First there is a cost difference between the 3 ½ digit and 4 ½ digit displays, that can sometimes be substantial. The 4 ½ digit display provides a level of resolution for small scale inputs that may not provide much value to the viewer. The resolution can be 1/100 of an Amp for example, thus for a 50 AC Amp measurement, a value such as 50.01 AC Amp would be presented. If however a 3 ½ digit display had been used for the same measurement a resolution of 1/10 of an Amp would result in a measurement of 50.1 AC Amp. The end user may find the result is more stable and easier to read and potential record if necessary. If however a value of more than 199.1 is required, with a 1/10 resolution a 4 ½ digit display is needed. Always remember that a panel meter is displaying results only for human consumption.
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