SR102/103/104 Series

  • Highest accuracy (1 ppm/yr) and stability (±0.5 ppm/yr typical) of any resistance standard
  • Lowest temperature coefficients (< 0.1 ppm/ºC)
  • Available in 3 models: 100Ω, 1000 Ω, 10,000Ω.
  • Has remained the foremost resistance standard, with no equivalent, for over 35 years
  • 5 Year Warranty Included
  • The primary standard of National Metrology Labs throughout the world
  • Has remained the foremost resistance standard, with no equivalent, for over 35 years
  • Oil filled, hermetically sealed; units can be supplied without cases for use in oil bath
  • ISO/IEC-17025 Accredited Calibration Included
  • Alpha Beta Measurements Included
Prices range from $7,395.00 to $8,470.00
Prices range from $7,395.00 to $8,470.00
Estimated Delivery is 15 to 50 weeks

The World's Most Stable Resistance Standard

IET continues to manufacturer the SR102 & SR104 to the same exacting specifications as esi/Tegam

The esi SR102, SR103 & SR104 are a highly stable (±0.5 ppm/year) and accurate (1 ppm), 100 Ω, 1 kΩ, 10kΩ resistance standards. The SR102, SR103 and SR104 Standards are equipped for five-terminal measurements used for Standard Resistor readings and for Temperature Sensor readings. Individual calibration data, which identifies the standard deviation, and the temperature coefficients, is supplied with each unit. In addition, each unit is equipped with a thermal well so that the exact temperature of the resistance standard is known. This allows the user to make highly precise, temperature compensated, measurements.

esi SR102 100 Ω Primary Resistance Standard
These resistance standards were designed to provide an important link between Quantum Hall resistance values and traditional decade resistance values. 100 Ω provides unique reference capability.

esi SR103 1000 Ω Primary Resistance Standard
New resistance standard recently developed to improve the range of primary standards available.

esi SR104 10 KΩ Primary Resistance Standard
This has been the long-standing industry standard for the 10 kΩ. This everlasting standard is the benchmark for high accuracy, stability and low temperature coefficients for calibrations requiring traceability to the SI.

The SR102, SR103, and SR104 Precision Transportable Resistance Standards are oil filled, hermetically sealed, five-terminal resistance standards designed for precision bench top or oil bath applications.

The long-term stability of these resistance standards is typically less than 0.2 ppm per year and temperature coefficients are less than 0.1 ppm per degree Celsius.

esi Primary Standard History

esi originally designed the SR104 in the late 1960s or early 1970s. The primary resistance standards consists of at least 10 equal resistors (R) that are connected in series, parallel, or series-parallel. This results in resistance values that are l0R (SR104), R/10 (SR102), or R (SR103).

Excellent long-term stability and low temperature coefficient was achieved by using matched groups of resistors, constructed using the alloy Evanohm-R on a mica card.

The New IET Labs SR104 Design
In January of 2007 IET Labs purchased the esi resistance product line from Tegam. TEGAM had acquired the esi (Electro-Scientific Industries) product line in 1993 from esi.

The new SR102, SR103 and SR104 are no longer designed using Evanohm-R wire but instead use 10 custom hermetically sealed oil-filled Bulk Metal® Foil resistors.

Each resistor is individually tested and then combined in sets that are matched for absolute tolerance and temperature coefficient.

These sets are then allowed to age typically for several years before use.

The resistors are still connected in series, parallel, or series-parallel to achieve the final resistance value.

Each SR102, SR103 and SR104 is tested using an MI6010 and transfer standards that are calibrated annually by primary standards labs such as NRC. Typical calibration uncertainty is < 0.4 ppm.

The resulting low temperature coefficient allows high performance applications of these standards inside or outside an accurately controlled temperature environment.

Maximum accuracy is calculated as a temperature corrected resistance value. This is accomplished by using the built-in RTD temperature sensor to measure the internal temperature and referencing a temperature correction chart provided with each unit. The measurement accuracy of the built-in RTD thermometer is better than 0.1 degree Celsius.

Very low power coefficients are achieved by using standard resistors constructed with large surface areas like our original Model SR104, 10 kΩ standard resistor. The resistors are surrounded by oil to conduct heat generated by the measuring currents out through the stainless steel case.

These characteristics facilitate precise laboratory comparisons without critical environmental controls and are used wherever a need for a very accurate, stable resistor of low temperature coefficient is required.

100 ohm Transportable Resistance Standard: SR-102
1,000 ohm Transportable Resistance Standard: SR-103
10,000 ohm Transportable Resistance Standard: SR-104
For deleted case version add -DC at the end of the part number

Each unit includes:
5 Year Warranty
Built-in temperature sensor
Temperature correction chart
Instruction manual
ISO/IEC 17025 calibration certificate


Stability First 2 years: ±1 ppm/year, thereafter: ±0.5 ppm/year
Temperature coefficient
Alpha: <0.1 ppm/°C at 23°C
Beta (1/2 rate of TC change):<0.03 ppm/°C from 18°C to 28°C
No ovens or external power required
Power coefficient<1 ppm/W
Adjustment to nominal ±1 ppm
Measurement uncertainty <0.32 ppm
Max voltage 500 V peak to case
Power rating 1 W (Momentary 100 W overloads will not cause failure)
Thermal emf Thermal emf at the terminals does not exceed ±0.1 μV under normal conditions.
Insulation resistance All terminals maintain a minimum 1012 Ω to ground
Internal temperature sensor 100 Ω, 1 k Ω, or 10 kΩ resistor with 1,000 ppm/°C temperature coefficient. Integral thermometer well is provided for calibration
Hermetic sealing To eliminate the effects of humidity, the resistor is hermetically sealed in oil with metal-to-glass seals. The resistance changes
<±0.1 ppm with normal atmospheric pressure and humidity changes.