The subject of this book is the recovery of signals from noise in electronic instrumentation. The term "electronic instrumentation" is sometimes reserved for instruments such as the oscilloscope and testmeter which are used to measure specifically electrical variables. It should therefore be made clear that the scope of the book goes much beyond this and covers instrumentation for the measurement of any variable, whether electrical or not. The term "electronic" simply implies that electronic techniques are used in the process of measurement. The term "noise" also requires clarification. Until recently, it was used mainly to refer to random fluctuations such as white and 1/F noise. Now, the term is used to refer to almost any kind of unwanted signal in an electronic system. It is in the broader sense that the term is used in the title, since the recovery of the required signal from many kinds of unwanted signal is covered. These comprise offset, drift, random noise comprising white and 1/F noise, and interference. The text is intended for anyone who is involved in the development of electronic instrumentation.