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Design test systems to test and configure an HVAC product. Testing consists of verifying connection to unit devices as each device is installed and verifying factory wiring to unit compressors and fans. Configuration consists of downloading data to intelligent devices and main processor per unit sales order information. The number of test systems is to be driven by factory DFM/DFT practices.
The customer plans to re-design other product lines to use the same hardware and communication protocol as this product. Design such that common elements may be implemented in future designs.
The products are assembled globally. As a result, the design must provide a means for the end-user to edit messages displayed during testing to be in the language of their choosing.

To keep the mean time between stations on the assembly line consistent, two test systems were required.
The first system consists of verification of the connection of each intelligent device to the communication bus and download of configuration data to that device. As the units can be as long as 80 feet, a large monitor is mounted above the unit and an RF keyboard device is employed to allow the operator to interact with the test application from anywhere on the unit.
Connection faults are detected after each device is installed using a PC-based digital multimeter and oscilloscope. A PLC provides the I/O to close contactors and apply/remove power and to switch signals to the digital multimeter and oscilloscope.
As the unit bus cable is subject to harsh factory conditions after installation, detection of intermittent shorts from the bus cable to the unit frame was desired. A DC ground fault monitor is used to detect intermittent shorts between power or communication supplied to the unit and ground.
The second test system consists of main processor download and verification of factory wiring to unit compressors and fans. As the product offering has varying input voltages and tonnages, the test system includes a custom multi-tap transformer and circuit breaker switchgear assembly to supply power to the unit. To prevent the operator from changing the transformer tap selection without first turning the circuit breaker off, a keyed interlock system is employed. Transformer taps and circuit breakers are equipped with auxiliary contacts that are used to verify that the correct tap and breaker have been selected before applying power.
Unit measurements are performed using a PC-based digital multimeter and oscilloscope. The design is consistent between both test systems.
A PLC provides the I/O to close contactors to apply/remove power and to switch signals to the digital multimeter and oscilloscope. It is also used to monitor system conditions.
As this test system provides high voltage to the unit under test, operator safety is paramount. The PLC controls all critical operations independent of the PC in the test system. Zero speed switches are wired directly to the PLC and are used to detect when voltage is supplied and to illuminate a red rotating beacon. A ground fault monitor is wired to the PLC and is used to immediately remove power upon a fault. A ground continuity monitor is used to verify that ground is connected prior to applying voltage to the unit under test. Hands-free opto-touch devices are used to verify that the operator is at the test station whenever power is applied.
Wire harnesses between the unit and the test system were designed to minimize connection time and prevent misconnection to the unit.

To prevent entry errors and minimize maintenance, the software utilizes the order entry data generated by sales offices to determine what devices are installed on a unit. When an order is placed by a sales office, a XML file is created for the unit. This XML file is placed on an FTP site that all testers access and is used to determine what devices to install, the test sequence to perform, and what configuration data to download.
A database contains all configuration data, available tests, test sequences, and operator messages required by the test systems. A user interface assists the customer in creating/adjusting test sequences, operator messages, and test system configuration (file path directories, FTP timeout parameters, etc.). As the configuration data is common between the test systems and the field service tool of the customer, a synchronization utility is used to retrieve updates from the field service database. As a result, database maintenance is kept to a minimum.
Test results are also stored in the database. Results generated by testing performed at subsystem manufacturers are retrieved via FTP and stored in the results database to provide a complete test record for the unit.
The common elements of the software consist of order entry, FTP access, unit device and test sequence generation, configuration generation, communication drivers for the unit-mounted intelligent devices and main processor, and the PC-based instrumentation. The common elements were implemented as objects to allow easy use in future product testers.
As the software is running, the operator is prompted to perform any necessary steps and upon a failure is presented likely causes of the fault. Upon clearing the fault the operator is prompted to indicate what was done. This information is stored in the database and may be used by production managers to determine areas of improvement in the assembly process.

The test systems have been very well received in the factory and are a vast improvement over previous test systems. The customer has applied for three separate patents on the test systems; the device installation and communication bus monitoring process, the order entry/FTP process, and a fixture to provide error-free, easy connection to the compressors of the unit under test. OMNI is listed as a designer in each of the patent applications.
The software design has provided the customer with an easy means to maintain the latest configuration data. The common elements are being used in other product lines currently under development. The projected cost savings is significant.