**esi SR1050 Series 1M & 10 M Resistance Transfer Standard**

- Resistance Values 1 MΩ & 10 MΩ
- Initial Accuracy... ± 25 or 30 ppm of nominal value matched within 10 ppm
- Transfer Accuracy... ± 2 ppm (Typical Short-term Repeatability)
- Calibration Accuracy... ± 10 or 15 ppm

For low resistance transfer standards, consider the esi SR1010 or SR1030

IET Labs continues to manufacturer the SR1050 to the same exacting specs as esi/Tegam

**Introduction**** **Each of the esi SR1050 transfer standards consists of 11 equal steps. These steps are available in increments of 1M Ω, (SR1050-1M) and 10M Ω, (SR1050-10M). The esi SR1050 provides a three terminal connection for each step or for a series of resistance steps. Specially designed lever switches separate each resistor from the others. This allows the standard to be configured in series, parallel, series-parallel, or separately without the use of external shorting bars.

Based on a unique method for establishing known ratios, the esi SR1050 standard utilizes a transfer technique that consists of switching resistance sections in parallel, series or series-parallel sections. An outstanding design feature is a structure in which the only insulation leakage paths (other than those within each resistance section) are from the external terminals to ground. This eliminates insulation leakage errors in the transfer of calibration from one resistance level to another using three-terminal measurement techniques.

A specially designed lever switch provides a convenient means of switching into parallel and series parallel configuration without introducing insulation leakage errors. External shorting or paralleling bars are not necessary. Each resistance section consists of precision wire-wound resistors connected in series. The reduced heat concentration of the series connection improves the thermal characteristics of a resistance element with an already low temperature coefficient

To minimize the cost and difficulty, more practical means of performing such calibrations is to use transfer standards.

If one has a single standard that is calibrated by a national laboratory, one can then compare the transfer standards to the certified standard by ratio techniques. See our Technical Applications section for a full tutorial.

**Specifications**

**Transfer Accuracy **Limited only by short-term repeatability of resistance values. Typical repeatability ±2 ppm

**Initial Accuracy** ±25 ppm of nominal value, matched within 10 ppm, for 1 MΩ, ±30 ppm of nominal value, matched within 10 ppm, for 10 MΩ

**Long-Term Accuracy** ±50 ppm of nominal value

**Calibration Accuracy **±10 ppm for 1 MΩ; 15 ppm for 10 MΩCalibration Conditions 23 ºC, low power, three-terminal measurement

**Temperature Coefficient** ±5 ppm/ºC, matched within 5 ppm/ºC

**Power Coefficient** ±0.05 ppm/mW per resistor

**Maximum Power Rating** 1W/step or 5W distributed over 10 steps, or maximum voltage of 2.5 kV where this value does not result in power excess of 1W per resistor

**Breakdown Voltage **5000 V peak between active terminals and case

**Leakage Resistance** Greater than 10 TΩ from terminals to case

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