CHAPTER 1 B IOMEDICAL S ENSORS T EMPERATURE S ENSOR T ECHNOLOGY P. A. Kyriacou School of Engineering and Mathematical Sciences City University, London, UK The clinical thermometer ranks in importance with the stethoscope. A doctor without his ther- mometer is like a sailor without his compass. --Family Physician, 1882 1.1. INTRODUCTION Human body temperature is of vital importance to the well-being of the person and therefore it is routinely monitored to indicate the state of the person's health. Despite the fact that temperature Celsius thermometer (attached to a barometer) made by J. G. Hasselström, Stockholm, late eighteenth century. 1