Table of Contents
Advertisement
BC
D@teetl0n Mod©
DC detection offers greater power measurement accuracy and the ability to characterize oscillators and
modulation sensitive devices. To use DC detection, you must first set the DC measurement mode on the
HP 8757A. There is also a zeroing operation used in the DC mode that compensates for the effects of
DC drift and temperature fluctuations.
The ability to make DC measurements and the softkeys specific to DC mode are not automatically
accessible. The HP 8757A must acknowledge the presence of an AC/DC detector either at preset, or via
the [CONFIG SYSTEM] softkey in the CAL menu.
1.
Connect the equipment as shown in Figure 2-2.
On the HP 8757A:
2.
Press [PRESET].
During preset:
«
The analyzer reads each input port and identifies the detector or bridge connected to it (AC/DC
or AC only).
®
The HP 8757A enables the DC mode softkeys (when an AC/DC detector or bridge is identified).
Now you can access [DC DET ZERO] (in the CAL menu) and [MODE AC/DC] (in the SYSTEM
menu).
3.
To turn on the DC mode, press [SYSTEM] and select the softkey [MODE AC/DC]. AC dims and DC
lights up.
When you select DC mode with the softkey [MODE AC/DC], the analyzer turns OFF the source internal
squarewave modulation (HP 8350B) and disables the analyzer's rear panel modulation drive output
(used with the HP 8340A/41A).
You can also have the analyzer read the inputs without using [PRESET]: Press [CAL] and select the
softkey [CONFIG SYSTEM].
If you remove and/or exchange a detector, you must reconfigure the system, using either [PRESET] or
the softkey [CONFIG SYSTEM], so that the correction factors match the port and device.
DC lereing.
When you make a DC mode measurement, you should perform a zeroing operation
to compensate for the effects of DC drift and temperature fluctuations (this is not required for AC
detection). The zeroing operation eliminates small DC voltages from the diode detector that would
otherwise cause amplitude measurement errors at low (-40 dBm and below) power levels.
On the HP 8757A:
1.
Press [CAL] and select [MORE] [DC DET ZERO]. The analyzer displays SELECT DC DET ZERO.
2.
Select [AUTOZROJ. The analyzer displays AUTOZERO IN PROGRESS ... and then AUTOZERO
COMPLETED.
Operation
Advertisement
Table of Contents
