First, DAQ is an abbreviation for data acquisition. DAQ analog input refers to the analog inputs provided by a data acquisition board or card. For the most part, a typical A/D data acquisition board or card has an input range of 0-5 V, 0-10 V, +/-5 V or +/-10 V. However, some analog input ranges can be as low as 0-100 mV or +/-100 mV. It is always best to check the specification to see if the board or card that you are interested in has a fixed analog input range or is user programmable and what ranges are available.

A DAQ analog input range that is unipolar (e.g., 0-5 V) has an input amplifier that is configured in a basic unit gain configuration. Bipolar inputs measure both positive and negative voltages (e.g., ±10 V). Typical DAQ board inputs can be either single ended or differential. A DAQ analog input with an amplifier configured differentially will typically have a common mode voltage range of ±10 V. This is very helpful when making measurements where the signal being measured might be offset from ground.

For other applications like that of measuring sensor signal data, the DAQ analog input should be in the form of an instrumentation amplifier. An instrumentation amplifier has a differential input configuration, but also offers software programmable gain capabilities that allow the maximum flexibility in selecting the appropriate gain setting for the application.

For most sensor-based measurement applications, it is best to use a high-performance signal conditioning module as the front end to the DAQ analog input of your A/D data acquisition board or card. Sensors like thermocouples and strain gauges require added conditioning such as precision excitation, cold-junction compensation, low noise amplification, etc.

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