Manual - 8500A Series Peak Power Meter - Giga-tronics

Series 8500A Peak Power Meters
In the latter case, a high power coupler is required to attenuate the signal to a level that can be safely
measured by the detectors (less than +20 dBm). If the exact coupling factor of the coupler being used is
known, the Offset feature can then be used to subtract it out. Then the display will accurately show the
high power present at the device under test. However, the detectors only see the coupled power which has
been attenuated to avoid burning out the detector diode.
To offset the displayed power reading, press
8501A: [MENU] (3) [F1]
8502A: [MENU] (3) [F1] (ch A) or [F2] (ch B).
After the Offset function has been selected, enter the desired offset in dB and then press any Units key.
When the Offset function has been activated, an asterisk (*) will appear next to the FREQ indication in
the display to indicate that an offset is in use. (If the Cal Factor function is in use, the asterisk will be
next to the CF indication.)
The display will appear as:
*FREQ = nn.nGHz or *CF = n.nndB
2.8.4 CW Power Measurement
To make a CW measurement be sure that the PPM has warmed up for at least 30 minutes, and then
perform the following steps:
1. Select the CW Mode as described in Section 2.6.1.
2. Self-Calibrate the PPM as described in Section 2.7.
3. Determine that the power range to be measured will not exceed the maximum power capability
of the instrument (less than +23 dBm). If it will, connect an attenuator or coupler to the output
of the device under test to bring the power down into the range of the PPM, and use the
attenuator or coupler output as the measurement point for the detector attachment. If in doubt,
use a 10 dB attenuator. This should prevent a mild overload that might result only in detector
degradation rather than burn out.
4. Be sure the RF power of the source is completely OFF.
5. Connect the detector to the power source being measured.
6. Auto-Zero the detector by pressing [MENU] (1) [F3] [F2] [UNITS], or, if only channel B of a
Model 8502A is to be zeroed, press [MENU] (1) [F3] [F2] [CLEAR] [UNITS].
A beep indicates that a successful auto-zero has been accomplished. A double beep indicates
either there was RF power present at the detector input or there could be a failure. If a failure is
suspected, then run the Self-Test procedure in Section 2.15.
7. Upon successful completion of the auto-zero function, turn on the RF power of the source to be
measured.
8. Take into account the detector frequency response so that an accurate reading can be made at the
frequency of operation. If the External Frequency mode (i.e. PROM Table and Sweeper Back
Panel) is being used, this step is unnecessary. (See PROM Frequency Correction in
Section 2.8.2). The keystrokes are [FREQ] [nn.nn] [GHz]
If the PPM is in the PROM Table - User Supplied Frequency mode, nn.nn is the Carrier
Frequency in GHz. If the PPM is in the User Supplied Calibration Factor mode, nn.nn is the Cal
Factor in dB.
9. If a coupler or attenuator is being used at the detector input, enter the attenuation value as a
positive offset. For example, if an attenuator with a value of 30.2 dB at the frequency of
2-18 Manual No. 20790, Rev C, November 1998
Superceded by Revision D, March 2009