Checking Resonant Frequency Characteristic - Furuno FCV-1200L Service Manual

Table 7.1 Ro: matching impedance
Freq. Power Type
15 kHz 1 kw 15F-4S
2 kw 15F-10
3 kw 15F-10X2
28 kHz 1 kw 28F-8
2 kw 28F-18
3 kw 28F-24H
45 kHz 1 kw 45F-3H
2 kw 45F-6H
3 kw 45F-12H
50 kHz 1 kw 50B-6/6B
50B-8G
50F-9B
2 kw 50B-12
3 kw 50F-24H

7.3 Checking resonant frequency characteristic

Procedure 1 : using the impedance check circuit shown in figure 7.1.
Make an impedance check circuit as shown in figure 7.1 and measure the resistance at various
frequencies. Plot the measured resistance vs. frequency.
The typical curve is shown in figure 7.2.
Impedance
Figure 7.2 Resonant characteristic curve : Frequency vs. Impedance
To check the transducer whether it is good or not, compare the curve with one obtained from a good
transducer.
If the transducer is defective, impedance curve differs form that of the normal transducer.
•
When transducer elements peel off the housing, the ratio of A to B increases. This is similar to
the measurement in air.
•
When transducer element is cracked, several other resonant points may be obtained.
•
When transducer element split up, resonant point may be not obtained at the frequency "Fo".
Ω Ω
Z( ) Ro( )
16 + j31 78
23 + j69 233
7.2 + j34.5 173
18 + j68 274
35 + j64 152
100 + j0 100
100 + j0 100
100 + j0 100
100 + j0 100
190 - j165 333
100 + j0 100
95 - j90 180
119 - j152 320
100 + j0 100
B
A
Fo Fr
Table 7.2 Ro: matching impedance
Freq. Power
68 kHz 1 kw
3 kw
88 kHz 1 kw
2 kw
3 kw
100 kHz 3 kw
150 kHz 3 kw
200 kHz 1 kw
2 kw
3 kw
400 kHz 1 kw
Fo: Resonant frequency
Fr: Reverse resonant point
Frequency
39
Ω
Type
Z( )
68F-8H 100 + j
68F-30H 100 + j0
88B-8 318 - j342
88B-10 229 - j140
88F-126H 100 + j0
100B-10R 198 + j248
150B-12H 100 + j0
200B-5S 246 - j282
200B-8 98 - j87
200B-8B 95 - j82
200B-8N 115 - j2
200B-12H 100 + j0
400B-52 49 - j53
Ω
Ro( )
100
100
709
321
100
509
100
575
177
169
116
100
106