$\pm 30 \mu K$ temperature controller from 25 to $103^o$ C: Study and analysis

Unni, Madhavan PK and Gunasekaran, MK and Kumar, A (2002) $\pm 30 \mu K$ temperature controller from 25 to $103^o$ C: Study and analysis. In: Review of Scientific Instruments, 74 (1). pp. 231-242.

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Abstract

A simple two-stage metal thermostat, having a wide tolerance, has been built for performing light scattering studies in multicomponent liquid systems. It gives a temperature stability of $\pm$ 30–45 $\mu$K for 1$\frac{1}{2}$ 4 h and $\pm$ 60–90 $\mu$K for 7–14 h over a broad range of 25–$103^o$ C. A detailed profile of thermal gradients within the sample recess is provided. The parameter ${\triangle}T{_e_f_f}$ [i.e., the difference between the maximum (minimum if ${\triangle}T_{eff}$ has a negative value) temperature within the sample recess and the temperature just outside the sample recess] seems to be more relevant than $\triangle$T (i.e., the temperature difference between the inner and the outer stages) in understanding the behavior of our thermostat. The thermal gradients can be tuned by varying ${\triangle}T_{eff}$ (or by varying $\triangle$T). The least values of horizontal and vertical thermal gradients, i.e., 250 and 100 $\mu$ K/mm, respectively, are observed for ${\triangle}T{_e_f_f}$ = 4.46 mK. The transient response of the controller is almost invariant for ${\triangle}T{_e_f_f}>0$, but it shows a dramatic decrease of almost 50% when ${\triangle}T_{eff}<0$. On the whole, the limit ${\triangle}T_{eff}\rightarrow{0}$, provides the best operating condition from all standpoints. A simple and effective compensation scheme to null the effect of extraneous parameters is employed. The importance of the stability of the bridge excitation source in improving the long-term stability of the controller is established.

Item Type: Journal Article Copyright of this article belongs to American Institute of Physics. Division of Physical & Mathematical Sciences > Physics 27 Dec 2007 19 Sep 2010 04:28 http://eprints.iisc.ernet.in/id/eprint/7228