Noise Considerations in Resistance Bridges
Joseph M. Diamond
A signal-to-noise analysis is made of the Wheatstone bridge, where the unknown and standard resistors may be at different temperatures, a situation which occurs in resistance thermometry. The limiting condition is assumed to be dissipation in the unknown resistor. It is shown that the ratio arms should be low in resistance compared with the unknown resistor, while the standard resistor should be high. This is true to an extreme degree when the unknown resistor is at liquid helium temperatures, and the standard resistor at room temperature. This factor is much less important in high temperature thermometry, where the noise in the unknown resistor will predominate strongly. An impedance step-up device (transformer or tuned circuit) is valuable in raising the bridge signal and noise level above the noise of the first amplifier tube. However, as the step-up ratio is increased, two counterfactors appear, namely, noise in the loss resistance of the step-up device, and grid current noise. There is therefore an optimum step-up ratio, which has been found. The step-up device is permitted to have a different temperature from the unknown and standard resistors, to evaluate the advantage of cooling it. With certain assumptions about the noise and grid current of the first tube it is found that the equivalent temperature of a unity ratio (Mueller) bridge used for liquid helium measurements may be 400°K.
I E E E Transactions on Instrumentation and Measurement
https://doi.org/10.1109/TIM.1963.4313323
10.1109/TIM.1963.4313323
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resistors Physics & Astronomy 100%
Resistors Engineering & Materials Science 94%
Temperature Engineering & Materials Science 29%
Helium Engineering & Materials Science 27%
liquid helium Physics & Astronomy 25%
temperature measurement Physics & Astronomy 22%
grids Physics & Astronomy 20%
Wheatstone bridges Physics & Astronomy 18%
Diamond, J. M. (1963). Noise Considerations in Resistance Bridges. I E E E Transactions on Instrumentation and Measurement, 12(1), 26-28. https://doi.org/10.1109/TIM.1963.4313323
Diamond, Joseph M. / Noise Considerations in Resistance Bridges. In: I E E E Transactions on Instrumentation and Measurement. 1963 ; Vol. 12, No. 1. pp. 26-28.
@article{dd452e485f6c4a8b9476e731e77c8a2f,
title = "Noise Considerations in Resistance Bridges",
abstract = "A signal-to-noise analysis is made of the Wheatstone bridge, where the unknown and standard resistors may be at different temperatures, a situation which occurs in resistance thermometry. The limiting condition is assumed to be dissipation in the unknown resistor. It is shown that the ratio arms should be low in resistance compared with the unknown resistor, while the standard resistor should be high. This is true to an extreme degree when the unknown resistor is at liquid helium temperatures, and the standard resistor at room temperature. This factor is much less important in high temperature thermometry, where the noise in the unknown resistor will predominate strongly. An impedance step-up device (transformer or tuned circuit) is valuable in raising the bridge signal and noise level above the noise of the first amplifier tube. However, as the step-up ratio is increased, two counterfactors appear, namely, noise in the loss resistance of the step-up device, and grid current noise. There is therefore an optimum step-up ratio, which has been found. The step-up device is permitted to have a different temperature from the unknown and standard resistors, to evaluate the advantage of cooling it. With certain assumptions about the noise and grid current of the first tube it is found that the equivalent temperature of a unity ratio (Mueller) bridge used for liquid helium measurements may be 400°K.",
author = "Diamond, {Joseph M.}",
doi = "10.1109/TIM.1963.4313323",
journal = "I E E E Transactions on Instrumentation and Measurement",
publisher = "Institute of Electrical and Electronics Engineers",
Diamond, JM 1963, 'Noise Considerations in Resistance Bridges', I E E E Transactions on Instrumentation and Measurement, vol. 12, no. 1, pp. 26-28. https://doi.org/10.1109/TIM.1963.4313323
Noise Considerations in Resistance Bridges. / Diamond, Joseph M.
In: I E E E Transactions on Instrumentation and Measurement, Vol. 12, No. 1, 1963, p. 26-28.
T1 - Noise Considerations in Resistance Bridges
AU - Diamond, Joseph M.
N2 - A signal-to-noise analysis is made of the Wheatstone bridge, where the unknown and standard resistors may be at different temperatures, a situation which occurs in resistance thermometry. The limiting condition is assumed to be dissipation in the unknown resistor. It is shown that the ratio arms should be low in resistance compared with the unknown resistor, while the standard resistor should be high. This is true to an extreme degree when the unknown resistor is at liquid helium temperatures, and the standard resistor at room temperature. This factor is much less important in high temperature thermometry, where the noise in the unknown resistor will predominate strongly. An impedance step-up device (transformer or tuned circuit) is valuable in raising the bridge signal and noise level above the noise of the first amplifier tube. However, as the step-up ratio is increased, two counterfactors appear, namely, noise in the loss resistance of the step-up device, and grid current noise. There is therefore an optimum step-up ratio, which has been found. The step-up device is permitted to have a different temperature from the unknown and standard resistors, to evaluate the advantage of cooling it. With certain assumptions about the noise and grid current of the first tube it is found that the equivalent temperature of a unity ratio (Mueller) bridge used for liquid helium measurements may be 400°K.
AB - A signal-to-noise analysis is made of the Wheatstone bridge, where the unknown and standard resistors may be at different temperatures, a situation which occurs in resistance thermometry. The limiting condition is assumed to be dissipation in the unknown resistor. It is shown that the ratio arms should be low in resistance compared with the unknown resistor, while the standard resistor should be high. This is true to an extreme degree when the unknown resistor is at liquid helium temperatures, and the standard resistor at room temperature. This factor is much less important in high temperature thermometry, where the noise in the unknown resistor will predominate strongly. An impedance step-up device (transformer or tuned circuit) is valuable in raising the bridge signal and noise level above the noise of the first amplifier tube. However, as the step-up ratio is increased, two counterfactors appear, namely, noise in the loss resistance of the step-up device, and grid current noise. There is therefore an optimum step-up ratio, which has been found. The step-up device is permitted to have a different temperature from the unknown and standard resistors, to evaluate the advantage of cooling it. With certain assumptions about the noise and grid current of the first tube it is found that the equivalent temperature of a unity ratio (Mueller) bridge used for liquid helium measurements may be 400°K.
U2 - 10.1109/TIM.1963.4313323
DO - 10.1109/TIM.1963.4313323
JO - I E E E Transactions on Instrumentation and Measurement
JF - I E E E Transactions on Instrumentation and Measurement
Diamond JM. Noise Considerations in Resistance Bridges. I E E E Transactions on Instrumentation and Measurement. 1963;12(1):26-28. https://doi.org/10.1109/TIM.1963.4313323