is generally known in audio engineering that analog circuits must always be set up in
such a way that hum signal pick-up is avoided. For this reason, it is important that a
ground connection (grounding contact) be provided at only one point in the entire cir-
cuit.
Generator:
Pin 1 is not connected at the XLR connector. Symmetric (Bal) and asymmetric (Unbal)
output are electronically floating (exception: Bal with switched-on output divider!). The
output can be placed on ground (grounding it) by connecting Pin 3 to the ground.
Analyzer:
Starting with serial numbers 120100, 140100, 180100, Pin 1 is connected to ground via
a capacitor, thereby connecting the pin with instrument ground only in relation to HF.
This avoids formation of hum loops if the external connection connects pin 1 and 3 with
each other.
To prevent any additional inadvertent ground connection being established via the gen-
erator, it is designed as electronically floating (exception: balanced operation with
switched-on output divider). Pin 1 of the XLR connector is not connected. To prevent
establishing any additional inadvertent ground connection via the audio analyzer when
connecting the test setup with the analyzer inputs, Pin 1 of the XLR cable must not be
connected with ground of the test setup (applies only to instruments with serial num-
bers lower than 1x0100, x = 2, 4, 8).
There are, however, some applications where the audio circuit to be tested is set up
without any ground connection at all. It may be necessary to create a defined ground
connection especially if hum pick-up is suspected. When connecting the UPP analyzer
Important Information for Measurements