performance of in-hull transducers in fiberglass hulls hull frequency... · •performance of...
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Performance of In-Hull Transducers in Fiberglass Hulls
In-Hull Transducers and Fiberglass Hull Thickness
•Performance of in-hull transducers like the M260 and R199 varies with hull thickness and operating frequency. There is no maximum allowable hull thickness.
•The optimum combination of hull thickness and operating frequency offers deeper target detection. The difference in depth detection can be up to 11% at 50 kHz and 7% at 200 kHz.
• Alternately, for a given hull thickness there will be one or more optimum operating frequencies to achieve maximum target detection.
• Broadband transducers offer the capability of tuning the sonar frequency to minimize transmission losses through the hull
• A sounder, using a broadband transducer, could be programmed to perform automatic tuning to find the optimum frequencies.
In-Hull Transducers and Fiberglass Hull Thickness
Transmission losses through the hull are due to two factors:
1. Absorption of the ultrasonic energy by the fiberglass hull. The thicker the hull, the greater the absorption.
2. “Impedance mismatch”:the thickness of the hull in wavelengths at the operating frequencies can cause transmission loss and shift the transducer frequency
– For hull thicknesses of 1/4, 3/4, 5/4, etc…, hull losses due to impedance mismatch will be lowest
– For hull thicknesses of 1/2, 1 and 1.5 wavelengths, losses will be highest.
– For a hull thickness (in wavelengths) that is not 1/4, 3/4, 5/4, etc…, the operating frequency of the transducer will be shifted.
In-Hull Transducers and Fiberglass Hull Thickness
M260 Specifications No Fiberglass
50 kHz 200 kHz
The following graphs show the loss and frequency shift when an in-hull transducer is transmitting through:
• No Fiberglass• 3/8” Fiberglass• 1/2” Fiberglass• 3/4” Fiberglass• 1” Fiberglass
• Note: In Hull transducers will not work with cored fiberglass, wood, or aluminum hulls due to excessive signal loss.
In-Hull Transducers and Fiberglass Hull Thickness
155
156
157
158
159
160
161
162
163
164
0" FIBERGLASS 3/8" FIBERGLASS 1/2" FIBERGLASS 3/4" FIBERGLASS 1" FIBERGLASS
HULL THICKNESS
TVR
(dB
)
0% Loss in Range
10% Loss in Range
5% Loss in Range
3% Loss in Range
7% Loss in Range
M260 50 kHz TVR CHANGE(RANGE LOSS)vs. HULL THICKNESS
40
42
44
46
48
50
52
54
56
0" FIBERGLASS 3/8" FIBERGLASS 1/2" FIBERGLASS 3/4" FIBERGLASS 1" FIBERGLASS
HULL THICKNESS
kHz
M260 50 kHz FREQUENCY SHIFTvs. HULL THICKNESS
50 kHz
53.5 kHz
51 kHz
53 kHz
45.5 kHz
M260 Max depth @ 50 kHz 1kW Input power
• No fiberglass- 3333’ (1015m)• 3/8” fiberglass- 3100’ (944m)• ½” fiberglass- 2850’ (868m)• ¾” fiberglass- 3190’ (972m)• 1” fiberglass- 3000’ (914m)
164
165
166
167
168
169
170
171
172
0" FIBERGLASS 3/8" FIBERGLASS 1/2" FIBERGLASS 3/4" FIBERGLASS 1" FIBERGLASS
HULL THICKNESS
TVR
, (dB
)
7% Loss in Range
3% Loss in Range
5% Loss in Range
4% Loss in Range
0% Loss in Range
M260 200 kHz TVR CHANGE & RANGE LOSSvs. HULL THICKNESS
M260 200 kHz FREQUENCY SHIFT vs. HULL THICKNESS
180
185
190
195
200
205
210
215
0" FIBERGLASS 3/8" FIBERGLASS 1/2" FIBERGLASS 3/4" FIBERGLASS 1" FIBERGLASS
HULL THICKNESS
kHz
200 kHz
210 kHz
190 kHz
210 kHz
191 kHz
M260 Max depth @ 200 kHz 1kW Input Power • No fiberglass- 1305’ (397m)• 3/8” fiberglass- 1165’(355m) • ½” fiberglass- 1255’ (382m) • ¾” fiberglass- 1200’ (365m) • 1” fiberglass- 1225’ (373m)
50kHz Maximum Depth RangeM260 In-Hull - 1kW Input Power
500 1000 1500 2000 2500 3000 3500 4000
0
20
40
60
80
100
120
Depth, feet
Sig
nal E
xces
s, d
B
50 k Hz Thru Hull Range B ehavior
no hull3/8" hull1/2" hull3/4" hull1" hull+ 6 dB detec tion thres hold
Area of Detail – (Next Slide)
Maximum Depth Line
Maximum Depth Line
50 kHz Maximum Depth RangeM260 In-Hull - 1kW Input Power
Depending on hull thickness,340 feet of depth sensing(11%) can be gained (or lost)
Maximum Depth Line
200 kHz Maximum Depth RangeM260 In-Hull - 1kW Input Power
200 400 600 800 1000 1200 1400 16000
20
40
60
80
100
120
Depth, feet
Sig
nal E
xces
s, d
B
200 k Hz Thru Hull Range B ehavior
no hull3/8" hull1/2" hull3/4" hull1" hull+ 6 dB detec t ion thres hold
Area of Detail – (Next Slide)
Maximum Depth Line
Maximum Depth Line
200 kHz Maximum Depth RangeM260 In-Hull - 1kW Input Power
Depending on hull thickness,90 feet of depth sensing (7%) can be gained (or lost)
Maximum Depth Line
R199 2kW Specifications No Fiberglass
50 kHz 200 kHz
200kHz Q = 2 200kHz Q = 4.5No Fiberglass ¾” Fiberglass
Flat response: any frequency between 160 to 240 kHz is an efficient operating frequency
Transmitting through the hull reduces bandwidth and shifts frequency - 180 kHz is now
the best operating frequency
R199 2kW @ 200 kHz
50kHz Q = 3 50kHz Q = 4.1No Fiberglass ¾” Fiberglass
Flat response: any frequency between 46 to 55 kHz is an
efficient operating frequency
Transmitting through the hull reduces bandwidth and shifts
frequency - 43 kHz is now the best operating frequency
R199 2kW @ 50 kHz
• On the high frequency ceramic, the best resonant frequency has shifted to 180 kHz. The bandwidth of the transducer installation is reduced.
• Stated another way, 180 kHz is the best operating frequency. While 200 kHz operation will work well, there will be an 11% loss in range.
• On the low frequency ceramic, the best resonant frequency has shifted to 43 kHz. The bandwidth of the transducer installation is reduced.
• For a 3/4” thick hull, 43 kHz is the best operating frequency. Operating at 50 kHz will result in a range loss of 7%
R199 2kW Summary