ELECTRICAL SYSTEMS DIAGNOSTICS Electronic Specialties DECEMBER 2016 | ELECTRICAL TESTING SUPPLEMENT | 11 Oscilloscopes/lab scopes/ waveform viewers As a general rule, this category of tools will provide the most complete set of data, in most cases, when testing the functionality as well as the amount of current going to and through a circuit. Many accessories are also available for additional tests such as pressure transducers, ignition adapters, etc. The benefi ts of using a scope or waveform viewer include the ability to: · Adjust both the time and measurement scale to view the circuit · Observe more than one circuit at a time · Record waveform for comparison or future use · Observe history and catch glitches (intermittent issues) · Purchase and/or use accessories, such as pressure transducers, ignition adapters, etc., that can perform additional tests Some drawbacks to using a scope or waveform viewer include: · Additional time needed to set up tool After familiarity with the process, this takes less time · An initial investment that may be considered expensive Pico Technology Hickok/Waekon Digital multimeters (DMMs) These tools are very good for measuring specifi c values such as voltage, amperage, resistance and pulse width. Consider these tools as viewing a snapshot, while a lab scope is a video of an event. Benefi ts of multimeters include: · Relatively inexpensive · Fast test results · Portable · Various test leads and adapters available · Able to test high-voltage hybrid vehicles (with appropriate test leads and meter classifi cation) Drawbacks of multimeters include: · The readings given are digitized and are an average of the represented value, versus an exact value · Diffi cult to capture intermittent issues Scan tools Scan tools can be used to observe data the vehicle’s computer modules are producing. This can be useful to quickly determine if normal voltages are present on many components at the same time without the need to connect a tester to each individual component. Graphing capabilities are available to obtain readings over a period of time and to compare multiple data graphs simultaneously. Benefi ts to using a scan tool for electrical system testing include the ability to: · Quickly obtain and compare multiple values in digital format · Quickly obtain and compare multiple values in graphing format · Observe data without intrusion into connectors or wires · Observe data from multiple modules Drawbacks to using a scan tool for electrical system testing include: · Data interpreted by the PCM and tool may be different from actual measured values · Depending on the quantity of PIDs observed, data may not be “live” · Due to slower update rates, scan graphing values are not as precise as a lab scope Snap-on Diagnostics Continued on page 12 »
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