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4.5
Measurement modes
4.5.1
"Two-oscillators, one-channel" mode
For any number of channels (one to eight) measured and reference signals (from
the inputs “
fy” and “
fx“ respectively) are involved in the measurements (see
Figure 5) for each of the channels. The measuring program calculates the relative
frequency difference and frequency instability of both signals and the channel itself.
Table 3 shows available functions and corresponding mathematical expectation
for the measuring channel CHANNEL 1 calculated on the assumption that frequency
fluctuations of all signals and measuring channel are independent.
Table 3 – Available functions for "two oscillators, one-channel" mode
Number
Calculated function
Mathematical expectation
1
Relative frequency difference
measured for CHANNEL 1
N
c
N
x
N
y
y
y
y
1
1
1
+
−
2
Standard deviation
measured for CHANNEL 1
2
1
2
1
2
1
c
x
y
+
+
3
Allan deviation
measured for CHANNEL 1
2
1
2
1
2
1
c
x
y
+
+
where:
N
x
N
y
y
y
1
1
,
– the average value of the relative frequency difference of "
fx" and
"
fy" input
signals on averaging interval
N·
;
N
c
y
1
– mean frequency difference introduced by the measuring channel
CHANNEL 1;
2
1
2
1
2
1
,
,
c
x
y
– N-sample variance of "
fx" and "
fy" input signals and the
measuring channel CHANNEL 1;
