ITI Technician Mechatronics (AITT Theory) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Lockout/tagout verification

After isolating and locking all energy sources, stored energy must be dissipated and a test performed to confirm zero energy before work begins. This prevents unexpected startup or release.

Arc flash boundary

The distance from an arc source at which incident energy equals 1.2 calories per square centimetre, the threshold for a second-degree burn. PPE is chosen from calculated incident energy.

Hierarchy of controls

Order of hazard control effectiveness: elimination, substitution, engineering controls, administrative controls, then personal protective equipment. PPE is the last line of defence because it protects only the wearer.

Noise exchange rate

For a 3 dB exchange rate, each 3 dB(A) increase halves the permitted exposure duration. At 85 dB(A) the limit is 8 hours; at 88 dB(A) it is 4 hours.

Third-angle projection symbol

The truncated-cone symbol with the small circle on the left identifies third-angle projection, where views are placed on the same side as the observer. First-angle shows the small circle on the right.

Hole-basis fit notation

A fit written as 40 H7/g6 uses a hole whose lower deviation is zero (H) and a shaft with clearance (g). The number is the IT grade defining tolerance width.

Micrometer least count

A metric micrometer with a 0.5 mm sleeve pitch and a 50-division thimble has a least count of 0.01 mm. Reading equals sleeve value plus thimble divisions times 0.01 mm.

Three-phase power formula

For a balanced three-phase load, active power equals the square root of three times line voltage times line current times power factor. Line and phase values differ between star and delta.

Silicon diode forward drop

A forward-biased silicon diode drops about 0.7 volts, while a germanium diode drops about 0.3 volts. This drop must be allowed for in low-voltage circuits.

Bearing L10 life

Basic rating life in millions of revolutions equals the dynamic load rating divided by equivalent load, raised to the power 3 for ball bearings or 10/3 for roller bearings.

Bolt torque formula

Tightening torque equals nut factor times clamp force times nominal diameter. The nut factor is roughly 0.2 dry and 0.15 lubricated, so lubrication greatly changes preload for the same torque.

V-belt wedge advantage

A V-belt transmits more torque than a flat belt of similar size because the groove sides wedge the belt, increasing friction. Belts must run in matched sets and correct tension.

Torque from power and speed

Shaft torque in newton-metres equals 9550 times power in kilowatts divided by speed in revolutions per minute. Power equals 2 pi times speed times torque.

Pascal's law

Pressure applied to a confined fluid is transmitted undiminished in all directions. Force equals pressure times area, so a larger piston area produces greater force at the same pressure.

Relief valve function

A relief valve limits maximum system pressure by diverting flow to tank, protecting the pump and components. It is set about 10 to 15 percent above working pressure.

Live zero 4-20 mA signal

Using 4 mA for the zero value allows a broken wire or failed transmitter to be detected, because a valid signal never falls to 0 mA. 20 mA represents full scale.

Pt100 resistance thermometer

A platinum resistance sensor with 100 ohms at 0 degrees Celsius. Resistance rises about 0.385 ohms per degree Celsius near zero, giving accurate, stable temperature measurement.

PLC scan cycle

The PLC reads inputs into an image table, executes ladder logic from top to bottom, then updates outputs. Scan time, typically milliseconds, determines response to fast events.

PID integral action

Integral action accumulates past error and removes steady-state offset. Too much integral gain causes overshoot and windup, so anti-windup limits are used when output saturates.

Induction motor slip

Slip equals synchronous speed minus actual speed, divided by synchronous speed. It is typically 2 to 5 percent at full load and increases with load.

Star-delta starting

The motor starts in star, reducing winding voltage and starting current to one third of direct-on-line values, then switches to delta for running. Starting torque is also reduced to one third.

Single-point analog grounding

Analog signal shields are grounded at one end only to prevent ground loops that inject noise. Power and signal cables are routed separately to reduce interference.

Fieldbus termination

Both physical ends of a fieldbus segment need terminating resistors matching the cable impedance. Missing or extra terminators cause communication errors and intermittent faults.

Tool centre point

The TCP is the point on the end effector used for programming motion. An inaccurate TCP offset shifts every programmed path and causes position errors.

Robot repeatability versus accuracy

Repeatability is the spread when returning to the same taught point; accuracy is closeness to the commanded point. Robots are typically far more repeatable than accurate.

Predictive maintenance

Condition-based maintenance uses vibration, thermography, oil analysis, and current signature to detect developing faults and schedule repair before functional failure occurs.

Unbalance vibration signature

Mass unbalance produces vibration mainly at one times running speed in the radial direction. Misalignment adds two times running speed and axial components.

Half-split troubleshooting

Divide the system into two parts and test which half contains the fault, then repeat. This locates faults in far fewer measurements than checking components in sequence.

Mean time between failures

MTBF equals total operating time divided by the number of failures in that period. It expresses reliability for repairable equipment and supports maintenance planning.

SCARA robot configuration

Two revolute joints move in a horizontal plane and a prismatic joint moves vertically. SCARA robots are fast for pick-and-place but have limited vertical stiffness.

Robot wrist singularity

A configuration where two wrist axes align, requiring very high joint speeds for small Cartesian motion. Straight-line programs through singularities should be avoided.

Vacuum gripper selection

Vacuum grippers suit flat, non-porous parts and apply uniform force without marking. Porous or rough surfaces leak air and require high flow or alternative gripping.