Calibration - Wavetek 39A Maintenance Manual

All parameters can be calibrated without opening the case, i.e. the generator offers 'closed−box'
calibration. All adjustments are made digitally with calibration constants stored in EEPROM. The
calibration routine requires only a DVM and a frequency counter and takes no more than a few
minutes.
The crystal in the timebase is pre−aged but a further ageing of up to ±5ppm can occur in the first
year. Since the ageing rate decreases exponentially with time it is an advantage to recalibrate
after the first 6 month's use. Apart from this it is unlikely that any other parameters will need
adjustment.
Calibration should be carried out only after the generator has been operating for at least 30
minutes in normal ambient conditions.
Equipment Required
• 3½ digit DVM with 0.25% DC accuracy and 0.5% AC accuracy at 1kHz.
• Frequency counter capable of measuring 10.00000MHz.
The DVM is connected to the MAIN OUT of each channel in turn and the counter to any SYNC
OUT.
Frequency meter accuracy will determine the accuracy of the generator's clock setting and
should ideally be ±1ppm.
Calibration Procedure
The calibration procedure is accessed by pressing the calibration... soft−key on the
UTILITY screen.
The software provides for a 4−digit password in the range 0000 to 9999 to be used to access the
calibration procedure. If the password is left at the factory default of 0000 no messages are
shown and calibration can proceed as described in the Calibration Routine section; only if a
non−zero password has been set will the user be prompted to enter the password.
Setting the Password
On opening the Calibration screen press the password
screen:
Enter a 4−digit password from the keyboard; the display will show the message NEW PASSWORD
STORED! for two seconds and then revert to the UTILITY menu. If any keys other than 0−9
are pressed while entering the password the message ILLEGAL PASSWORD!
Using the Password to Access Calibration or Change the Password
With the password set, pressing calibration... on the UTILITY
18
CALIBRATION SELECTED
Are you sure ?
◊password... tests...◊
◊exit continue◊
ENTER NEW PASSWORD
−−−−
ENTER PASSWORD
----

Calibration

... soft−key to show the password
screen will now show:
will be shown.