A system designer is rarely able to connect a sensor directly to processing, monitoring, or recording instruments, unless a sensor has a built-in electronic circuit with an appropriate output format. When a sensor generates an electric signal, that signal often is either too weak, or too noisy, or it contains undesirable components. Besides, the sensor output may be not compatible with the input parameters of a data acquisition system, that is, it may have a wrong output format. To mate a sensor and a processing device, they either must share a “common value” or use in-between some kind of a “mating” device. In other words, signals from a sensor usually have to be conditioned and modified before they are fed into a processing device (a load). Such a load usually requires voltage or current as its analog input signal, or a digital code. Nowadays, it is preferable if the sensor’s output is preprocessed and presented at the output in a ready-to-use form. An example is an accelerometer that outputs a digital signal with an encoded number of measured g. Thus, a great majority of sensors that produce analog signals require the interface circuits.