Red Seal Instrumentation and Control Technician flashcards
Red Seal Instrumentation and Control Technician · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Lockout/tagout
- A procedure that isolates all energy sources, verifies zero energy, and applies a personal lock and tag before maintenance begins on an instrument loop.
- Intrinsic safety
- A protection method that limits electrical energy into a hazardous-area circuit so that no spark or heat can ignite the surrounding flammable atmosphere.
- Temperature class
- A T-code assigned to hazardous-area equipment that states the maximum surface temperature; it must not exceed the ignition temperature of the gas present.
- Arc-flash boundary
- The distance from energized equipment at which incident energy equals 1.2 cal/cm²; PPE selection is based on the energy inside this boundary.
- CAT rating
- A multimeter safety rating that states the maximum transient overvoltage the meter can withstand in a given circuit category, from CAT I to CAT IV.
- Loop calibrator
- A portable instrument that sources or reads 4-20 mA and often HART signals, used to stroke a valve or verify a transmitter without the control system.
- Calibration traceability
- A documented chain linking the calibration standard used to a national metrology institute, with an accuracy ratio of at least 4:1 to the device under test.
- Megohmmeter
- An instrument that applies a high DC voltage to measure insulation resistance; it must be disconnected from electronic instruments before testing.
- Ohm's law
- The relationship V = IR between voltage, current and resistance in a circuit; combined with P = VI it gives power in watts.
- 4-20 mA loop
- A current-loop signal in which 4 mA represents 0% and 20 mA represents 100% of span; a 250 ohm resistor converts it to 1-5 V.
- Cold-junction compensation
- A correction applied to a thermocouple circuit that accounts for the temperature of the reference junction so the reading reflects the measuring junction only.
- PT100 RTD
- A resistance temperature detector with 100 ohms at 0 °C; its resistance rises about 0.385 ohm per °C near ambient temperature.
- Differential pressure flow
- A flow measurement in which the square of the flow rate is proportional to the pressure drop across an orifice or venturi; square-root extraction linearizes it.
- Level by DP
- A level measurement using the hydrostatic relationship delta-P equals density times gravity times height; reference-leg fill and density must be known.
- Thermocouple
- A temperature sensor made of two dissimilar metals that generates a small EMF proportional to the temperature difference between its junctions.
- pH two-point calibration
- A calibration using two buffer solutions, typically pH 4 and pH 7, to set the slope and offset of a glass electrode.
- Valve Cv
- The flow coefficient equal to the volume of water in US gallons per minute that passes through a fully open valve at a pressure drop of one psi.
- Cavitation
- A condition in which the pressure at the vena contracta of a valve falls below the liquid vapor pressure, forming bubbles that collapse and damage the trim.
- Fail-closed valve
- A valve whose actuator spring drives it closed when air or power is lost; also called air-to-open.
- Valve positioner
- A device that compares the controller signal with actual stem position and adjusts actuator air to reduce friction and hysteresis effects.
- PID control
- A control algorithm whose output combines proportional, integral and derivative terms acting on the error between setpoint and measured value.
- Cascade control
- A control scheme in which the output of a primary controller becomes the setpoint of a secondary controller that regulates a faster inner loop.
- Feedforward control
- A control strategy that measures a disturbance and adjusts the manipulated variable before the error appears, usually trimmed by feedback.
- PLC scan cycle
- The repeated sequence of reading inputs, executing the program and updating outputs; its duration affects the response of the control loop.
- Dead time
- The transport delay between a change in the manipulated variable and the first measurable response; it limits the gain a loop can tolerate.
- Ziegler-Nichols method
- A tuning technique that finds the ultimate gain and period at sustained oscillation, then sets controller parameters from fixed ratios of those values.
- Bumpless transfer
- A switch between manual and automatic control in which the controller output tracks the manual value so the final element does not move abruptly.
- I/P transducer
- A device that converts a 4-20 mA electrical signal into a proportional 3-15 psi pneumatic signal for a valve actuator or pneumatic controller.
- Pascal's law
- The principle that pressure applied to a confined fluid is transmitted equally in all directions, so force equals pressure times piston area.
- Nernst equation
- The relationship giving the electrode potential of a pH cell, about 59 millivolts per pH unit at 25 °C.
- LEL detector
- A combustible gas sensor, often catalytic bead or infrared, calibrated so that alarms occur at a percentage of the lower explosive limit.
- P&ID instrument bubble
- A circle on a piping and instrumentation diagram containing a tag; a horizontal line through it means the instrument is field-mounted.