Specifications
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Earth
6BA Brass
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Weight
680g
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Element
Strain free, immersed in dry oil (no. 4 Kerosene)
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Stability
2ppm/year (0.5ppm/ year to special order)
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Top Panel
Bakelite with PFTE inserts and engraved lettering
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Dimensions
Container 114 x 74mm dia. Overall 140 x 83mm dia.
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How to order
Standard resistor. Please specify type, resistance value and calibration option.
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Construction:
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Type SRA Values
1, 10, 25, 100 Ohms, 400 Ohms to special order
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Type SRB Values
1000 10,000 Ohms
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Maximum Dissipation
1 Watt
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Terminal – current
0BA Copper
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Accuracy of Adjustment
±20ppm
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Calibrated Uncertainty
0.3ppm (see UKAS schedule)
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Terminal – Potential
4BA Copper
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Recommended Dissipation
10 mW
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Approximate load coefficient
6ppm/ Watt
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A.C./D.C. transfer error at 1kHz
1ppm 10Ω – 10kΩ. 5ppm – 1Ω
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Temperature coefficient of resistance
2ppm / °C 0.5ppm made to special order
Eventually all resistance thermometry refers back to one or more fixed resistors. These are a key element in any laboratory which measures temperature. The resistors need to be very stable with time, temperature and transportation, and they need to have negligible inductance and capacitance.
They also need to have a long and successful history of use. Wilkins and Swan at our National Physical Laboratory (NPL) developed a resistor design flexible enough to allow windings with various resistance values to be made available and stable enough to be accepted world-wide as resistance standards. Particularly important is that the AC/DC characteristics are the same up to about 1000 Hz.
This design has been licensed to H. Tinsley & Co. who have been producing (and have made further improvements to) this product since 1970. Isotech are pleased to be able to offer this design of resistor made for us by Tinsley with 1 of 2 calibration possibilities:
UKAS with an uncertainty of ±0.3ppm (SRA models). NPL with an uncertainty of ±0.1 ppm (dependent on resistance value).
