Analog input ranges or levels are specified for each 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.

An analog inputs can be either unipolar (e.g., 0-5 V) or bipolar (e.g., ±10 V). Inputs may also be either single ended (measuring the voltage difference between the input and 0 V) or differential (measuring the difference in voltage between two different inputs). An analog input with an amplifier configured differentially will have a common mode voltage range which allows the input to measure voltages from sources that do no share the same ground as the input system. 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 analog input is typically implemented in the form of an instrumentation amplifier. An instrumentation amplifier has a differential input configuration, but also usually offers software programmable gain capabilities that allow the maximum flexibility in selecting the appropriate gain setting for the application.

For many sensor-based measurement applications, it is necessary to use a high-performance signal conditioning module as the front end to the 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.

Measurement Computing Corporation offers the largest selection of PC-based data acquisition and measurement products. Shop our online catalog by selecting a category above. From PCI, USB, PC/104, ISA, and PCMCIA bus to RS-232, RS-422, RS-485, and GPIB interfaces; Measurement Computing has everything you need for your PC-based data acquisition and control applications.