A thermocouple lock-in signal has a noise density referred to its input and a bandwidth

PHYSICS · Subjective · Fermi University Physics · Scientific Practice & Experimental Methods · Electronics, Instrumentation & Communication · Feedback, operational amplifiers and analogue signal processing

Measurement and Method, Ch Designing the measurement: noise, averaging, null and differential methods

Problem

A thermocouple lock-in signal has a noise density en=10 nV/Hze_n = 10\,\mathrm{nV/\sqrt{Hz}} referred to its input and a bandwidth Δf=200 kHz\Delta f = 200\,\mathrm{kHz}. The step between the two states being compared is 0.15 μV0.15\,\mu\mathrm{V}. There is no drift. Averaging each of the two states for the same time tt, find the value of tt needed to reach S/N=15S/N = 15 on the step.

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