Service manual

16 Agilent 382A Operating and Service Manual
Operation
8. Read SWR meter and determine attenuation change from reference
reading. Subtract the calibration value. The remainder (with the
appropriate sign) is the true value of the SWR meter 10 dB range
attenuation. Record this value and use it as the corrected reference point
for all measurements at this frequency.
Calibrate 382A
The 382A can now be accurately calibrated since the error in the system is
known. Proceed as follows:
1. Remove the directional coupler used as a standard and replace it with the
382A under test set to 0 dB.
2. Set SWR meter to 40 dB and set to a reference point at the mid-scale on
one of the expanded scales. The variable attenuator remains set at 41 dB
as in the previous procedure.
3. Increase dial setting of 382A under test exactly 10 dB and set SWR
meter to 50 dB gain.
4. Read the error considering the range switching error determined in the
previous procedure. Error (between steps or cumulative) must not be
greater than ±(0. 2 dB - mismatch error).
5. Set SWR meter to 40 dB gain and variable attenuator to roughly 31 dB.
Set a reference on an expanded scale as previously, taking into account
the cumulative error. Repeat steps 3 and 4.
6. Set SWR meter to 40 dB gain and variable attenuator to roughly 41 dB.
Set reference on an expanded scale as previously, taking into account the
cumulative error. Repeat steps 3 and 4.
7. Set SWR meter to 40 dB gain and variable attenuator to roughly 51 dB.
Set reference on an expanded scale as previously, taking into account the
cumulative error. Repeat steps 3 and 4.
8. Repeat the processes for all calibrated frequencies of the directional
coupler standard. Apply calibration corrections to the results obtained.
This procedure tests the 382A with the maximum accuracy. However, if a
calibrated coupler is not available or if a simpler procedure is desired, the
382A may be calibrated directly against an SWR meter. This method has
additional errors due to not being referred to a standard, having cumulative
errors due to the SWR meter attenuator, and due to the non-linearity of the
crystal but may be used as a rough check.