ISA CCST Level I flashcards
ISA CCST Level I · 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.
- Span
- The difference between the upper and lower range values; a transmitter ranged 0–100 psig has a span of 100 psi, and 20 mA corresponds to 100%.
- Zero shift
- An error in which the output at the lower range value is offset while the span stays correct; it is removed by adjusting zero at 0% input.
- Hysteresis
- The difference between output readings taken at the same input when approached from increasing and decreasing directions; found by running upscale and downscale passes.
- Five-point calibration
- A check at 0, 25, 50, 75 and 100 percent of span in both directions; the downscale pass exposes hysteresis and repeatability problems.
- Test uncertainty ratio
- The ratio of the reference standard's accuracy to the accuracy of the device under test; 4:1 is the commonly required minimum for a valid calibration.
- Pt100 resistance change
- A Pt100 RTD reads 100 Ω at 0 °C and changes about 0.385 Ω per °C, so roughly 138.5 Ω corresponds to 100 °C.
- As-found data
- Readings recorded before any adjustment; they document the drift since the last calibration and show whether the device was within tolerance.
- MTBF
- Mean time between failures, equal to one divided by the failure rate; used to set preventive maintenance intervals and spare-parts holdings.
- Availability formula
- Availability equals MTBF divided by the sum of MTBF and MTTR; reducing repair time raises availability as effectively as reducing failures.
- Lockout tagout
- An energy-isolation procedure in which every energy source is isolated, locked, tagged, and then verified at zero energy before work begins.
- Downscale drive
- A transmitter output forced below 4 mA, typically about 3.6 mA, to signal that the device has detected an internal fault or sensor failure.
- Breaking the loop
- Measuring loop current directly requires opening the circuit and placing the meter in series; measuring voltage across a known resistor avoids breaking it.
- Substitution test
- Applying a known mA signal at the transmitter terminals; if the control system indicates correctly, the fault lies in the field device or its wiring.
- Ground loop symptom
- Noise, offset or drifting readings caused by a shield grounded at more than one point; corrected by single-point grounding of the shield.
- HART communicator resistance
- A HART communicator needs at least 250 Ω of loop resistance between its connection point and the power supply for reliable digital communication.
- Voltage across 250 ohms
- At 4–20 mA a 250 Ω resistor drops 1–5 V, so measuring this voltage lets you infer loop current without breaking the circuit.
- Live zero
- Using 4 mA to represent 0% of range so that a failed loop reading 0 mA can be told apart from a genuine zero process value.
- Mechanical completion
- The state in which all equipment is installed and documented, with punch-list items closed, before power, air, or process fluid is introduced.
- Loop folder
- The document set for each loop: instrument index, datasheet, calibration certificate, loop drawing, and completed test records.
- FAT and SAT
- The factory acceptance test is run at the vendor's works before shipment; the site acceptance test confirms installed performance at the plant.
- Hazardous area verification
- Confirming the installed device's certificate, gas group and temperature class match the area classification drawing before energizing it in a classified location.
- Pump bump test
- A brief jog of the motor to confirm rotation matches the pump arrow before the coupling is installed and the unit is started.
- Commissioning sequence
- Mechanical completion, then loop checks, then functional tests, then dry and wet commissioning, then performance testing of the completed system.
- Functional test
- An end-to-end test proving the loop responds correctly from the simulated sensor input through the control system to the final control element.
- Alarm setpoint verification
- Driving the input with a calibrated source to the alarm value and recording the exact value at which the operator station annunciates.
- Dry commissioning
- Testing with utilities only - power, instrument air and the control system - with no process fluid present in the lines.
- Deviation record
- A documented difference between design and as-installed condition that requires engineering approval and a closed action before sign-off.
- Loop check
- Verification that wiring, tagging and signal paths are correct from the field device through the I/O card to the control system and back.
- Valve stroke test
- Driving the controller output from 0 to 100% and confirming the valve or positioner travels fully with correct position feedback.
- Fail-safe action
- The designed final-element position on signal or power loss, such as fail closed for a fuel gas shutoff valve, verified during loop checks.
- Maximum loop resistance
- Approximately supply voltage minus 12 V, divided by 0.02 A, for a 4–20 mA transmitter that needs 12 V to operate.
- Shield grounding
- Grounding the cable shield at one point only, normally the control-system end, to prevent ground loops and induced electrical noise.