1、Input power is DC 3-30V, recommended power supply is 12-24VDC. 2、Input power supply, product can generate 4-20mA current output by manual adjusting potentiometer, used for current analog quantity 4-20mA output. 3、Output current can be constant automatically at setting value according to adjustment; it can also be used as a constant current source of which the maximum output current should not exceed 20mA. 4、Universal power supply of module, can be used for PLC, frequency converter, servo. 5、Module power consumption current is less than 30mA, supports for general equipment. Features: Input power is DC 3.3-30V, recommended power supply is 12-24VDC. Input power supply, product can generate 4-20mA current output by manual adjusting potentiometer, used for current analog quantity 4-20mA output. Output current can be constant automatically at setting value according to adjustment; it can also be used as a constant current source of which the maximum output current should not exceed 20mA. Universal power supply of module, can be used for PLC, frequency converter, servo. Module power consumption current is less than 30mA, supports for general equipment. Specifications: Type: Current generator Model: 4-20mA Potentiometer Installation Hold Diameter: 10mm Size(L*W*H): 73*54*30mm/ 2.9* 2.1* 1.2in Hole Spacing: 61mm/ 2.4in    Suitable Screws: M3 (NOT included) Weight: 74g(approx.) Wiring: 3-32V: DC power supply positive GND(left): Power supply negative   GND(right): 4-20mA output current negative 4-20mA-OUT: 4-20mA output current positive Potentiometer: Adjust output range of 4-20mA, clockwise to increase, counterclockwise to reduce Instruction: About Output Impedance Matching: Output signal resistance must meet the following requirements According to the formula:I=U/R(current = voltage/resistance) So the maximum current that signal receiving end can generate is equal to dividing power supply voltage by signal resistance. In this way, current generator still has some resistance. Thus concludes to a formula: Power supply voltage/(signal internal resistance + current generator internal resistance) = output constant current Our module power supply is 5-32V voltage, so if using low voltage power supply, and the signal internal resistance is large, the output constant current will not be enough. Signal matching requirements is given below: For 24V power supply, signal resistance shall not be greater than 1000 ohms. For 12V power supply, signal resistance shall not be greater than 500 ohms. For 5V power supply, signal resistance shall not be greater than 200 ohms. If your signal resistance is greater than the above parameters, you can improve the power supply voltage or reduce internal resistance, to ensure a enough constant current source.Note that the power supply voltage cannot be more than 32V. This module can be used for PLC, frequency converter, servo; and when using these products, the module's voltage should match your interface. If you are not sure, you can try 5V first, then 12V or 24V power supply. Under the condition of normal function,  use low voltage as far as possible.There is another way:In general, PLC, frequency converter, or server has a COM +, COM - power output interface, power supply can be directly from here. Package Includes: 1 x Signal Generator