DC Electronic Load Applications and Examples Application Note V 3032009 22820 Savi Ranch Parkway Yorba Linda CA, 92887-4610 www.bkprecision.com Table of Contents INTRODUCTION.........................................................................................................................3 Overview of software examples........................................................................................................3 POWER SUPPLY TESTING.......................................................................................................4 Load Transient Response.................................................................................................................4 Load Regulation................................................................................................................................5 Current Limiting................................................................................................................................6 BATTERY TESTING...................................................................................................................7 Battery Discharge Curves.................................................................................................................7 Battery Internal Resistances.............................................................................................................8 PERFORMANCE TESTING OF DC LOADS...........................................................................10 Slew Rate.......................................................................................................................................10 OTHER DC LOAD APPLICATIONS........................................................................................12 Voltmeter........................................................................................................................................12 Fuse...............................................................................................................................................12 SOFTWARE EXAMPLES.........................................................................................................12 Battery Discharge Test....................................................................................................................13 Voltmeter Reading..........................................................................................................................15 Fuse Application.............................................................................................................................15 Reference.................................................................................................................................16 in the later sections utilize INTRODUCTION B&K Precision's DC load model Unfortunately, the software 8500 as part of the different files are supported only for setups and test configurations. Windows platforms. However, Most applications can be due to the excellent cross- simulated in the same fashion platform capabilities of with other brands of DC loads, As technology is constantly python, some users may be with the exception of all the advancing, demands for able to get the library (which software examples. They are quality test instruments does not have to be utilized written specifically for full increase due to the need for via COM) working on other compatibility with B&K making better and accurate platforms. Please see the Precision's 8500 series DC measurements to library's documentation for loads and are not intended to accommodate newer more details. technologies. For most support other brands of DC electronic applications today, loads. In general, any measurements made with B&K using energy efficient and Although the software and Precision's equipments are reliable power sources is examples are written in typical, but not guaranteed. critical. For this reason, it is python, users who have other important to have a test particular preferences in terms instrument that can accurately Overview of software of the programming language portray results that define the examples to use can easily use the COM performance of the power library provided in the sources used to provide software package to write electricity for devices such as Throughout some of the similar examples in the electrical vehicles, computer sections in this application language of their choice. power supplies, 3G cellular note, software examples are Some languages that have phones, and even consumer provided to enhance and been found to work well with standard household batteries. simplify test methods as well the COM library are Visual Programmable DC Electronic as to bolster features of B&K Basic and Visual C#. Other loads are one such instrument Precision's 8500 series DC languages are also expected that will aid in testing various loads that can be controlled to work with the library, given settings, configurations, remotely with a PC computer the correct declarations and schemes, and methodologies. via RS-232 interface. Unless modifications within the The intention of this otherwise noted, all examples program. application note is to provide a are written in python general scope of a DC load's programming language. They usage. Some standard also require two python performance tests for testing libraries and the 8500 DC load power supplies will be COM library installed on the PC described in details. used for communication in Furthermore, several methods order to operate correctly. To for testing the DC load itself obtain all these as well as will be included in the later instructional documentation sections. Additional details on for installation and setup, practical DC load applications please visit one of our DC load and setup information are product pages at: provided as a source to assist http://www.bkprecision.com/p in performing various test roducts/categories/sub_catego setups and measuring data. ries/models/? As a note, all applications and model=8500#software. software examples contained 3 of 17 POWER SUPPLY TESTING For design testing and verification, the need for regulated power supplies are increasing with ongoing advancement in technology. More so, it has become a necessity in newer electronic devices to be tested with precise and sophisticated power supplies. There are some specifications that determine some underlying performance factors in typical power supplies. Particularly, Figure 2. Transient Response for B&K Precision 9130 the load transient response, load regulation, and current limit. In the following are ignored, and therefore the load current. In order to sections, each of these factors results may vary and may not verify the response, are addressed as an example reflect exactly what is shown measurements of the rise and to describe and demonstrate in the following sections. fall times upon a step change the setup, configuration, and in the load is necessary. Generally, this type of test equipment required for testing Load Transient and verification. Each requires a load that is able to example will utilize B&K Response produce a rise and fall time Precision's 8500 DC load as approximately five times part of the setup. An important element to faster than the power supply. power supply testing is a The following application Disclaimer: The following measurable unit of load demonstrates an effective sections include general transient response, which approach to testing the load setups with some settings characterizes the capability of transient response of a B&K specified for the test the power supply to stabilize Precision power supply model environment. Some details itself upon a step change in 9130. Power Supply DC Load Settings: 5 V Mode: Transient Trigger: Pulse 0.1 A to 3.0 A Digital Oscilloscope Limit: 3.1 A Trigger: negative slope + - + - Figure 1. Load Transient Response Test Setup 4 of 17 Objective transient response is observed to the rated current load of during the rise time in the load the power supply. Characterize the time it takes with a step change from 1.5 A for a power supply to stabilize to 3 A. The output voltage Approach its output voltage after a step dropped by approximately 1.6 change in the load. mV. Use a DC voltmeter to measure the voltage change Approach when the DC load is used to step the power supply from 0 Connect a DC load (B&K Load Regulation current to rated current. Precision 8500 DC load) to a power supply. Use the DC load's transient mode to apply Load regulation is another Setup a step change in load to the important element when The measurement is power supply. testing a power supply. It is a performance measurement conceptually simple, but it is that requires setting the power critical that the voltmeter Setup supply to its rated voltage. To used to measure the voltage be specific, the test for change is connected to the A B&K Precision 9130 power measuring this element is output terminals of the power supply was set to 5 V output based on measuring the supply independently of the with the current limit set to 3 output voltage levels of the leads used to connect to the A. A B&K Precision 2542 supply when a load connected DC load. Failure to do this will digital oscilloscope was used to it changes from zero measure the contact to view the power supply's current to rated current, which resistance of the power leads, output voltage. The scope differs depending on the overestimating the load was AC coupled and set to model used under testing. regulation and output trigger