Fuel injector oscilloscope pattern download#

Some circuits that have a square wave type of typical wave form may display the voltage decaying at the end of the switching period Fig 22.This voltage is generated by the component and can normally be ignored. Some circuits operating solenoid components, for example idle speed control devices, may display voltage spikes Fig 22, when the circuit is switched off.If the pattern is too low decrease the voltage scale. Therefore if the oscilloscope pattern is too high (or the upper part is missing) increase the voltage scale to obtain the view required.For alternating current (AC) circuits this will depend on the speed of the signal generator, for example, an inductive crankshaft position (CKP) sensor's output voltage will increase with engine speed.For direct current (DC) circuits this will depend on the voltage being switched, for example, idle speed control device voltage will be constant and will not vary with engine speed.The amplitude or overall height of the pattern (the voltage) Fig 22 & Fig 23, will depend on the circuit's operating voltage.Typical wave forms indicate the approximate position of the wave form in relationship to the 'zero grid', but this may vary fig 22, dependent on the system being tested and may be positioned anywhere within the approximate 'zero range' Fig 22 & Fig 23.The interpretation of this trace can be greatly assisted by reference to the typical wave forms illustrated in this chapter.

Currently available oscilloscopes are easy to connect and use, enabling a trace to be displayed on the screen without any specialist knowledge or experience.If the wave form displayed is satisfactory this is a reliable indication that the whole system is operating correctly. By watching the oxygen sensor signal with an oscilloscope any irregularity in the overall system performance can be detected. The complex electronic engine management systems fitted to catalyst equipped vehicles are designed to maintain the mixture level between quite close tolerances so that the oxygen sensor is able react to small changes in the exhaust oxygen level and feed this information back to the ECM in the form of a voltage signal.The oscilloscope can also be used to check the overall condition of an engine management system equipped with a catalytic converter, by monitoring the activity of the oxygen sensor.Once the cause of a problem has been diagnosed and rectified, the repair can be verified by retesting with the oscilloscope.When necessary, the response time can be slow enough to display signals such as the throttle position sensor. This fast response time enables diagnosis of intermittent problems and also enables the effect of disturbing parts of the system to be observed.It is easy to connect (normally just two leads) and the speed of sampling can be far in excess of even the best of digital multi-meters.The oscilloscope display can show the amplitude, frequency, pulse width, shape and pattern of the signal received, by effectively drawing a graph of voltage (vertically) and time (horizontally).

Fuel injector oscilloscope pattern download#

Usually it is possible to store wave forms and associated data in an internal memory and then print out or download the information onto a PC, enabling the scope patterns to be studied in detail.

They can also be used inside the car, while the vehicle is driven, to capture dynamic data.

Most oscilloscopes designed for automotive use can be hand-held and are therefore ideal for use in the workshop.

Unlike older analogue oscilloscopes dedicated to HT ignition testing, a modern digital oscilloscope has a variable voltage scale, enabling low voltages (typically 0-5 V or 0-12 V) to be displayed and also an adjustable time scale, enabling any wave form to be displayed in the ideal manner.

Digital multi-meters are entirely satisfactory for checking circuits in a static condition and for instances where any change in reading is a gradual one, but for dynamic checking and the diagnosis of intermittent faults, the oscilloscope is a very powerful workshop tool.

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