Printer-friendly version
Glossary of terms you will come across during your Phase 2 training.

Browse the glossary using this index

Special | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O
P | Q | R | S | T | U | V | W | X | Y | Z | ALL

Page: (Previous)   1  2  3  4  5  6  7  8  9  10  11  ...  107  (Next)



The rotating shaft of a starting motor. Inside a motor, this shaft is free to revolve. Mounted on it is a commutator which allows us to pass electrical current to windings which are wrapped around the shaft. In the middle of the armature is a laminated soft-iron core.

Typical armatures.


Arsenic is a deadly poison and is used in doping semi-conductors to produce N-type material.

That is why it is important to be careful when handling old electronic components. They may contain traces of this arsenic.


Asbestos warning signExtremely harmful material formerly used in brake and clutch lininig material, now banned form use. You may still come across it in friction and other heat resistant materials (heat shields, insulation), so treat it with extreme caution.

As can be seen from the image below, when asbestos is viewed under a microscope, we can see that the individual particles are spear like, with sharp ends. When these particles of asbestos become airborne and are breathed in, they can embed themselves in the lungs. After a latent period of about 30 years, this can cause asbestosis, an inoperable disease which will result in death.

Asbestos fibres as viewed under a microscope


In the Baldoyle Training Centre, one of the two assistant managers, Aidan Owens, has responsibility for the CP Fitters' Section.


An astable square waveAn astable circuit is an electrical circuit that does not stay in one stable condition. If you were to monitor it with an oscilloscope, it produces a 'square wave', this is a digital waveform with sharp transitions between low (0V) and high (+Vs). Note that the durations of the low and high states may be different. The circuit is called an astable because it is not stable in any state: the output is continually changing between 'low' and 'high'.

Three possible states are:

  • Astable: Not stable in any state, output is constantly changing between on and off 
  • Monostable: Stable in one state, either on or off 
  • Bistable: Stable in either state, on or off 

During the induction phase of the course, you will be issued certain tools, Tools Issued on Repayment.

As of July 2012, the cost of these tools to you is €200. This sum varies from time to time, as the prices of the tools fluctuate.

The cost of these tools is deducted from your wages over the durantion of the course, working out at €10 to €15 per week.

If you already have some or all of these tools, no issue and no deductions will be made.

You can see the full lust of tools here


This is short for 1 atmosphere, or 101.3 kN/m2 (expressed in SI units), or 14.7 psi (expressed in Imperial Units).

One atm is atmospheric pressure, 2 atm is twice atmospheric pressure.

Don't confuse this term with bar. They both measure pressure, but they are not the same.

1 bar = 100 kN/m2 = 14.5 psi

1 atm = 101.3 kN/m2 = 14.7 psi


Pressure is defined as Force per unit Area.

In the SI, Force is measured in Newtons, and area is the product of multiplying a distance (length) by a distance (breadth), metres x metres to give us a basic area of 1 square metre (1m2).

So, the basic unit of any pressure is 1N/m2, also known as 1 Pascal, or 1Pa.

This is a very small unit of measurement for practical use, so when we discuss much larger pressures such as atmospheric pressure, we talk in terms of thousands of Newtons of force, or kN.

Standard Atmospheric pressure is 101.3 kN/m2. We know that atmospheric pressure is constantly changing, and any figure above this is deemed to be high pressure, and any figure below this is deemed to be low pressure.

Within the earth's atmosphere, we have air. Although we are not normally aware of this, air has weight. This weight of air exerts a downward force on the surface of the earth.

As we gain altitude, the column of air above us gets shorter, and so exerts less force on us.

Force, acting on an area, is, by definition, pressure. In the SI, force is measured in Newtons, and area is measured in m2. For convenience, we measure pressure in milliBars. Check out the animation and see how the atmospheric pressure drops from the normal at sea level (1013mb) to lower and lower figures as we gain altitude.

Flash video(Flash animation)


This is fuel that has been broken up into extremely fine particles (in a diesel engine, this is done by the injectors). The reason why fuel is atomised is to have a relatively large surface area for each atomised particle of fuelFlash video(Flash animation)

The only part of any fuel that burns is its vapour. The amount of vapour given off by a fuel is directly proportional to its surface area. If we had one large particle of fuel, this gives us a relatively small surface area. If we take the one big particle, and break it up into thousands of tiny individual particles (atomise it), then there is a huge increase in surface area.

This in turn helps the fuel vapourise, which, in turn helps the fuel to burn.


A typical attenuatorAn attenuator is an electronic device that reduces the amplitude or power of a signal without appreciably distorting its waveform.

An attenuator is effectively the opposite of an amplifier, though the two work by different methods. While an amplifier provides gain, an attenuator provides loss, or gain less than 1.

The PicoScope PP198 shown is a passive 20:1 attenuator. This means that a 20V signal at its input will appear as a 1V signal on the output. As the signal is attenuated, the PP198 allows voltages of up to 300 V to be measured. This particular attenuator has been designed to allow fuel injector and primary ignition waveforms to be measured using the PicoScope automotive kit.

Attenuators are usually passive devices made from simple voltage divider networks. Switching between different resistances forms adjustable stepped attenuators and continuously adjustable ones using potentiometers. Fixed attenuators in circuits are used to lower voltage, dissipate power, and to improve impedance matching. In measuring signals, attenuator pads or adaptors are used to lower the amplitude of the signal a known amount to enable measurements, or to protect the measuring device, say, for example, an oscilloscope, from signal levels that might damage it.

More about attenuators from Wikipedia


Page: (Previous)   1  2  3  4  5  6  7  8  9  10  11  ...  107  (Next)