What are the steps of relay connection?:
1. Find the coil pin
Use multimeter to measure the resistance between pins. The resistance is between hundreds and 1K ohms. The two pin is the coil pin. Note that some of the relay coil is positive and negative, reverse connection, although not damaged, but not action.
2. Find the normally open and normally closed points
Measuring four pins except outside the coil with a multimeter, two pin conduction is normally closed, plus the 5V DC power to the coil, the relay, they should be disconnected; if not disconnected, within a short relationship.
Add 5V DC to the coil, make the relay move, and then use the multimeter to test. If there are two pins that are not connected, they are normally open.
3, both with the normally open point, but also with the normally closed point related to the pin, that is, the public side.
Note that the flow switch, with the use of relay power and voltage matching, must not be directly connected to the flow switch to the electrical circuit series, so as not to burn out.