By temperature controlling an otherwise very stable resistor, a performance close to the very best available in the
world can be achieved at a surprisingly low price. The resistor itself is oil filled and hermetically sealed.
The function of hermetic sealing is to eliminate the ingress of moisture and oxygen both of which play a role in
the long term degradation of unsealed resistors. A further enhancement in both short and long term stability is
achieved by oil filling. The oil also acts as a thermal conductor allowing the device to accept short periods of
overload without degradation.
With accuracies of ±0.005% and a resistance range from 5Ω to 3.3 MΩ and long term drift of less
than 5ppm, these devices are virtually secondary standards that can be kept in a laboratory as references to
calibrate other devices.
The Resistor is held in a temperature controlled environment heated to 30±0.1°C other temperatures are
available to special order. The heater requires 2 watts at 5V which can be supplied by a battery or an unregulated
DC supply. In an ambient of 20°C the Resistor's heater will warm up in typically 30 minutes, and a LED shows
when the temperature has been reached. A test pocket is provided so that the resistors' temperature can be
monitored if required.
0.1 ppm/month or better stability can be expected.
We can supply the value you choose ±0.1% between a minimum of 5Ω and a maximum of 3.3 megaΩ.
However we bulk buy and keep in stock the following standard values: 10W, 25W, 100W, 1000W, 10,000W.
For the highest quality traceability we recommend that the 456 be UKAS Certified. We can offer the 2 Sigma Uncertainties shown in the table.
456 Product Spec Sheet
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