Calibration
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 Flash. The
calibration routine requires only a DVM, an oscilloscope 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 20·00000MHz.
•
An oscilloscope for the Symmetry adjustment (CAL 13 & CAL14).
The DVM is connected to the MAIN OUT and the counter to the AUX 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
calibrate
...
soft
−
key on the
UTILITIES
screen.
CALIBRATION SELECTED
Are you sure ?
◊
password… tests…
◊
◊
exit continue
◊
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
...
soft
−
key to show the password
screen:
ENTER NEW PASSWORD
----
Enter a 4
−
digit password from the keyboard; the display will show
CONFIRM NEW
PASSWORD
.
Re-enter the password; the display will show the message
NEW
PASSWORD STORED!
for two
seconds and then revert to the
UTILITIES
menu. If any keys other than 0
−
9 are pressed while
entering the password, or if the password is re-entered incorrectly, the message
ILLEGAL
PASSWORD!
will be shown.
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