NOTE: When recalibrating, the reference crystal
oscillator
will be compensated only for frequency
deviation
caused by aging.
Model
Options
stability
against
/.I.
1.2.
/.4.
1.5.
PM
9678B PM 9690
PM
9691
Standard
TCXO
Oven
Oven
Aging:
/24h
n.a.
n.a.
<1
^=10"^*
<5
10"'^°*
Aging:
/month
<5
*
10'^
<1
*
10’’'
<2
*
10“®
<1
*
10'®
Aging: /year
<5
*
10-®
<5
10'^
<1
10'^
<7.5*
10'®
Temperature:
0 to 50°C ref. to
+
23°C
A
O
tn
<1
*
10'®
<1.5
*
10'®
<5
*
10'®
Line Voltage
+
10%
<1
*
10“®
<1
10"^
<5 *
10"''°
<5
*
IC'’®
Warm-up Time
to Reach
10'^
of
Final Value
n.a.
n.a.
<
15
min
<
15 min
Table
5-1
*
after
48 hours of continuous operation
Battery Replacement
To
preserve data
and variables needed for the use of
PM
6681 a lithium battery
is included. The
lithium
battery
has an estimated lifetime of five to ten years. We recom-
mend an replaceing the
battery every five years
to avoid
loss of data in operation.
When battery Is empty, the timer/counter will lose all set-
tings, and any data in memory, if disconnected from line
power.
See "Reinstalling the Battery" on page
3-4.
Calibration interval
I
+
Standard PM 9678B
+
PM
9690
^
PM
9691
Figure
5-3
MTBRC in years.
Preventive Maintenance
5-3
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