Type USFS High Voltage, Ultra-Stable,
Low TC Selected Resistor Sets
NewTotal 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

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 areindividually characterized using automated dataacquisition 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 theseselected resistor sets achieves excellent voltage
stability over the operating voltage range.
Multiple USFS Selected Resistor Sets canbe used in series to form a string of resistors
that achieves a higher total resistance and ahigher voltage rating with 2 ppm/°C overalltemperature coefficient. For Custom SelectedResistor Sets contact Applications Engineering.

Model Number

1
Operating
Voltage2
Number ofResistors

3Set
Resistance

4SetTolerance

5Set
TC

6Set
VCSet
Schematic

USFS-3-370-30M-B2

3 kV DC

330 Megohm

0.10%

2 ppm/°C

0.008 ppm/V

Fig. 1A

USFS-5-370-50M-B2

5 kV DC

550 Megohm

0.10%

2 ppm/°C0.005 ppm/V

Fig. 1B

USFS-5-371-100M-B2

5 kV DC

5100 Megohm

0.10%

2 ppm/°C0.005 ppm/V

Fig. 1C

Specifications for the Selected Resistor Sets:

All specifications are valid for the Set Resistance, which isformed by the series connection of the resistors in the selected
Resistor set.

Operating Voltage: The continuous operating voltage forthe set of resistors connected in series. This continuous
voltage may be exceeded by a maximum of 10%.
2 Number of Resistors: The number of resistors in each
Selected Resistor Set, described by the Caddock Part
Number.
3 Set Resistance: The total resistance of the set of resistors
connected in series.
4 Set Tolerance:
The Tolerance of the Set Resistance,measured at low voltage (DC) at +23°C ±2°C.
5 Set TC: The Temperature Coefficient of the Set Resistance,measured at +10°C and +50°C, ref. to +25°C.
6 Set VC: The Voltage Coefficient of the Set Resistance,measured at 10% and 100% of the Operating Voltage.
1Storage Temperature Range: -35°C to +85°C.
High Voltage Design Note: The specifications for these highvoltage resistor sets are based upon the proper high voltage field
stress management, thermal design, and material selection for thehousing which encloses the high voltage resistor set. The designof the housing is the responsibility of the user. These resistors arecompatible with many high voltage potting materials, but issues
regarding potting material adhesion, bubble free potting, andelectrical insulation/isolation are the responsibility of the user.
Dielectric Absorption: The USF resistors are engineered byCaddock 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 canaffect the performance of the circuit. The user is responsible for theselection of materials and the design so that dielectric absorption
and its effects on the performance of the circuit are minimized.

10 Meg

10 Meg= 30 Meg
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 toform the 30 Megohm Resistance.
10 Meg

10 Meg

10 Meg

10 Meg

10 Meg= 50 Meg

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.
20 Meg20 Meg20 Meg20 Meg20 Meg= 100 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 toform the 100 Megohm Resistance.

Figure 2 and Table: Physical Dimensions and Specifications of the individual
USF370 and USF371 Style Resistors that form USFS Selected Resistor Sets
1.500 ±0.020(38.10 ±0.51)
CADDOCK
USFS-5-370-50M-B2
10.0 MEG DATE CODE

0.032 Dia.
(0.81)

0.075 ±0.020(1.91 ±0.51)
0.500 ±0.020(12.70 ±0.51)
0.50 ±0.125(12.70 ±3.18)

1.350 ±0.020(34.29 ±0.51)

Resistor StyleResistanceTolerance

TCUSF370 Style10 Meg±0.20%±10 ppm/°C

USF371 Style

20 Meg±0.20%±10 ppm/°C

ELECTRONICS, INC.

e-mail: caddock@caddock.com • web: www.caddock.com
For Caddock Distributors listed by country see caddock.com/contact/dist.html© 2003-2017 Caddock Electronics, Inc.

10 MegSales and Applications Engineering
17271 North Umpqua Hwy.
Roseburg, Oregon 97470-9422
Phone: (541) 496-0700
Fax: (541) 496-0408
28_IL139.0717