Analog flow meter | Siemens S7-1200 PLC flow meter programming example

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What is the issue with the frequency signal output from the e+h flowmeter to the PLC?

The first question involves PLC, which I dont understand. To answer the second question, all flow meters have a standard 4-20mA analog signal. Generally, users transmit this signal to the vertical PLC as instantaneous flow. Some flow meters come standard (or optional) with frequency pulse output, which sends out a high and low level signal. There are two ways to set this signal: 1. As an instantaneous flow output, set it to frequency mode, and use the frequency size to correspond to the instantaneous flow of the corresponding residual search (similar to 4-20mA); 2. As an accumulated output, set it to pulse mode and define a fixed width pulse to represent a fixed flow value (for example, one pulse signal represents 20L). The PLC performs cumulative leakage band addition on this number of pulses to achieve the purpose of measuring accumulated flow. If the PLC uses instantaneous flow to convert accumulated flow, usually a 4-20mA output is sufficient, and this frequency signal is usually used for accumulation. Moreover, the accuracy of the accumulated flow calculated by instantaneous flow conversion is much lower than that calculated by pulse counting.

2. How to control the contactor to close when the flowmeter outputs 4-20mA, that is, to make contact when the flowmeter outputs 4mA When using analog signals for contactor control, there is indeed a certain degree of complexity in the process of pulse training. For example, when the flow meter output is 4mA, the contactor is disconnected, and when it is 20mA, the contactor is closed. However, in the intermediate state between 4 and 20mA, the control logic of the contactor needs to clarify the cancellation. How to adjust the status of the contactor if the flow rate varies between 4mA and 20mA? Specifically, if the analog output is between 4 and 20mA when the flow rate increases, will the contactor remain disconnected? On the contrary, when the flow rate decreases and the analog output is between 4 and 20mA, does the contactor remain in a closed state? Until the flow rate drops to 4mA, the contactor will disconnect again. This control logic may lead to frequent switching of the contactor in practical applications, which not only increases the workload of the contactor, but also may affect its service life and stability. Therefore, using switch signals for control may be more reasonable. The switch signal can directly control the on/off of the contactor without considering changes in the intermediate value, simplifying the control logic and improving the stability and reliability of the system. If you have specific control requirements, such as when the contactor should open or close, please provide a detailed description to provide a more accurate solution.

3. Example of Siemens S7-1200 PLC flowmeter programming

The core of Siemens S7-1200 PLC flowmeter programming is to read the standard signal of the flow sensor through the analog input module, and perform engineering value conversion and accumulation calculation.

1. Hardware Configuration and Wiring 1 The hardware configuration ensures that the PLC system includes: - one S7-1200 CPU (such as CPU 1214C) - one analog input module (such as SM 1231 AI 4x12 bit) - one flow meter (outputting 4-20mA or 0-10V standard signals) 2 Module configuration in TIA Portal software: - In the device configuration of the project v

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