The Challenge:

Developing an Automated Test Equipment to perform endurance tests on up to 7 glow plugs simultaneously. Various parameters including voltage, current, temperature and status of the glow plug are to be monitored during the test.

The Solution:

Building a system that calibrates and controls the voltage of power supplies, switches on air-jet cooling and monitors the voltage, current, temperature and status of up to seven glow plugs during the endurance test. Recording the various parameters and initiating safety shut down when necessary are also provided. This system is accessible on the network and hence other users can view the logged data. Uses FieldPointä distributed I/O modules and LabVIEW software

Introduction:

The Glow Plug Endurance Test System (GPETS) used to test the endurance, durability and the life of 7 glow plugs at a time was developed using LabVIEW. To control the process and acquire the voltage, current, and temperature of the glow plugs Field Point Distributed I/O Modules are used. In emergency conditions like over voltage, over current, short circuit, high temperature of fixtures, high temperature of glow plugs, etc the system is automatically shut down using the watchdog features of Field Point. The system automatically recovers from power shutdown to complete the balance of any incomplete tests. Test data can be viewed from any computer on the network.

Application:

The Glow Plug Endurance Test System (GPETS) is used to test the endurance, durability and the life of the glow plugs. The glow plugs are used in diesel engines for starting of engines at low temperatures, reducing the pollution content of the exhaust gas, and ensuring smooth running of the engine immediately after starting at low speeds. The GPETS accelerates the endurance process cycle of the plug. The data acquisition and control of the GPETS is done using National Instruments FieldPoint distributed I/O modules and LabVIEW software

LabVIEW has the flexibility to control the process of the GPETS and acquire data for the test conducted for several thousands of cycles. The PC is connected to National Instruments’ Field Point Network module the Distributed I/O modules have the flexibility to control the entire process and acquire data of voltage, current, and temperature. In emergency conditions like over voltage, over current, short circuit, load shedding, high temperature of fixtures and high temperature of glow plugs, the system is automatically shut down as a safety measure.

Hardware Design:

The system consists of a Personal Computer, FieldPoint modules, FP1001 for networking from a remote location, FP-AO-210 for controlling the voltage, FP-AI-100 for acquiring the voltage, FP-AI-110’s for acquiring the current and temperature (from pyrometer), FP-TB-10 with FP-DI-AC240 and FP-DO-AC240 for checking the mains power supply and each regulated power supply, FP-RLY-420 for switching ON the power supply and FP-RTD-122 for acquiring the Jig-temperature. The detailed block diagram is shown in figure 1.

We chose National Instruments’ LabVIEW software for developing the GPETS. The individual tests were a collection of similar tasks, thus it was evident that the code should be modular. Each task was written to be self contained, generic sub-VI. Through the use of these software modules and a style of programming in LabVIEW called state machines, we developed different tests. With one test written and debugged, additional tests could be developed easily. With LabVIEW’s graphical interfaces, we were able present in data in good graphical format and control options to user in an easy to use, understandable manner.

GPETS has four main sub-VI’s -Voltage Calibration, Current Calibration, Data Entry, Type Program Execution, these four VI’s are opened in a sequence and the main panel of this application is the Type Program Execution.

The Voltage and current Calibration sub-VI controls the voltage and current for pre-defined input voltage and current this helps calibrate the acquired output voltage and current and also calibrates the power supplies to the required voltage and current. These values are then stored in the hard disk.

The Data Entry sub-VI is to set the parameters for the endurance test including controlling voltage for the working of the glow plug, ON duration, natural cooling time, forced cooling time of plug by air jet, the number of operations, the warning temperature set point, the warning current set point and number of power supply required.

The Type Program Execution sub-VI is to View the user specified data, Start the Endurance program (of different types) required for the glow plugs, to On-line Analysis of the present status of the seven glow plugs currents, voltages and temperatures and the process. Data logging of the date, time, number of cycles, voltage, current, and temperature with respect to time.

Type Program is in a sequence, which sets to a Plug Voltage for plug ON duration, and cooling time and the whole process is repeated for the number of cycles .The DC sources can be enabled or Disabled according to the need for the test i.e. no. Of plugs connected. The status of the glow plugs status can be known, i.e. whether it's working, not working or whether it’s not used. The present status will show the present voltages, currents, fixture temperature, pyrometer temperature, cycle of operation and the process undergoing and the warning indicator for the fixture temperature, pyrometer temperature and warning current. On-line plotting of Voltage Vs Time, Current Vs Time and temperature Vs Time graphs for seven glow plugs. The logged data for seven glow plugs voltage, current and temperature are logged to a database. The old test data can be viewed from the history of type programs. Automatic shut down in case of failure of PC communication

Conclusion:

After running many tests, this system has proven to be a very useful tool for testing the endurance, durability and the life period of the glow plugs. On the new LabVIEW system testing of the glow plug is done automatically for 3-4 week with out human intervention with features of automatic shutdown in case of emergencies and re-starting operation after power failure. All this at one-fifth the cost of a dedicated system.