Joe M Valdez

US Patent:

50678205, Nov 26, 1991

Filed:

Jun 19, 1990

Appl. No.:

7/540240

Inventors:

Thomas P. Donohoue - Denver CO
Christopher P. Oertel - Arvada CO
William H. Tyree - Boulder CO
Joe L. Valdez - Denver CO

Assignee:

The United States of America as represented by the United States
Department of Energy - Washington DC

International Classification:

G01K 1708

US Classification:

374 31

Abstract:

A circuit for measuring temperature differentials in a calorimeter is disclosed. The temperature differential between the reference element and sample element containing a radioactive material is measured via a wheatstone bridge arrangement of thermistors. The bridge is driven with an alternating current on a pulsed basis to maintain the thermal floor of the calorimeter at a low reference value. A lock-in amplifier connected to the bridge phase locks a signal from the bridge to the input pulsed AC signal to provide a DC voltage. The DC voltage is sampled over time and provided to a digital computer. The digital computer, using curve fitting algorithms, will derive a function for the sample data. From the function, an equilibrium value for the temperature may be calculated.