Systems and methods are described that facilitate assisting a user in filling forms. During playback mode, the recorded data is used to exercise the system as probes collect actual data for comparison to expected data. When the user touches the constant current electrode pair and the voltage measuring electrode pair, the fat measuring control circuit firstly applies a predetermined current to the constant current electrode pair. While the boosting operation is being suspended, the second switch operates to lower the output voltage. A spacer piece is mounted on at least one first or second expanding arm, such that the height of the spacer piece determines the minimum separation, to which the first and second expanding arms can be pressed together.