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Note the bit resolution of the ADC we'll call this n.A pressure sensor with a 20 mV full-scale output at a full-scale pressure of 10,000 psi assigns a value of 10,000 to variable E. Determine what V S represents in terms of engineering units we'll call this E.I'll deal with that in a special example later. Note that some transducers have a 4-20 mA process current output. it has a maximum output signal magnitude in volts (or millivolts) that you assign to variable V S. Even if your signal source is a transducer that measures torque, pressure, load, etc. Determine the full-scale output voltage range of the signal you want to measure we'll call this V S.Determine your range in volts and assign it to variable V D.
Some data loggers offer fixed ranges, and others allow variable ranges.
Determine the full-scale input voltage range of the data logger (from the amplifier's input, if one is used) we'll call this V D. You have to start with basic information: Likewise, high ADC resolution is sometimes handy and sometimes overkill, but it's more difficult to quantify where the breakpoints are. But it may come in handy for sizing up the miter joints of the dining room cabinet you're building. Depending upon what you're trying to do the higher resolution may be overkill, like measuring the length of your driveway. Using an example we're all familiar with, a ruler calibrated in 1/16th of an inch offers sixteen times the resolution of another calibrated only in whole inches. That refers to how finely it slices its full-scale measurement range, or in other words, the smallest change in the input signal that it can theoretically measure (ignoring noise). The bit value of an analog-to-digital converter refers directly to its resolution. You just bought a data logger or data acquisition system with a 14-bit ADC (analog-to-digital converter.) What exactly does that mean? Could you have gotten away with a 12-bit product? A 10-bit? Did you gaffe and really need a 16-bit data logger? You know that a higher "bit" number is better, but how much better is "better"? This application note describes a method you can use to answer these questions in terms of your specific situation, as opposed to the generalized explanations provided by product data sheets.įirst, some background. How Much ADC Resolution Do You Really Need?
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