TB 9-6625-2188-24
Example:
-112.2
-108.0
4.2 = difference value
(12) Locate difference value (4.2) in table 7 below and determine corresponding
additive factor (1.42). Algebraically add additive factor to the numerically lower dB value
(2d harmonic) of (10) above.
Example:
-108.0
1.42
-106.58 = resulting number
Table 7. Factors for THD Computation
Difference
Additive
Difference
Additive
values
factors
values
factors
0.0
3.01
10.0
0.41
0.5
2.77
11.0
0.33
1.0
2.54
12.0
0.27
2.0
2.12
13.0
0.21
3.0
1.76
14.0
0.17
4.0
1.46
15.0
0.14
5.0
1.19
16.0
0.11
6.0
0.97
17.0
0.09
7.0
0.79
18.0
0.07
8.0
0.64
19.0
0.05
9.0
0.51
20.0
0.04
(13) Repeat technique above using resulting number from (12) above and the next
numerically lower dB value (4th harmonic) of (10) above.
Example:
-120.0
-106.58
13.42 = difference value
(14) Locate difference value (13.42) in table 7 and determine corresponding additive
factor (0.20). Algebraically add additive factor to resulting number of 12 above.
Example:
-106.58
.20
-106.38 = resulting number
(15) Compute arithmetic difference between the remaining dB value (5th harmonic)
of (10) above and resulting number of (14) above.