RMS to DC converter

—us E RFNT MI RROR CAN., , CAV ABSOLUTE VALUE 2 uwaingsnium SINEW 3 10 SQUARER DIVIDFR • iilhammorm sc°^4s One IC and a single capacitor are the only components required for this circuit which will accurately measure the rms value of a given voltage. It enables a DC meter to be provided with AC ranges very simply. Figure 1 shows the circuit which has "nothing to it" as far as construction is concerned. The IC (AD 536) is designed specifically to carry out a complete calculation and determine the rms value of the input signal. On the one hand, the value of capacitor CAV determines the measurement accuracy at lower fre- quencies and on the other, the settling time that the circuit requires to achieve the indicated accuracy. Figure two gives an indication of how the value of CAV is chosen. If, for instance, the value of CAV is 4 pF, it follows that the error at 10 Hz is 0.1% and at 3 Hz it is 1%. The settling time can be read from the right hand vertical axis of figure 2. For 4 ...