Author(s):
Andre Lalonde -
Honeywell International Inc.
We need to perform a series of tests on our detector devices during design engineering phase. Because we have no additional funds for immediate mechanical handling and test automation, we need a considerable number of manual test stations. The two main processes to perform the test adequately are (1) equipment calibration, and (2) device under test (DUT) characterization. In order to perform the DUT characterization, all equipment we use for this process must be at the station at all times. However, the setup for equipment calibration only needs to be present at the beginning and can remain idle for the test period. We can use the equipment calibration setup at every station via a versatile communication method and greatly reduce cost.
Our solution is to equip a PC test station with GPIB and PCI test instrumentation and communicate with the mobile equipment used for system calibration via Ethernet (with possibilities for wireless Ethernet). For this solution, we were mindful of budget considerations, test speed, development time, and ease of programmability.
System Description
Most data communication detectors on the market have embedded trans-impedance amplifiers (TIA) to convert the photodiode current to a differential output voltage. There are four pins - Vout Q (inverted), Vout (non-inverted), power, and ground. For this particular DUT, we need to perform the tests at a high frequency because the TIA has a low frequency cutoff.
The test stations incorporate a LabVIEW Run-Time engine with NI-DAQ, NI-VISA, and the NI-488 driver software. We also used the PCI-5401 arbitrary waveform generator, PCI-GPIB for bench instrumentation communication, and the PCI-6034E data acquisition (DAQ) board for testing the DC equivalent of the RMS output of the detector. The GPIB Controller communicates with the laser current source and the DUT power supply. The laser source current and the modulation amplitude (PCI-5401) are actively iterated based on the reading from the calibration equipment (Ethernet).
Once the equipment calibration station has found the appropriate levels, the station’s LabVIEW program releases the instrument so other stations may use it. Presently, we are planning to share this "roll-around" setup among four stations. It takes mere seconds to calibrate a station. For this short time period, the equipment is "reserved." There are multiple Ethernet drops at our present location to make this task feasible. Presently, we are planning to move to wireless Ethernet to harness the potential of a "roaming instrument."
We perform these main series of tests in a production environment involving:
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Icc DUT series current, measured via the GPIB
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Vout Q and Vout - single-ended voltage with no light present on the photodiode with PCI-6034E
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VDIFF - differential voltage with no light present on the photodiode with PCI-6034E
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Responsivity of the TIA with light present, with PCI-6034
Once all tests pass, the part is binned accordingly. We save data for every part through various lot numbers in production for later traceablity.
Test Parameters and Data Storage
To create a cost effective method to store test parameters and efficiently import them into the test program, we created a database. Using the LabVIEW Database Connectivity Toolkit, the test program reads all parameters from the network and stores them in a global named cluster in LabVIEW, enabling us to use the VIs everywhere in the program. Therefore, the programmer can easily alter the program if we add a new test in the future.
Because there are thousands of parts to test for every lot, the data from every part is searchable by its respective work order number. The LabVIEW program is responsible for this process. Also, we can easily import all part data into a spreadsheet program and perform any mathematical manipulation necessary.
Human-Machine Interface
In order to meet production requirements, we need an easy-to-use HMI. It must have security features, such as user identification, and must also have an easy-to-use selection panel for the few variables needed to test the lot such as location, part number, and work order details.
The test panel must be simple so a user of any education level can operate it. We need to display all the test information, so the user can see details on DUT performance.
Cost Savings and Ease of Implementation
A typical calibration system to verify our test setup typically costs more than $15,000 (USD). Because we will be implementing up to four or five stations, there is an immediate cost savings of at least $45,000-$60,000. With an easy-to-use programming language, such as LabVIEW, and Ethernet and PCI-based test instrumentation, we can achieve significant savings.
Because the PCI-5401, PCI-GPIB, and PCI-6034E are all NI products, the integration with LabVIEW is straightforward. Using the PCI bus for communication with signal generation and DAQ equipment makes test time reduction easier than with standard bench test equipment. Using NI-VISA and its hardware communications flexibility, we can easily communicate standard GPIB commands to an Ethernet-enabled device increasing the power of the test system without the hassle of cable conventions and limited addresses.
The Ethernet Enabled AC Test system can share a mobile test system between PC test stations for cost savings up to a tangible $60,000 (USD). Also, with LabVIEW and PCI-based NI test instrumentation, we can integrate the flexibility of programming in G with speed improvements over standard bench-type test equipment. The ability to use prepackaged software toolsets, such as the LabVIEW Database Connectivity Toolkit, mean we can reduce the cycle-time it takes to release a test system.
Author Information:
Andre Lalonde
Honeywell International Inc.
830 E Arapaho Rd.
Richardson, TX 75081
United States
Tel: (972) 470-4485
Fax: (972) 470-4504
andre.lalonde@honeywell.com
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