Accuracy of RMS-to-DC is also a very important specification, often the most important. For RMS-to-DC converters, many kinds of errors have to be considered: total error with or without external trimming, error with power supplies, and DC reversal error. The error specifications have to be read carefully and their maximum values will be critical for the system design. Normally, the maximum values of these errors are provided. Error specifications for the AD637B, the highest accuracy RMS-to-DC converter, are shown here as an example. Crest factor is the ability of an RMS-to-DC converter to accurately convert short duty cycle waveforms or those with high peaks and relatively small energy. Therefore the error due to the signals' crest factor will be critical in a great many applications. The accuracy varying with frequency is related to the value of the averaging capacitor, and this is a trade-off between accuracy and settling time. Plots are provided in the datasheet to assist with capacitor value selection. Linearity is important in wide dynamic range systems. This specification is different from the input range. Again, minimum percentages of linearity error denote higher accuracy across the input range. The maximum nonlinearity error of an AD637B for a 1 volt input signal is 0.02% of the 2 volts full scale, which is 0.2mV RMS.