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Corporate Office

1717 Chicago Avenue

Riverside, California 92507-2364

Phone: (951) 788-1700

Fax: (951) 369-1151

Applications Engineering and Sales

17271 North Umpqua Hwy.

Roseburg, Oregon 97470-9422

Phone: (541) 496-0700

Fax: (541) 496-0408

L-423.1012

e-mail: caddock@caddock.com • web: www.caddock.com

For Caddock Distributors listed by country see caddock.com/contact/dist.html

Type USFS - Ultra-Stable Selected Resistor Sets

are designed for use in High Voltage Systems

that require the very best temperature stability

and long term stability. These Selected Resistor

Sets are manufactured with Caddock’s Tetrinox®

Resistance Film System.
The individual USF Style resistors that form

these Ultra-Stable Selected Resistor Sets are

individually characterized using automated data

acquisition systems and then selected to form

a Set Resistance with an Absolute Temperature

Coefficient (TC) of 2 ppm/°C maximum.
The low Voltage Coefficient (VC) of the USF370

and USF371 Style resistors used in these selected

resistor sets achieves excellent voltage stability

over the operating voltage range.
Multiple USFS Selected Resistor Sets can be

used in series to form a string of resistors that

achieves a higher total resistance and a higher

voltage rating with 2 ppm/°C overall temperature

coefficient. For Custom Selected Resistor Sets

contact Applications Engineering.

Type USFS High Voltage, Ultra-Stable,

Total Set Resistance up to 100 Megohm with

Absolute TC of 2 ppm/°C

Voltage Ratings up to 5000 Volts DC - Custom Selected Resistor Sets Available

Low TC Selected Resistor Sets

Model Number

Set

Schematic

USFS-3-370-30M-B2
USFS-5-370-50M-B2
USFS-5-371-100M-B2

3 kV DC
5 kV DC
5 kV DC

3
5
5

30 Megohm
50 Megohm
100 Megohm

2 ppm/°C
2 ppm/°C
2 ppm/°C

0.008 ppm/V
0.005 ppm/V
0.005 ppm/V

Fig. 1A
Fig. 1B
Fig. 1C

0.10%
0.10%
0.10%

Operating

Voltage

Number of

Resistors

Set

Resistance

Set

Tolerance

Set

Storage Temperature Range: -35°C to +85°C.
High Voltage Design Note: The specifications for these high

voltage resistor sets are based upon the proper high voltage field

stress management, thermal design, and material selection for the

housing which encloses the high voltage resistor set. The design

of the housing is the responsibility of the user. These resistors are

compatible with many high voltage potting materials, but issues

regarding potting material adhesion, bubble free potting, and

electrical insulation/isolation are the responsibility of the user.
Dielectric Absorption:

The USF resistors are engineered by

Caddock to minimize dielectric absorption. The circuit board, potting,

or encapsulation materials that are in contact with, or in circuit with

the USF resistors, can exhibit dielectric absorption behavior that can

affect the performance of the circuit. The user is responsible for the

selection of materials and the design so that dielectric absorption and

its effects on the performance of the circuit are minimized.

Figure 2 and Table:

Physical Dimensions and Specifications of the individual

USF370 and USF371 Style Resistors that form USFS Selected Resistor Sets

0.500 ±0.020

(12.70 ±0.51)

0.50 ±0.125

(12.70 ±3.18)

1.350 ±0.020

(34.29 ±0.51)

0.032 Dia.

(0.81)

0.075 ±0.020

(1.91 ±0.51)

CADDOCK

USFS-5-370-50M-B2

10.0 MEG DATE CODE

1.500 ±0.020

(38.10 ±0.51)

Resistor Style

Resistance

Tolerance

USF370 Style

10 Meg

±0.20%

±10 ppm/°C

USF371 Style

20 Meg

±0.20%

±10 ppm/°C

Figure 1A:

Schematic of the three 10 Megohm USF370 Style resistors in a

USFS-3-370-30M-B2 Selected Resistor Set, which are connected in series to

form the 30 Megohm Resistance.

Figure 1B:

Schematic of the five 10 Megohm USF370 Style resistors in a

USFS-5-370-50M-B2 Selected Resistor Set, which are connected in series to form

the 50 Megohm Resistance.

10 Meg

= 30 Meg

= 50 Meg

10 Meg

Figure 1C:

Schematic of the five 20 Megohm USF371 Style resistors in a

USFS-5-371-100M-B2 Selected Resistor Set, which are connected in series to

form the 100 Megohm Resistance.

= 100 Meg

20 Meg

Specifications for the Selected Resistor Sets

All specifications are valid for the Set Resistance, which is formed

by the series connection of the resistors in the selected Resistor

set.

Operating Voltage:

The continuous operating voltage for the

set of resistors connected in series. This continuous voltage

may be exceeded by a maximum of 10%.
Number of Resistors:

The number of resistors in each

Selected Resistor Set, described by the Caddock Part Number.

Set Resistance:

The total resistance of the set of resistors

connected in series.

Set Tolerance:

The Tolerance of the Set Resistance, measured

at low voltage (DC) at +23°C ±2°C.
Set TC: The Temperature Coefficient of the Set Resistance,

measured at +10°C and +50°C, ref. to +25°C.
Set VC: The Voltage Coefficient of the Set Resistance,

measured at 10% and 100% of the Operating Voltage.

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