Quote:
Originally Posted by Craig Sawyers
32C (305K) - 34 ohm/m
77K (LN2) - 33.4 ohm/m
4.2K (LHe) - 33.2 ohm/m
Since the resistance of NiCr stays pretty much constant all the way down to 4.2K you get absolutely no noise benefit from cooling the resistors.
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But at room temperature, over a 20kHz bandwidth, a 1kΩ resistor generates 0.57μV rms Johnson noise. At LN2 temperatures it generates 0.29μV and at LHe temperatures it generates 68nV rms. Nine times less! And owing to the low tempco, it's still a 1kΩ resistor...