Data acquisition systems and instruments collect, digitize and process multiple sensor or signal inputs for the purpose of monitoring, analyzing and/or controlling systems and processes.  Data acquisition systems and instruments are configured in a wide variety of instrumentation and modular systems. Applications include manufacturing testing of all types of technical products, safety, environmental, certification and research projects.  Important specifications to consider when searching for data acquisition systems and instruments include differential analog input channels, digital I/O channels, sampling frequency, resolution, accuracy, and datalogger or recorder.  Differential channels use the difference between two signals as an input; common mode is filtered out. In some data acquisition systems and instruments, differential inputs are combinations of two single-ended inputs; in this case, twice the number of differential channels would be available as single-ended inputs.  Digital or discrete channels are used for low-level on-off signals used in applications such as communication, user interface, or control.  Sampling frequency is the frequency of the analog signal sampling and conversion to a digital value.  Resolution refers to the degree of fineness of the digital word representing the analog value. A ten-bit number contains 2¹⁰, or 1024, increments. A 0-10V signal could therefore be resolved into approximately 0.01V increments. A 12-bit representation would be in 2¹² (4096) increments, or divisions of 0.0024V for the same signal. Each additional bit doubles the resolution, and one bit is required for the polarity (sign) of a number.  Accuracy depends on the signal conditioning linearity, hysteresis, temperature considerations, etc. It is represented here as percent full scale of measurement range.  A datalogger or recorder is a unit with instrument functionality with specific capability for data storage. May be for general purpose or application-specific data acquisition.