**Components of the AC and DC units**

#### a. Frequency converter/regulator

Frequency converters, also known as frequency inverters, are electronic devices that convert alternating voltage into direct current and then back into alternating current at variable voltage and frequency. In our setup, we used this device to convert the current from the grid frequency of 60 Hz into the frequency applied to the electrode, of 1 to 120 Hz.

#### b. Potentiometer

A potentiometer is an electronic component that has adjustable resistance, providing variable the output voltage to the electrode.

#### c. Step-down transformer

A step-down transformer is used to lower single-phase, two-phase or three-phase voltage, to adapt the grid voltage to the needs the equipment to be used. Its primary winding is electrically isolated from the secondary winding. A mesh (electrostatic shield) can be placed between the windings, which once grounded helps eliminate noise from the power grid. In the case of electrolytic treatment here, the input voltage of 110/220 V was transformed to output voltage according to the operational need, e.g., 15 V.

#### d. Voltmeter

This is a device that measures voltage in a circuit. The voltage is generally shown by a movable pointer or a digital display. They are designed so that the high internal resistance introduces minimal changes to the circuit being monitored. To measure the voltage difference between two points in a circuit, the voltmeter is placed in parallel with the section of the circuit between these two points. Therefore, to obtain precise measurements, the meter should have a very large resistance compared to the circuit. Voltmeters can measure DC and AC voltages, depending on the quality of the device.

e. Ammeter

An ammeter is an instrument used to measure the intensity of electrical current flow passing through the cross section of a conductor. Since the current flows through the conductor and the devices attached to it, to measure the current passing through a region of a circuit, the meter must be placed in series with the circuit section. Therefore, to obtain precise measurements, the ammeter should have a resistance that is very small compared to the circuit. Ammeters can measure continuous or alternating current.

#### f. Bridge rectifier

This is a device that converts alternating current (AC) (usually sinusoidal) into direct current.

#### g. Polarity reversal switch

This is an important element of treatment systems, by increasing the lifetime of the electrode and reducing the resistance of the system. It changes the anode to the cathode and back again at regular intervals, to reduce erosion and scaling.
