Overview/

With the improvement of automation level, many traditional production process enterprises are striving to achieve automation and digital control. Quantitative injection (control) is widely used in industries such as food and beverage. This article introduces a simple quantitative control method using the alarm output function of electromagnetic flow meters.

　　/Application Introduction/

There are IN+and AL on the terminal block of the electromagnetic flowmeter. By connecting the lead wires of these two terminals to the "start button" or "start control signal" (see the figure below), quantitative control can be achieved to start synchronously.

Figure 1 External synchronous start switch

When the start button is pressed, the converter records the "current cumulative amount" and calculates the "target cumulative amount" based on the quantitative value, starting counting.

When the target value is reached, output a level control signal (output by terminals AH and COM), and the target value can be freely set according to the actual control needs.

　　/Control method/

　　

The following are actual circuit diagrams of two control methods for on-site application reference.

　　

　　1. Level control method

If the external quantitative control circuit adopts the method shown in Figure 2, AH will be at a high level to COM before the quantitative control is reached; If the quantitative value is reached, AH will jump to a low level for COM.

Figure 2 Level Control Method

　　2. Relay control mode

If the external quantitative control circuit adopts the method shown in Figure 3, the normally open node of the relay can be used. When the quantity is not yet reached, the internal transistor is turned off, the coil is not powered, and the node is disconnected; If the quantitative value is reached, the internal transistor conducts, the coil is energized, and the node is closed.

Figure 3 Relay control mode

The implementation of the above functions must ensure that the measurement direction of the electromagnetic flowmeter is forward measurement and has cumulative function.

　　/Menu settings/

　　

The hardware function has been implemented, and the next step is to set two menu functions closely related to quantitative control on the flowmeter: "Flow Accumulation Unit" and "Quantitative Control Settings".

　　1. Flow accumulation unit

According to the needs, the flow accumulation units can be selected as 0.001m ³, 0.01m ³, 0.1m ³, 1.0m ³, 0.001L, 0.01L, 0.1L, and 1.0L.

　　2. Quantitative control setting

This menu is used to set quantitative values. For example: 2.000m ³.

After completing these settings, a complete and reliable quantitative control system can be put into use, which can greatly reduce the labor intensity of workers and greatly improve the reliability and accuracy of production process control.

　　/Header display/

　　

Finally, during the quantitative control process, the display content on the meter head can be switched by pressing the "down" button, and the LCD can go down to display:

+00000 43.000m ³ (positive cumulative amount)

DL 2.000m ³ (quantitative value)

+00000 45.000m ³ (target cumulative quantity)

The above example shows that if the current cumulative amount is 43.000m ³ and the quantitative value is 2.000m ³, then the target value of the quantitative trigger signal is 45.000m ³.