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Transoma Medical: PXI Based Electrical Test System for Animal Research Products
Products Used:
LabVIEW 6.0.2
TestStand 2.0
PXI - 100 8-Slot Chassis
NI 6508 digital I/O card
NI 5112 Scope Card
NI 6602 Counter/Timer Card
NI 8674 Embedded Controller
NI GPIB Card
NI SCB-100
NI SCB-68
The Challenge:
To automate the manual Electrical Test System for animal transmitters.
To minimize human intervention in conducting tests and to reduce test cycle times.
The Solution:
Creating an automated Electrical Test system using PXI, LabVIEW and TestStand.
The technology for monitoring and collecting physiological data from conscious, freely moving laboratory animals, is in great demand from pharmaceutical companies to academic research institutions. V I Engineering customer, Transoma Medical, is a world leader in the design and manufacturing of animal telemetric implants since 1985.
PhysioTel ® implants are available in a variety of sizes to accommodate various species varying from mice to cattle. Parameters measured include arterial pressure, left ventricular pressure, bladder pressure, kidney pressure, ECG, EEG, temperature, activity, as well as other user specific parameters. Every implant contains one or more sensors, plus a battery and electronics module. All models incorporate a magnetically activated on-off switch to conserve battery power in vivo or ex vivo.
Each implant undergoes a series of tests at different stages of production. One of the most important test groups each device goes through at different stages of production, is the Electrical Test group which is often repeated and includes the following major tests:
- Current
- Coil Voltage
- Period - Sync, Pressures, Shorted ECG, Thermistor Activity
- Noise Level
- Crosstalk
- Mode Detection
- Clipping
Electrical Tests on Animal Implants
Transoma Medical challenged V I Engineering to build an automated system to perform the specified Electrical Tests on a variety of products for different animals. The methods for data collection, analysis, and report creation needed to be highly automated, in order to reduce the risk of human error, reduce cycle times as much as possible, and to efficiently generate electronic test reports.
Transoma Medical relied heavily on operators with their legacy system. Data collection was performed using instruments varying from handheld multi-meters to radios. The operator was required to switch cables to complete different testing steps, manually change test conditions and calculations, and then keep a handwritten log of test results. When tests required data from a previous application, the operator had only the hand written records to rely on.
Automated Test System with PXI, LabVIEW and TestStand
V I Engineering developed a PXI-based test system with NI-SCOPE, NI-SWITCH, NI-GPIB and NI Counter Timer cards, using a perfect blend of LabVIEW and TestStand to provide a much needed flexibility and user-friendliness to the system. The GPIB card helped with the integration of many of Transoma Medical's existing measurement instruments.
The initial specifications required that 12 different products be tested on the new system, but Transoma required enough flexibility to allow for the addition of future models. Transoma built multiple, custom fixtures to hold products in specific positions for testing, in some cases touching certain points with po-go pins, and enclosing relays. These functions were controlled by NI-SWITCH to automatically change test conditions during the course of testing. A common fixture, connected to all others, contained a receiver and all the connections to the PXI-chassis.
LabVIEW and TestStand for Custom Software
LabVIEW was used to create code for setting-up instruments, changing test conditions, taking measurements, and editing steps. These VIs were called by TestStand steps. The user interfaces, where the test results, test conditions, and user messages are displayed, were also created in LabVIEW. The measurement values were communicated from TestStand to the LabVIEW user interfaces using the Queue structure.
All LabVIEW code, including the user interface were designed for reusability with all models. The user interface VIs were re-arranged at run-time depending on models, using Property Nodes to change captions, hide un-used indicators, or grey-out measurements that had not been performed yet. TestStand was used to easily re-arrange test events for efficiency, as well as performing different configurations of measurements for each production stage within a single sequence for each model.
Testing with the Automated System
To start testing, operators attach the unit to the testing fixture, then select the model and appropriate production, enter the serial number of the product and click "Accept Serial Number" (See Figure 2). If the production stage is one in which the product does not have a serial number, then the operator selects "No Serial Number" and the system automatically generates a number using the station number, the letters "NN" meaning no-number, and the next available number for this model.
The tests proceed in groups of related measurements where each group is displayed on a different UI. Since all switching, measuring, data analysis, and recording is performed by the system, the operator does not need to intervene. However, the operator is given the option to Abort or Repeat a test if necessary. If the operator is required to change a part, due to "out of spec" conditions, it is clearly indicated on the UI as a user message, and an input is provided for the operator to change component value (see Figure 3).
Finally, at the completion of a test sequence, a report is generated by TestStand and saved in a pre-determined location on the system. For tests that require data from previous tests, the system automatically locates and retrieves the needed information.
Benefits of an Automated System
Since all the labor of setting up instruments, switching cables, recording and analyzing data is removed, the automated test system is easier for the operators to use, which means less time is required for training. The automated switching, data collection and analysis reduced test cycle times up to 57%, increasing throughput, as well as improving precision and reliability of tests.
The flexibility of the system for future expansions, proved to be the most important feature, for Transoma Medical is always exploring new technologies to develop new products. The PXI-based system we provided was a cost effective and reliable system, adding value and integrity to a critical part of production, earning us strong relations with our rapidly growing customer.
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