Multichannel Pulse Counter for Precise Flow Measurement

Embien as a seasoned leader in the industrial domain, has developed many innovative and requirement centric devices for various customers, especially for industrial automation applications. This case study describes how Embien helped one of our customers in the Beverages industry with a requirement of implementing multi-channel and precise flow control.

Beverage industries use several pipelines running across the plant carrying liquids at different stages of processing. The flow of these liquids needs to be controlled automatically in a precise and fast manner. A team from Embien visited the factory for detailed analysis of the requirements and came up with a solution of a complete setup for flow measurement using digital flow meters, the gateway device and PLC based flow control.

Precise Flow Measurement with digital flow meters

For precise measurement of liquid flow in each pipeline, the pipeline was equipped with a digital flow meter with pulse output. Among various flow meter interface options available, pulse counting provides accurate flow measurements and also cost-effective in terms of signal conditioning circuitry.

There are around 16 pipelines with digital flow meters already installed for the flow management. Each flow meter provided pulse output based on the liquid flow.

There are various options available for reading the pulse output from the digital flow meter. But in this case, we have a large number (16) of pulse outputs from different flow meters. In the existing setup, the PLC is already loaded for most of its functionalities and IOs, it is not possible to monitor the pulses directly. Adding another PLC just to monitor these flows seems more priced.

Renesas RL78/G13 Based Multi-channel pulse counter

Based on further discussions and customer approval, Embien proposed and developed a gateway device with a multi-channel pulse counter option and serial communication for interface with the PLC. Developing the gateway device was challenging which involves the following factors,

      • Selection of MCU with 16 independent channels for pulse input
      • Simultaneous counting of 16 channels of pulse inputs
      • Acquired data manipulation
      • Interface with PLC via serial communication for flow control

Most of the MCU’s available in the market do have more number of channels for pulse inputs, but has less number of counters which is not suitable for simultaneous counting of all the pulse inputs. RL78/G13 series MCU from Renesas provides 16 channels of 16-bit timer array unit with the feature of simultaneous pulse counting. RL78/G13 is powered by RL78 core and is best suited for the industrial applications.

The following figure depict the block diagram of the gateway device,

Multi-channel Pulse Counter

The gateway device is designed with RL78/G13 at its heart. Each channel is optically isolated and standard terminal connectors are provided for easy interface with the digital flow meters. The device includes serial interface for connecting external PLC for flow control.

Firmware is designed such that, the device counts 16 pulse input simultaneously, manipulate the flow from acquired counts and provides the control signals to the PLC via serial interface.

The following figure illustrates the setup at the plant for flow measurement and control,

Multi-channel Pulse Counter

Flow Management System

Flow of the liquid in each pipeline is precisely controlled using the PLC via flow valve and feedback from the flow gateway device. The flow valve is incorporated in each pipeline and the percentage of valve opening or closing can be controlled by simply exciting the valve with a suitable voltage. The percentage of valve opened or closed is fed back to the PLC via 4-20mA analog output. The PLC reads the 4-20mA analog signal and corrects the valve position within a few iterations. The PLC logic is designed suitably with all necessary valve control and analog read mechanisms.

Thus Embien successfully developed and incorporated the multi-channel pulse counter device with the existing setup. The customer is supported by our engineers in installing the device and thoroughly tested the overall setup. Feel free to contact us for your requirements and be part of a success story such as this.

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