Calibration - Hameg Instruments HM8021-4 Manual

C a l i b r a t i o n
is low, the counter makes all necessary prepa-
rations for a measurement. With the high level
of the gate signal, measurement starts when the
input signal triggers after a synchronization delay.
Measurement stops on the first trigger after the
gate signal changes from high to low. The external
gate overrides the set measurement time. The
external gate signal must be in the range 100ns
... 10sec. but the effective gate time will never be
smaller than 150 μs.
after the gate signal changes from high to low.
External gate is selected by means of the pushbut-
The external gate overrides the set measurement
and indicated by means of LED. External
ton
time. The external gate signal must be in the
gate can be used in all functions.
range 100ns ... 10sec. but the effective gate time
Example applications are multiple burst fre-
will never be smaller than 150 µs.
quencies and masked time intervals. Note that
External gate is selected by means of the
if RF bursts are to be measured using frequency
pushbutton [3] and indicated by means of LED.
C, the burst should contain at least 128 cycles of
External gate can be used in all functions.
the f requency to be measured. External gating is
Example applications are multiple burst fre-
active according to the level applied to the input
quencies and masked time intervals. Note that if
(rear side of mainframe).
RF bursts are to be measured using frequency C,
the burst should contain at least 128 cycles of the
f requency to be measured. External gating is
active according to the level applied to the input
(rear side of mainframe).

Calibration

Caution! The time-base of the HM 8021-4 unit
should only be re-aligned, if a high-precision
frequency standard is available.
Crystal oscillators are subject to natural aging
during operation, which leads to deviations from
their basic accuracy. Therefore they should be re-
aligned at least twice peryear to ensure the
accuracy indicated in the specification.
If recallibration is necessary it is carried out as
follows:
1) Select function FA (Frequ.A), OFFSET and
DISPLAY HOLD should be in OFF position.
24
Subject to change without notice
2) Apply a frequency standard of 1,5 or 10MHz
Calibration
Crystal oscillators are subject to natural aging
during operation, which leads to deviations from
their basic accuracy. Therefore they should be
re-aligned at least twice peryear to ensure the
accuracy indicated in the specification.
Caution!
5) When the switches are released the display
The time base of the HM 8021-4 unit should only
shows the date of the last recalibration (DD-
be realigned, if a high-precision frequency stan-
MM-YY or 00-00-00).
dard is available.
If recallibration is necessary it is carried out as
6) You may leave calibration mode by
follows:
depressing RESET T. In this case no changes
are made and the unit is working in normal
1) Select function FA (Frequ.A), oFFSET and
DISPLAY HoLD should be in oFF position.
mode.
2) Apply a frequency standard of 1, 5 or 10 MHz
7) If you want to change the date of the last
to input A and adjust channel A trigger setting
calibration youshouidproceedfromste 5:
for a stable reading.
Using the key ← or → (left or right function
shift keys) you can choose the digit that has
3) Depress RESET
to be changed (not flashing). The different
for approx. 5secs.
digits are changed by pushing down the
GATE TIME [3] key several times. When the
4) The display shows "A...o" during the push
last digit is corrected (now the last digit
buttons are depressed.
should light brightly e.g. 20-02-89) you can
leave the calibration procedure (continue with
5) When the switches are released the display
step 7a) or frequency calibration can be
shows the date of the last recalibration (DD-
performed (continue with step 7b).
MM-YY or 00-00-00).
7a) If you only want to store the date of the last
6) You may leave calibration mode by depressing
calibration without changing the timebase
RESET. In this case no changes are made and
calibration, there should not be any signal at
the unit is working in normal mode.
the input A during the following steps. After
depressing the right function key "A..."
7) If you want to change the date of the last cali-
will be indicated in the display after a few
bration youshouidproceedfromste 5:
seconds. If you now depress the reset button
Using the key Å or Æ (left or right function shift
you are again in the normal mode.
keys) you can choose the digit that has to be
changed (not flashing). The different digits are
7b) If there is a standard frequencyof 1, 5 or
changed by pushing down the GATE TIME
10MHz at the input A, depress the right
key several times. When the last digit is cor-
function shift key. A few seconds later the
rected (now the last digit should light brightly
display shows following informations:
e.g. 20-02-89) you can leave the calibration
A... if the standard frequency applied is not procedure (continue with step 7a) or frequency
accepted calibration can be performed (continue with
step 7b).
A... 1 6 if the counter has recognized a
1 MHz standard
7a) If you only want to store the date of the last
A... 5 6 if the counter has recognized a
calibration without changing the timebase
5 MHz standard
calibration, there should not be any signal at
A... 10 6 if the counter has recognized a
10 MHz standard
During the following 45 seconds the signal is
and then GATE TIME