The level switch is widely used as a level measuring instrument for measuring powder and solid particles. However, if the wiring is incorrect, the level switch will often not work properly or even be damaged. Combined with the wiring diagram, take Huikeda vibrator level switch and Huikeda tuning fork level switch as examples to introduce how to connect the level switch correctly.According to the different output modes, current level switches can be roughly divided into relay output (most commonly used), transistor output (less used), non-contact output (less used), NAMUR output (less used) and two-wire output (The frequency of use is second only to the relay output mode).Since transistor output, non-contact output and NAMUR output are relatively low frequency, this article does not introduce them, but focuses on relay and two-wire connection mode.1 How to correctly connect the switch in the relay output modeThe following figure shows the wiring diagram of the relay output mode of the vibrating rod level switch and tuning fork level switch relay of Huikeda. Huikeda adopts AC/DC intelligent identification in this power supply design, which greatly improves the convenience of power supply wiring.So, how should the position switch in the relay output mode be wired correctly?If a DC power supply is used on site, the DC power supply should be in the range of 20 ~ 72 volts direct current. The positive pole of the power supply is connected to pin 1 of the meter wiring board, and the negative pole is connected to pin 2 of the meter wiring board.If AC power is provided on site, the AC voltage should be in the range of 20 ~ 253 volts AC, so the live wire is connected to pin 1 of the instrument terminal block, and the neutral wire is connected to pin 2 of the terminal block.3-4-5 and 6-7-8 are double-pole double-throw (DPDT) output terminals, the two sets of switches are opened or closed synchronously, 3-4 and 6-7 are normally closed contacts, 4-5 and 7- 8 is a normally open contact. That is, when the power is not on, the relay is released, and the corresponding 3-4 is open and 4-5 is closed; similarly, 6-7 is open and 7-8 is closed.In practical applications, is it normally open (pins 4-5 of the terminal block) or normally closed (pins 3-4 of the terminal block)?Use one or two sets of switches?The answer depends on the actual alarm equipment or the control equipment such as PLC, DCS or sound and light alarm at the application site, but generally speaking, a set of normally closed switches is used in most cases.
Introduce a simple judgment method: first check the low and high toggle switch positions of the material level switch. When a low material level is detected, the switch should be toggled to low; when a high material level is detected, the switch should be turned to high. Location. At this time, if the output wiring is correct, the entire control device should be in normal operation; if the situation is opposite, it is necessary to adjust the normally open or normally closed terminal block contacts. 2 How to correctly connect the blanking position switch in the two-wire output mode The wiring method of the two-wire output mode is as shown in the figure below. Compared with the relay output mode, the connection mode of the two-wire output mode is simpler. However, it should be noted that the two-wire interface of PLC or DCS generally uses 24V power output. The level switch of the two-wire output can only be connected to DC, not to AC. The power supply voltage should be within the range of 10 ~ 36vdc to ensure the normal operation of the instrument . The positive pole of the power supply is connected to pin 1 of the meter terminal block, and the negative pole is connected to pin 2 of the meter terminal block. It can work after power on. The positive and negative poles of the power cord are also signal output lines, which are output in the form of current. 8mA means normal mode (no material at low material level, no material at high material level), 16mA means alarm mode (no material at low material level, and material at high material level). The internal circuit of the PLC or DCS input port (also the power port) can recognize this signal.
Post time: 21-09-21