FineSoft on
LabWindows/CVI Platform
LabWindows/CVI, from National Instruments, offers full ANSI C as the programming language. However, FineTest has written a Test Library, Instrument Drivers, and a Program Shell to make test program development very easy. You can write a test program with only a minimal knowledge of 'C'. LabWindows/CVI also has built in functions for creating user interfaces, controlling the serial ports, etc. which makes writing today's power supply test programs much easier.
These links will take you to each topic:
The Test Library is a compilation of all the standard tests performed on power supplies. It is very flexible and new tests can be added as they are developed. This library can also be customized for different families of power supplies. Selecting a test displays the following fill in panel to specify the parameters of the test.
Output Voltage Test
In this example, we want to test the power supply output voltage. The user must enter the low limit and the high limit for the test. Also entered is the matrix input number to which the power supply output is connected, and the test name for this output in the test results printout. This is all the user must enter to do an output voltage test, the sequence and instrument control is already written, saving the user's time and effort.
Line Regulation Test
In this example, we want to test line regulation. The user must enter the mux channel to connect to the DMM, the lower AC Voltage (Low Line), and the upper AC Voltage (High Line), and the AC Current Limit. Also entered is the maximum output voltage delta in mV, and the test name for the printout. As the user enters the values for these parameters, the command line on the bottom of the screen is automatically updated. This is all the user must enter to do a line regulation test, the sequence and instrument control is already written, saving the user's time and effort.
Hold-Up Time Test
This test measures the time from the removal of AC Input Power to the time the supply falls out of spec (below turn-off voltage). Note that from the time limit (Minimum Hold-Up Time), the proper horizontal scale for the scope is derived (see photo from scope below).
Program Shell (User Interface at Run-Time)
The following are the panels that are displayed to the operator at run time.
Program Verification
This first panel is Program Verification. This displays to the operator which test program is loaded and ready to run. It also shows the version number, revision, author and release date. There are also four more lines that can display more information if necessary. The operator must accept that this is the correct program before running or quit if it is not (ISO9000).
Test Information
The next panel displayed to the operator is the Test Information panel. This panel is used to collect specific information about a test run, and need only be filled out once at the beginning of the test run. Information entered here includes the Tester number (if more than one ATE is used on the line), the Fixture number (if more than one fixture is available), and the Part Number (if more than one part may be tested on the same fixture). The operator can also select whether or not to receive a printout of the whole test, a printout only if the unit fails, or no printout at all. The filename for the data log file can also be entered here, as well as enabling/disabling data logging. [Most users customize this and the next panel to fit their specific data collection needs]
Unit Information
After verifying that the correct program is running, entering information about the test run, and setting up printing/logging options, the operator now needs to enter information about the unit to be tested. The serial number of the unit to be tested, the operator's identification number, the test cycle of the unit to be tested (pre-burn-in, post-burn-in, final test, diagnostic etc.) and whether or not this unit is being retested.
The operator then clicks on the GO button and the unit is tested.
Pass/Fail Result
After the unit has been fully tested, a pass or fail result is displayed to the operator. The operator can now choose to either test another unit or stop testing. If the operator chooses to test another unit, the program returns to the previous panel, Unit Information, and a new serial number is entered and tested. This loop can continue until all the units are tested.
There is also a button to re-print the test results if needed (printer ran out of paper, ink etc.)
Interacting with the operator at run time
Message to the Operator
While testing a unit, it is often necessary to instruct the operator to perform some operation on the unit (turn on a breaker, turn off a switch etc.) This panel is the Message to Operator panel that allows the program to tell the operator what needs to be done and wait until the operator is finished.
Question to the Operator
This panel asks the operator a question and waits for a response.
Pot Adjustment
This panel is specifically designed for adjusting the output voltage of a power supply. As the voltage rises or falls, the bar graph in the center of the screen also rises and falls. When the output voltage is out of limits, the bar graph changes color from green to red.
Instrument Drivers are simple user interfaces that allow the user to control the instruments in the tester. Each instrument has a driver, and in the driver there are panels to control the functions of the instrument. Each function (sometimes a combination of functions) has a panel. Each panel has a command (or function call) associated with it.
Example Instrument Driver
The panel below is from an instrument driver for a DC Source. Notice that there are two input boxes to be filled in with values, VOLTAGE and CURRENT. Also notice the command DCS2_CONF on the bottom of the panel.
This panel will set the DC Source current limit to the value in the CURRENT input box, and then set the DC Source to the voltage specified in the VOLTAGE input box.
This panel also fills in the parameter values for the voltage and current in the command DCS2_CONF.
The user now has the option to run this panel immediately, or to insert the command DCS2_CONF (24,5) into the test program.
Using instrument drivers makes writing a test program very easy, as the user can execute a function and see how the power supply reacts to the change before inserting the command into the test program. After seeing that the unit under test reacts correctly, the user can insert the command into the program. This saves time in debugging the test program, as the user will have already seen how the unit under test reacts and verified that the test sequence is correct.
More Instrument Driver Examples
The following samples show how the instrument drivers control the instruments function by function.
Connect to DMM
This panel connects a matrix input to the DMM through the switching matrix. In the example, input number 5 is connected to the DMM.
DMM Configure
This panel controls the configuration of the DMM (Digital MultiMeter). On this panel, the setting for the range and resolution can be set.
DMM Measure
This panel takes the measurement from the DMM. The value is returned in the variable &MEAS that was entered in the input box.
Compare and Log Data
This panel is the Compare and Log Data panel. Along with instrument drivers for the instruments in the tester, FineTest has also written drivers for commonly repeated tasks needed to test a power supply. One of those tasks is to compare a measurement to its test limits. If the measurement is within the limits, the unit has passed the test. If the measurement is outside of the limits, the unit has failed the test. Along with comparing the measurement to its limits, this function also logs the measurement, limits, and pass/fail result data into an ascii data log file.
Instrument drivers make writing a test program very easy. The user can execute a command immediately and then, if happy with the result, insert the command into the test program. This greatly reduces the development time for a test program as the user is debugging the program as it is being written.
FineTest has taken advantage of the usefulness of the instrument driver, and developed drivers for other common necessary functions needed to test power supplies. This also greatly reduces test development time, as the user does not need to write the cumbersome overhead software that brings everything together.
Using the instrument drivers, and many years of experience testing power supplies, FineTest has developed a test library of common power supply tests. The tests have been reduced to simply panels that require only the minimum information needed to test the power supply. The test library greatly reduces the work required to develop a new test program, as the development of the proper test sequence and instrument control have already been done.
The Program Shell is an easy user interface and test executive combined. It allows for the verification of the program to be run, the gathering of information for data logging (tester number, fixture number, serial number etc.). It also has a loop to repeat the same test on different units one after the other. This shell is field proven and easily customizable to the user's current or desired data collection format.