For technical questions, contact: powertron@vishaypg.com
USR UNR 4-3425 3825 4020
Powertron
Document Number: 64223
Revision: 20-09-10
www.powertron.de
1
Type USR 4-
3425 3825
USR 4-
4020
UNR 4-
3425 3825
UNR 4-
4020
Resistance Range 0.05 to 500 Ohms 0.05 to 400 Ohms
other resistance values upon request / power rating depending on resistance value
Power rating
free air 70°C
for 3825H
with heatsink
3 W
5 W
30 W
2.5 W
30 W
3 W
5 W
50 W
2.5 W
50 W
Thermal Resistance Rthj-c 3.5 K/W 3.6 K/W 2.1 K/W 2.2 K/W
Tolerances
from 0.05 Ohms
from 10.0 Ohms
from 50.0 Ohms
0.1% / 0.25% / 0.5% / 1%
0.05% / 0.1% / 0.25% / 0.5% / 1%
0.01% / 0.02% / 0.05% / 0.1% / 0.25% / 0.5% / 1%
Stability 0.01%
Shelf Life Stability 25ppm / ∆R after 1 year
50ppm / ∆R after 3 year
Temperature Coefcient max. ±5ppm/K (-55 to 155°C)
typ. ±3ppm/K (-55 to 125°C)
upon request ±1ppm/K (0 to 60°C)
Voltage Proof 750 VDC
max. Current 15 A
Thermal EMF < 0.1µV/K
Operating Temperature Range -55 to 155°C
Resistor Material NiCr-Foil
Substrate Al2O3AlN
Housing Epoxy + Al-heatsink
Connector Material Cu tinned
Terminals 4
Max. Torque 1.0 Nm
Notes Specially designed for applications with fast
changing electrical load
SPECIFICATIONS
Part Number - Resistance - Contact - Tolerance - TCR
USR 4-3825H 10Ohms D 0.5% 3ppm
Ordering Information
Resistances from 0.05Ohm to 500Ohms•
Power Rating to 50Watt•
Resistance Tolerances to ±0.01%•
TCR to ±1ppm/K•
Load Stability to 0.01%•
For technical questions, contact: powertron@vishaypg.com
USR UNR 4-3425 3825 4020
Powertron
Document Number: 64223
Revision: 20-09-10
www.powertron.de
2
0
20
40
60
80
100
120
25 50 85 100 115 130 145 155
Temperature of the backplate(°C)
Power (% from
nominal power)
Power Rating Notes -
The U-Series Resistors must be attached to a suitable heatsink.
The maximum internal resistor temperature is 155°C.
To specify an appropriate heatsink use the following formula :
RqH = TMAX - ( P x RqR ) - TA
P
Where: RqH = Thermal Resistance of Heatsink ( K/W )
R
qR = Thermal Resistance of Resistor ( K/W )
T
MAX = Maximum Temperature of Resistor
T
A = Ambient Temperature of Heatsink ( °C )
P = Power Through Resistor ( W )
Derating
Temperature Coefcient
SPECIFICATIONS (continued)
Dimensions
USR 4-3425 / UNR 4-3425
Dimension mm
tol.
(±mm) inches
tol.
(±inches)
A 50.00 2.0 1.97 0.079
B 34.00 0.3 1.34 0.012
C 25.00 0.2 0.98 0.008
D 10.00 0.2 0.39 0.008
E 5.00 0.1 0.20 0.004
F 17.80 0.2 0.70 0.008
G Ø3.50 0.1 Ø0.14 0.004
H Ø0.8 0.1 Ø0.031 0.004
I 27.50 0.2 1.08 0.008
J 17.50 0.2 0.69 0.008
K 2.00 0.1 0.08 0.004
L 5.50 0.1 0.22 0.004
M 3.00 0.2 0.12 0.008
-1500
-1000
-500
0
500
1000
1500
DR/R (ppm)
Temperature (°C)
+4,4 ppm/K
-50
-25 025 50 75 100 125
+5ppm/K
-5ppm/K
Nominal Spread
±2.3ppm/K
Nominal DR/R
For technical questions, contact: powertron@vishaypg.com
USR UNR 4-3425 3825 4020
Powertron
Document Number: 64223
Revision: 20-09-10
www.powertron.de
3
Dimension mm
tol.
(±mm) inches
tol.
(±inches)
A 45.40 2.0 1.79 0.079
B 40.00 0.3 1.57 0.012
C 20.00 0.2 0.79 0.008
D 10.00 0.2 0.39 0.008
E 30.00 0.2 1.18 0.008
F 20.00 0.2 0.79 0.008
G Ø3.80 0.1 Ø0.15 0.004
H Ø0.8 0.1 Ø0.031 0.004
I 5.08 0.1 0.20 0.004
J 15.24 0.2 0.60 0.008
K 3.00 0.1 0.12 0.004
L 7.00 0.1 0.28 0.004
M 4.00 0.1 0.16 0.004
USR 4-4020 / UNR 4-4020
USR 4-3825 / UNR 4-3825
SPECIFICATIONS (continued)
USR 4-3825H / UNR 4-3825H
Dimension mm
tol.
(±mm) inches
tol.
(±inches)
A 49.00 2.0 1.93 0.079
B 38.00 0.3 1.50 0.012
C 24.00 0.2 0.94 0.008
D 4.00 0.1 0.16 0.004
E 34.00 0.3 1.34 0.012
F 17.50 0.2 0.69 0.008
G 1.5x45° 0.1 0.6x45° 0.004
H Ø0.8 0.1 Ø0.031 0.004
I 27.50 0.2 1.08 0.008
J 17.50 0.2 0.69 0.008
K Ø3.2 0.1 Ø0.126 0.004
L 2.00 0.1 0.08 0.004
M 5.50 0.1 0.22 0.004
N 15.00 0.2 0.59 0.008
O 3.00 0.2 0.12 0.008
Dimension mm
tol.
(±mm) inches
tol.
(±inches)
A 49.00 2.0 1.93 0.079
B 38.00 0.3 1.50 0.012
C 24.00 0.2 0.94 0.008
D 4.00 0.1 0.16 0.004
E 34.00 0.3 1.34 0.012
F 17.50 0.2 0.69 0.008
G 1.5x45° 0.1 0.6x45° 0.004
H Ø0.8 0.1 Ø0.031 0.004
I 27.50 0.2 1.08 0.008
J 17.50 0.2 0.69 0.008
K Ø3.2 0.1 Ø0.126 0.004
L 2.00 0.1 0.08 0.004
M max.10.3 0.2 max.0.4 0.008
N 15.00 0.2 0.59 0.008
O 3.00 0.2 0.12 0.008
P 19.00 0.2 0.75 0.008
Vishay Precision Group
Document No.: 63999
Revision: 27-Apr-11
www.vishaypg.com
1
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