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To develop a custom, fully automated test application for unit testing industrial grade chillers at the end of the manufacturing line. Water must be pumped through the chiller at a known, controlled rate while monitoring and/or controlling the following in real time:

  • multiple temperature readings
  • multiple flow rate readings
  • multiple pressure readings
  • control motor operated valves
  • monitor unit high voltage and current draw

Once complete, the application was required to perform analysis on the results, store all data to a MS Access database and print reports at any time after testing.


At the end of the manufacturing line, the chiller unit was positioned alongside a series of large, insulated tanks of water. The output of one tank would be connected to the input of the chiller while the chiller's output was fed back to the tank. The premise of the test was to pump water at a known flow rate through the chiller, with the chiller turned on, while monitoring the chiller's ability to effectively 'chill' the water in the external tank over time. Additionally, several run-time characteristics of the chiller needed to be monitored, analyzed and recorded during runtime to determine overall efficiency and functional behavior of the unit, ensuring it is operating within designed specifications.

  • Up to (10) temperatures were monitored via thermocouple inputs.
  • A total of (2) pressures were monitored (4-20mA signals).
  • software based PID loops were designed to control flow using paddle-wheel sensors (4-20mA signals) as feedback and Georg Fisher motor operated valves (4-20mA control signals) as the controlling variable.
  • High voltage and current values were recorded using Ohio Semitronics equipment and its RS-485 interface
  • National Instruments Fieldpoint for (1) monitoring thermocouple and presure inputs, (2) monitoring paddle-wheel feedback and (3) controlling motor operated valves.

Software timed PID loops were designed to allow the user to dial in a desired water flow rate. The application was capable of controlling up to (3) PID controllers simultaneously (three separate MOV's on three separate tanks).

All trending data was displayed on the user interface, proving instantaneous feedback during operation.

All data was ultimately stored to a secure, backed-up location on the server - both in the form of data files and directly dumped to a MS Access database via custom SQL code written in NI's database connectivity toolset.

Reports could be retrieved via two means - either the test application or a separate set of custom MS Access forms. Screenshots of both can be found below.

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