Wet Loop Test System

Industry: Consumer Products & Manufacturing


Donaldson Company Inc. provides industrial filtration solutions to a variety of markets. To quantify the performance of the company's filters, they are tested to the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) specifications to determine how efficient the filter is at removing particles of various sizes. To further stress the filters during testing, the environmental conditions need to be widely varied from 50 to 90 °F, 20 to 98% relative humidity, and 600 to 3000 cfm airflow. The previous test bench used by Donaldson Company was undersized and not capable of achieving the high or low extremes of many of the test specification requirements. Additionally, as the ASHRAE test standard evolved over time, the old system approached its usable life span.


Donaldson Company Inc designed a test fixture capable of meeting the ASHRAE standard, and leveraged Optimation for system control and data logging. The new fixture contains over thirty IO points, nearly double of the old system, virtually all of which need to have custom scaling and alarming parameters. To precisely maintain temperature, relative humidity and air flow set points, Optimation utilized a National Instruments cRIO 9022 controller.

Software written by Optimation in LabVIEW allows the system to maintain temperature to within ±5°F, relative humidity to within ±5%, and air flow to within ±2% of the set point between 630-3125CFM.This is accomplished using four PID software loops and controlling devices with a 4-20mA, a 0-10VDC, and two ModBus signals. Each of the four PID loops are easily configurable from the HMI allowing authorized users the ability to disable individual PID loops and manually control the device, change the system set point, and adjust the P, I and D coefficients to tune each control loop. In addition to controlling third party devices via ModBus, critical test information is also collected from third party devices using ModBus over Ethernet, RS-485, and RS-232. This data is combined with 4-20mA analog inputs and 0-10VDC inputs to be logged at a user configurable rate, as well as displayed to the user on the HMI. The HMI also includes a data trends graph for each of the inputs and is capable of displaying a virtually indefinite amount of historical data by bypassing the HMI's memory and utilizes an incredibly fast disk IO to display the trends.


Utilizing Optimation's integration services, Donaldson Company Inc. now has an air filter test bench capable of maintaining the most stringent control requirements. Tests can now be run without human interaction beyond the initial test setup while ensuring the safety of personnel and property by continually monitoring for out of range conditions.
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  • Consumer Products & Manufacturing

  • Control Panel Fabrication
  • Mechanical Engineering
  • Software Engineering

  • Continuous Control
  • Low Medium High Voltage
  • Test Systems

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