Fusible Metal Film
Resistors
FA8025 series
Welwyn Components
•
Predictable fusing characteristics
•
Flameproof protection
Electrical Data
FA8225
Power rating at 70˚ C
Resistance range
Limiting element voltage
TCR
Resistance tolerance
Standard values
Thermal impedance
Ambient temperature range
˚ C/watt
˚C
150
watts
ohms
volts
ppm/˚ C
%
0.25
0R1 - 10k
250
250
FA8325
0.5
0R1 - 27k
350
250
5
E24 preferred
120
-55 to 155
90
FA8425
1.5
0R15 - 22k
500
250
Physical Data
Dimensions (mm) & Weight (g)
PCB
Type
FA8225
FA8325
FA8425
L max
6.2
9.0
14.5
D max
2.5
2.3
3.4
5.1
f min
21
19.6
23.8
d nom
0.6
0.8
0.8
mounting
centres
10.2
12.7
20.3
Min.
bend
radius
0.6
1.2
1.2
Wt. nom
0.3
0.6
1.1
d dia
D
L
f
Construction
The metal film is deposited on a high purity ceramic rod. End
caps are force fitted and termination wires welded to the
caps. The resistive film is adjusted to the required value by a
helical cut; finally the cement protection is applied to the
resistor body and marked with indelible ink.
Marking
Resistors are colour coded with five bands. Four of the bands
are used to indicate value and tolerance, with IEC 62 colours
being used. On FA8325 and FA8425 types a fifth yellow band
denotes constant voltage fusibility.
Solvent Resistance
Terminations
Material
Strength
Solder-coated copper wire.
The terminations meet the requirements of
IEC 68.2.21.
The body protection and marking are resistant to all normal
industrial cleaning solvents suitable for printed circuits.
Flammability
The resistors will not burn or emit incandescent particles
under any condition of applied temperature or power
overload.
Solderability
The terminations meet the requirements of
IEC 115-1, Clause 4.17.3.2.
General Note
Welwyn Components reserves the right to make changes in product specification without notice or liability.
All information is subject to Welwyn’s own data and is considered accurate at time of going to print.
A subsidiary of
TT electronics plc
Issue C · 01.07
B 03.02
© Welwyn Components Limited
· Bedlington, Northumberland NE22 7AA, UK
Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: info@welwyn-tt.com · Website: www.welwyn-tt.com
153
Fusible Metal Film
Resistors
FA8025 series
Welwyn Components
Performance Data
Maximum
Load: 1000 hours at 70˚C
Shelf life: 12 months at room temperature
Derating from rated power at 70˚ C
Temperature rapid change
Resistance to solder heat
R%
R%
0.5
0.5
R%
R%
2
0.5
zero at 155˚ C
0.2
0.2
Typical
0.5
0.2
Predicting Fusing Time For Defined Power Input
Graphs 1 to 3.
Fusible Resistors: Typical Fusing Window
Graph 4.
Normal rated
power
Fusing:
After fusing the final resistance value will be 50 times the
initial value. See graph for explanation of fusing curves.
Graph 1
Fusing
Time
(secs)
Min power for
guaranteed
fusing
Max fusing time
Min fusing time
Initial Power (watts)
Max sale
fusing
power
Packaging
The preferred method of packaging is taped and ammo
packed, see figure 1 for critical dimensions.
Alternative packaging is available by special request.
Graph 2
Lead Formed resistors can also be supplied. Standard options
of Lancet, Radial and Goalpost forming are shown in Lead
Form Information section.
Figure 1
c
f
1
Graph 3
6
b
Body Location f
1
– f
2
f
2
6
1.4 mm
Type
b
c
FA82*
26
5
FA82/FA83
52
5
FA84
67
10
Standard Quantities Per Package
Type
Ammopack
FA8225
5000
FA8325
2500
FA8425
1000
© Welwyn Components Limited
Bedlington, Northumberland NE22 7AA, UK
Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: info@welwyn-tt.com · Website: www.welwyn-tt.com
154
Issue C · 03.02
B 01.07
MicroPython Open Source section
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