Solid State SCOTT-T Circuit

If there is no isolation requirement for system connection, for rotary transformers larger than zv, the resistor
voltage dividing method can be used to solve the problem. For the self-aligning machine, the so-called solid-state SCOTT
-T circuit can be formed with an operational amplifier according to the method shown in Figure 8-15 . It is recommended to use operational amplifier models such as AD648 (dual operational amplifier ), AD712 (dual operational amplifier), AD713 (quad operational amplifier) . Table 8-9 gives the recommended resistance values ​​for the voltage of self-aligning machines that adapt to various standards . Introducing this circuit can also improve the common-mode rejection ratio (CMRR) of the input to the converter . If the error of the resistor used is controlled within 0.01%, the typical CMRR value is 80dB, and in the worst case, it is 68dB. Since there is a certain deviation in the resistance value, the accuracy of the converter will be lost. If the resistance value deviation is 01%, the angle error caused by this circuit is about 2' (typical value), and the maximum is about 7'. Use the 10-turn variable potentiometer connected to the cos output in Figure 8-15 for fine adjustment to balance the two signals, which can reduce the loss of accuracy.