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Presentation on theme: "CURRENT RAMPING."— Presentation transcript:


2 Basics of Magnetism The atomic force that can attract or repel through space, air, solid matter. An invisible field (Flux) exists between the poles of a magnet This field can be used to act upon ferrous (iron) materials Even without direct contact, magnets can influence ferrous objects

3 Basics of Magnetism Each magnet has a north & south pole
Like poles repel Unlike poles attract

4 Magnetic Flux Invisible magnetic field is called Flux

5 Electromagnetism Interaction between electricity & magnetism
When electricity flows through a wire, a magnetic field is setup around the wire This field is weak, but can be detected by certain test equipment

6 Electromagnet Wrapping a nail with copper wire, passing current through the wire, magnetizes the nail The more wire & more current, the stronger the magnet field

7 Electromagnetic Induction
A wire carrying electricity produces an electrical current in an other wire. The flux around the current carrying wire induces a tiny electrical current in the second wire Passing a wire through a magnetic field will induce a voltage in the wire. The flux will act upon the free electrons in the wire to produce electricity Ignition Coil

8 How a Current Probe Works
The strength of the magnetic field around a wire depends on the rate of current flow This magnetic field induces a voltage within the probe tip. The voltage is converted to DC and amplified. The stronger the magnetic field the higher the voltage output from the probe.

9 Why use a Current Probe? With a DMM, the circuit must be opened & the meter inserted into the circuit With a current probe the circuit does NOT have to be disturbed! DMM’s only give a numeric value Current probes when used with a scope, give a graphic presentation of what is going on in a circuit

10 High Current Probe Measures circuits of 0 – 600 A
For every millivolt displayed on meter, is equal to One Amp ( .250v = 250A) Used for measuring large currents such as starter draw

11 Low Current Probe Measures circuits of 0 – 60 A Two settings:
1mV/10mA (100mV = 1A) – used for low current testing (max 10A) 10mV/100mA ( 10mV = 1A) – Used for high current testing (max 60A)

12 Here’s How it Works Scopes measure voltage not current
Current probes measure current & convert to voltage signals Simply clamp probe around circuit being tested Either wire will work, remember current is the same through out the circuit

13 The Basics Turn on probes, making sure battery is good
Connect probe to scope, select scale to be used, zero probe before it is clamped to wire Clamp probe around around wire w/ arrow in direction of current flow 10 mV Scale – for every 10 millivolts displayed on screen equals 1 amp 100 mV Scale – for every 100 millivolts on screen equals 1 amp

14 Current Ramping Gives a true picture of what is going on with in a circuit. In this circuit we see a gradual ramping of current as the injector is turned on. It indicates peak current & the shift to current limiting during the hold period

15 Ramp Time Is the time in milliseconds to reach peak current flow
In this illustration the current limiting section shows that the IC module can regulate max current to a safe & effective level. This test measures the coil dynamically & can help isolate a defective IC module We can also determine high resistance, low voltage & ground issues

16 Simple Measuresmensts
Current ramping a fuel pump circuit is the easiest and most effective way to look at the condition of a fuel pump Clamp probe where ever convenient

17 Fuel Pump Specs

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