Sometimes it is not absolute temperature value that is of interest, but rather any small changes in that value. The circuit described here does not just measure these changes: it reports them both visibly and audibly. Using just a few active components it achieves a temperature resolution of just one tenthousandth of a degree.Measuring temperature is a fairly simple task, but doing so precisely takes rather more skill, particularly when it is desired to obtain readings to a resolution of better than one tenth of a degree. The circuit presented here measures temperature to a resolution of one ten-thousandth of a degree, using just four active components and an optional display. The purpose of the circuit is to be able to detect even the smallest change in temperature: the emphasis is much more on extreme sensitivity and resolution than on absolute accuracy.