Mini Melf
Resistors
WRM Series
Welwyn Components
•
High reliability
•
Predictable pulse handling capability
•
Tolerances down to 0.1%
•
TCR down to 5 ppm/°C
Electrical Data
WRM 0102
Power rating at 70°C
Resistance range
Limiting element voltage
TCR
Resistance tolerance
Standard values
Thermal impedance
Ambient temperature range
Insulation resistance
k/W
°C
ohms
250
watts
ohms
volts
ppm/°C
%
0.2
R22 – 2M21
150
15, 25, 50
WRM 0204
0.25
R22 – 10M
200
5, 15, 25, 50
0.1, 0.25, 0.5, 1.0, 2, 5
E24 & E96
200
-55 to +125
>10
10
140
WRM 0207
0.4
R22 – 8M2
250
25, 50
Physical Data
Dimensions (mm) and weight (g)
Type
WRM 0102
WRM 0204
WRM 0207
L
max
2.2
3.7
6.1
D
max
1.1
1.55
2.4
D
1
max
1.1
1.55
2.4
K
min
0.35
0.5
0.5
Weight
0.01
0.02
0.08
L
D
1
L
1
K
D
Construction
A metal film is deposited onto a high dissipation ceramic
former to which tin plated teminating caps are fitted.
The resistor is adjusted to value by a helical cut in the film
and the body is protected by a lacquer coating.
Terminations
Material
Plated steel cap.
Solderability
The pure tin finish produces ageing free
contacts on which low melting solders can
be used. Dipped area shall be covered with
a smooth and bright solder coating after
3 seconds immersion at 215°C.
Marking
Resistance values are colour coded with 4 or 5 bands
depending on type.
Solvent Resistance
The body protection and marking are resistant to all normal
industrial cleaning solvents suitable for printed circuit boards.
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 D · 09.06
© 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
Mini Melf
Resistors
WRM Series
Welwyn Components
TCR and Tolerance Range
Type
Reference
5%
WRM0102
WRM0102
WRM0102
WRM0102
WRM0102
WRM0204
WRM0204
WRM0204
WRM0204
WRM0204
WRM0207
WRM0207
WRM0207
WRM0207
WRM0207
±50ppm
±25ppm
±15ppm
±10ppm
±05ppm
±50ppm
±25ppm
±15ppm
±10ppm
±05ppm
±50ppm
±25ppm
±15ppm
±10ppm
±05ppm
R22 – R91
–
–
–
–
R22 – R91
–
–
–
–
R22 – R91
–
–
–
–
2%
IRO – 9R1
–
–
–
–
–
–
–
–
–
–
–
–
–
–
1.0%
10R – 2.21M
10R – 221K
–
–
–
1R – 10M
10R – 475K
–
–
–
1R – 8.2M
–
–
–
–
0.5%
47RS – 221K
47R5 – 221K
100R – 100K
–
–
10R – 475K
10R – 475K
10R – 221K
–
–
10R – 1M
10R – 1M
–
–
–
0.25%
100R – 221K
100R – 221K
100R – 100K
–
–
22R – 332K
22R – 332K
22R – 221K
22R – 221K
100R – 100K
–
–
–
–
–
0.1%
–
100R – 100K
100R – 100K
–
–
43R – 332K
43R – 332K
43R – 221K
43R – 221K
100R – 100K
–
–
–
–
–
TCR
Tolerance
* TC 10ppm & 5ppm is specified over the temperature range -10°C to +85°C.
Performance Data
Test
Description
0.25
75
Ω
– <100 kΩ
Short time overload*
Bending test*
Resistance to soldering heat
Temperature rapid change
Endurance*
Load life
Climatic sequence*
Damp heat steady state*
Current noise
Solderability
Voltage coefficient
Voltage proof
1000h
8000 h
≤
0.25% + 0.05
Ω
≤
0.5% + 0.05
Ω
≤
0.25% + 0.05
Ω
≤
0.25% + 0.05
Ω
< 0.05 µV/V
≤
0.25% + 0.05
Ω
≤
0.5% + 0.05
Ω
≤
0.5% + 0.05
Ω
≤
0.5% + 0.05
Ω
< 0.25 µV/V
Dipped area shall be covered with a smooth
and bright solder coating of at least 96%
< 0.5 . 10
6
/V
No flashover or breakdown
≤
0.5% + 0.05
Ω
≤
1.0% + 0.05
Ω
≤
1.0% + 0.05
Ω
≤
1.0% + 0.05
Ω
< 3 µV/V
≤
0.05% + 0.01
Ω
≤
0.05% + 0.01
Ω
≤
0.05% + 0.01
Ω
≤
0.05% + 0.01
Ω
Results
∆
R/R ±
Stability class
0.5
10
Ω
– <75
Ω
>100 kΩ – 332 kΩ
≤
0.1% + 0.01
Ω
≤
0.1% + 0.01
Ω
≤
0.1% + 0.01
Ω
≤
0.1% + 0.01
Ω
1.0
0.22
Ω
– <10
Ω
>332 kΩ – 10 MΩ
≤
0.25% + 0.05
Ω
≤
0.25% + 0.05
Ω
≤
0.25% + 0.05
Ω
≤
0.25% + 0.05
Ω
* Resistors to be mounted on a PC-board according to IEC 115-1, clause 4.27.1
© 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
Issue D · 09.06
Mini Melf
Resistors
WRM Series
Single Pulse
Maximum Pulse Load
WRM 0102
WRM 0204
WRM 0207
Welwyn Components
100
Pulse Load
P
max
W
10
1
0,1
10
µs
100
µs
1 ms
10 ms
100 ms
1s
10 s
Pulse Duration
t
i
Continuous Pulses
Maximum Pulse Load
Continuous Pulse Load
P
max
WRM 0102
WRM 0204
WRM 0207
100
W
10
1
0,1
10
µs
100
µs
1 ms
10 ms
100 ms
1s
10 s
Pulse Duration
t
i
Packaging
The WRM 0102 and 0204 resistors are supplied reeled on 8mm blister tape.
WRM 0207 resistors are supplied on 12mm blister tape.
Packaging complies with the requirements of IEC 286-3.
Ordering Procedure
Example: WRM0204 at 1 kilohm, 1% tolerance and 50ppm/ºC TCR on a reel of 3000 pieces -
Type
Size
TCR
C 50ppm/ºC
D 25ppm/ºC
Y
15ppm/ºC
T
V
10ppm/ºC
5ppm/ºC
I
Tape
0102
0204
0207
3000 / reel (7”)
3000 / reel (7”)*
1500 / reel (7”)
Standard
WRM
0204
C -
1K0
F
I
Packing
* High precision parts may be supplied on 1000 piece reels – please enquire
Value (use IEC62 code)
Tolerance (use IEC62 code)
B
0.1%
D
0.5%
1%
G 2%
J
5%
C 0.25% F
© 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
Issue D · 09.06
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