Rheometer Control System Based on Single-Board RIO


"The powerful FPGA and compact form factor of the Single-Board RIO device allows us to create a rheometer control system that satisfies all customer requirements."

- Rafayel Ghasabyan, RAFA Solutions LLC

The Challenge:
Developing a rheometer control system to continuously monitor flow properties of liquids in the pipe in real time to maintain products within specifications during manufacturing and processing.

The Solution:
Combining the benefits of Single-Board RIO hardware and LabVIEW software to create a rheometer control system capable of working continuously for long periods.

Rafayel Ghasabyan - Find this author in the NI Developer Community

About RAFA Solutions

RAFA Solutions, established in 2012, is a systems integrator company specializing in smart machines and data acquisition and control systems. The company, an NI Silver Alliance Partner, develops and manufactures daughterboards for Single-Board RIO, FlexRIO, and CompactRIO products. RAFA Solutions also provides market-ready products and services for the development of custom modules and solutions. Our team offers expertise in embedded design and development in many industries including material science, oil and gas, food, and mining.

Problem Background and Solution

A rheometer control system continuously monitors the flow properties of liquids in the pipe in real time. The operations principle of the system is based on squeeze-flow technique. It measures storage and loss moduli by imposing a small cyclic deformation on a liquid sample at a variety of frequencies. It measures the response of the liquid to calculate the viscosity.

The system we developed provides instant and accurate rheological data (viscosity) in real time to maintain products within specification during manufacturing and processing. The system requires the control of an actuator using a proportional-integral-derivative (PID) closed-loop control system and data acquisition from different sensors.

Figure 1. Rheometer System Installed on the Pipe

We developed a hardware platform for the rheometer control system that provides signal conditioning for strain gage, load cell, and RTD sensors, and control of actuators. The system consists of two boards (high voltage and low voltage), which work in conjunction with an sbRIO-9606 device.

We chose Single-Board RIO as the system’s hardware platform. The system needed a powerful FPGA and processor to implement accurate data acquisition, waveform generation, and PID control. We built the system using the sbRIO-9606 device featuring a 400 MHz processor, 256 MB DRAM, a Xilinx Spartan-6 FPGA, and 96 digital I/O lines.

A low-voltage board implements functions of signal conditioning and data acquisition from different sensors to deliver data on system parameters, control and monitoring of digital I/O, and signal generation for control of a piezo actuator. We intend to use a high-voltage board to amplify a piezo actuator control signal and form the amplifier’s power supply.

Figure 2. Single-Board RIO Device with Daughterboards

The PID system implements control of the piezo actuator. The low-voltage board continuously follows the strain gage signal (process variable of the PID system) to accurately control the piezo actuator according to the feedback signal. Developed daughterboards implement three-channel data acquisition, signal generation for control of the piezo actuator, onboard high-voltage power supply generation, signal amplification for the actuator, and control of sixteen 24 V optically isolated digital I/O.

One reason we chose NI hardware was the ability to build the software application using the LabVIEW graphical programming environment, which helps create easily configurable applications in a short time. We developed the application using LabVIEW software, the LabVIEW Real-Time Module, and the LabVIEW FPGA Module. We used the LabVIEW FPGA Module to implement PID control of the actuator and data acquisition. We used the real-time part of the software for data conversion, implementation of measurements and logging, transfer of configuration data to FPGA, and transfer of measured flow properties of the liquids to the host application for real-time representation.

Solution Benefits

Our solution delivers functionality in a small form factor and can work continuously over long periods of time. The powerful FPGA of the Single-Board RIO allows data processing, waveform generation, and PID control of the actuator with the highest possible accuracy and speed, thus increasing the system’s efficiency.


We used NI technologies to provide the product owner, Rheology Solutions, with a hardware platform that satisfies requirements and can be used for continuous monitoring of flow properties of liquids in the pipe in real time. The system is successfully installed and running in various food production plants in different parts of the world.

Author Information:
Rafayel Ghasabyan
Find this author in the NI Developer Community

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