Fluke PM6690, Service Manual, Page: 15 / 200

– Press
INPUT A
and select
MAN
ual trigger level and
50
W
input impedance.
– Connect the LF synthesizer to Input A. Use the follow-
ing settings (into 50
W
):
Sine, 10 kHz, 0.9 V
PP
, and +0.50 V
DC
.
– Verify that the three modes for the trigger indicator are
working properly by changing the trigger level:
– Press the
Trig
key and enter +1 V via the keyboard,
then verify by pressing
EXIT/OK.
Check the trigger
indicator according to Table 2-4.
– Press the
Trig
key and enter –1 V via the keyboard
by pressing the
±
key, then verify by pressing
EXIT/OK
. Check the trigger indicator according to
Table 2-4.
–
Press the Trig key and enter 0 via the keyboard, then
verify by pressing EXIT/OK . Check the trigger indica-
tor according to Table 2-4.
– Apply the signal to Input B instead.
– Press
MEAS FUNC
®
Freq
®
Freq (A)
®
B
– Press
INPUT B
and select
MAN
ual trigger level and
50
W
input impedance..
– Repeat the trigger level settings above to verify the three
trigger indicator modes for Input B.
Input Controls
– Recall the DEFAULT settings.
– Connect the LF synthesizer to Input A. Use the same
settings as in the previous test.
– Press INPUT A and select DC and 50
W
.
– Press
EXIT/OK
.
– Check the V
max
and V
min
voltage levels on the display
according to the first row in Table 2-6.
– Perform the rest of the settings in sequence, and read the
corresponding V
max
and V
min
values. Remember that all
these values are approximate and serve only as indica-
tors of state changes.
– Connect the generator to Input B.
– Press
MEAS FUNC
®
Freq
®
Freq (A)
®
B
– Press
INPUT B
and select
DC
and
50
W
.
– Press
EXIT/OK
.
– Check the V
max
and V
min
voltage levels on the display
according to the first row in Table 2-6.
– Perform the rest of the settings in sequence, and read the
corresponding V
max
and V
min
values.
Reference Oscillators
X-tal oscillators are affected by a number of external condi-
tions like ambient temperature and supply voltage. Aging is
also an important factor. Therefore it is hard to give limits for
the allowed frequency deviation. The user himself must de-
cide the limits depending on his application, and recalibrate
the oscillator accordingly.
To check the accuracy of the oscillator you must have a cali-
brated reference signal that is at least five times more stable
than the oscillator that you are testing. See Table 2-7 and the
list of test equipment on page 2-2. If you use a non-10 MHz
reference, you can use the mathematics in the timer/counter to
multiply the reading.
– Recall the DEFAULT settings. See page 2-2
– Connect the reference to input A
– Check the readout against the accuracy requirements of
your application.
n
Acceptance Test
Table 2-7 can serve as an acceptance test and gives a worst
case figure after 30 minutes warm-up time. All deviations that
can occur in a year are added together.
Resolution Test
– Connect the pulse generator to a power splitter.
– Connect one side of the power splitter to Input A on the
counter using a coaxial cable.
– Connect the other side of the power splitter to Input B
on the counter.
Settings for the pulse generator:
– Amplitude = 2 V
PP
, (high level +2V and low level 0 V)
– Period = approx. 1
m
s
– Duration = approx. 50 ns
– Rise time = 2 ns
Restore the timer/counter's default settings and make the fol-
lowing changes:
– Function =
Time A-B
– Press
STAT/PLOT
key to the right of the display.
– Settings for INPUT A and INPUT B :
50
W
input impedance
MAN
ual trigger level
Performance Check, Short Form Specification Test 2-5
Settings V
max
V
min
Pass/Fail
Input A Input B
INPUT A, DC, 50
W
+950 mV
+50 mV
AC
+450 mV
-450 mV
10X
+0.45 V
-0.45 V
1 M
W
>+0.45 V
<-0.45 V
Table 2-6
Input controls check.
Oscillator Frequency Readout Suitable
Reference
P/F
Standard
(PM6690/_1_)
10.00000000 MHz
±
150 Hz 908
OCXO
(PM6690/_5_)
10.00000000 MHz
±
1 Hz 909
OCXO
(PM6690/_6_)
10.00000000 MHz
±
0.25 Hz 909
Table 2-7
Acceptance test for oscillators.