Technical Trade SchoolBAS-300 service-series
BAS-305
Concept reading and source route

BAS-305 Reading Guide

How to use this reading guide

This is the concept-review layer for a 100% online course. Read each module before its lesson, complete the retrieval prompts without looking, then use the linked authoritative sources to verify project-specific editions, requirements, and manufacturer procedures.

Online evidence is not OJL: browser simulations, document cases, and isolated remote equipment build reasoning and documentation skill; supervised field performance is recorded separately.

Module 1

Measurement contract and measurand

Why it matters: A number cannot be calibrated in the abstract; define measurand, location, state, reference, tolerance, and time.

Vocabulary and working scope

What is measured; location; time; process state; expected range; acceptance source; reference; stabilization; impact; authorization; restoration.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A space sensor is compared to a handheld reference immediately after entering the room.

Calculation: Calculate expected range and stabilization window from supplied process limits and response-time data.

Retrieval prompts

Module 2

Accuracy, precision, uncertainty, and reference selection

Why it matters: High display resolution does not guarantee accuracy, and a reference must be better enough for the stated acceptance decision.

Vocabulary and working scope

Accuracy; precision; resolution; repeatability; reproducibility; hysteresis; drift; traceability; uncertainty; tolerance; certificate/status; range.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A ±0.5°F sensor is checked with a ±1.0°F reference that is near the end of its range.

Calculation: Combine supplied device and reference uncertainty using the stated course method and compare to acceptance tolerance.

Retrieval prompts

Module 3

Raw signal, scaling, units, and database path

Why it matters: Correct raw signal with wrong engineering units points toward configuration, scaling, or representation before sensor replacement.

Vocabulary and working scope

Element; transmitter; voltage/current/resistance; wire; controller raw; range; linearization; units; object; graphic; trend.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A 12 mA signal on a 4–20 mA, 0–2000 ppm input displays 2000 ppm.

Calculation: Use fraction = (signal−low signal)/(high−low), then EU = low EU + fraction×span.

Retrieval prompts

Module 4

Temperature and humidity verification

Why it matters: Agreement at one point does not prove span, response, placement, or performance across the operating range.

Vocabulary and working scope

Space/duct/outdoor/pipe sensors; immersion; insertion; stratification; radiation; airflow; wall effects; RH; dew point; time constant; simultaneous readings.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A wall sensor reads warm only when afternoon sun strikes the wall cavity behind it.

Calculation: Calculate error, percent span when authorized, dew point, response lag, and two-point offset/span pattern.

Retrieval prompts

Module 5

Pressure, differential pressure, and airflow

Why it matters: Damper position or pressure alone does not equal airflow; tubing, pickup, range, density, and K-factor must match.

Vocabulary and working scope

Static versus differential pressure; high/low ports; tubing; leaks; orientation; range; zero; pickup geometry; K-factor; density; flow station.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A VAV airflow value remains high with the fan off and one pickup tube is reversed.

Calculation: Use the supplied relationship such as flow = K×√ΔP only when K, units, density basis, and pickup geometry are defined.

Retrieval prompts

Module 6

Pneumatic signals and electro-pneumatic interfaces

Why it matters: A 3–15 psi branch signal is an analog control signal, not proof that the actuator reached position or the process responded.

Vocabulary and working scope

Main pressure; branch pressure; 3–15 psi; direct/reverse action; restriction/nozzle concepts; receiver-controller; pneumatic relay; EP/PE transducer; actuator; leaks.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A 3–15 psi actuator remains closed at 9 psi while the EP transducer output matches command.

Calculation: For a linear 3–15 psi signal, percent = (psi−3)/12×100; compare command, branch pressure, stroke, and process separately.

Retrieval prompts

Module 7

CO2, current, proof, and combined devices

Why it matters: Current proof does not prove airflow, and CO2 does not measure total IAQ or certify ventilation by itself.

Vocabulary and working scope

CO2 range and placement; current switch threshold; status/proof limitations; combined temperature/RH/CO2; cross-sensitivity; warm-up; calibration mode.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A fan current switch proves on while the belt is broken and the CO2 sensor reports a plausible but stale value.

Calculation: Calculate current threshold margin, data age, sensor error, and supplied indoor-outdoor CO2 differential without health claims.

Retrieval prompts

Module 8

Error patterns and fault isolation

Why it matters: A front-end offset can hide one displayed error while leaving failed span, location, tubing, or process causes unresolved.

Vocabulary and working scope

Offset; span; nonlinear; hysteresis; noise; intermittent; saturation; wrong range; wrong units; response lag; installation error; real process.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A sensor agrees at 70°F but is 4°F high at 90°F and 3°F low at 50°F.

Calculation: Calculate errors at each point, best-fit offset/span indication, hysteresis, noise range, and drift rate.

Retrieval prompts

Module 9

Correction decision and downstream impact

Why it matters: Correct the cause within authority; do not use software to make one display agree while corrupting alarms, resets, or analytics.

Vocabulary and working scope

Leave/monitor; device adjustment; software correction; range/configuration; repair; relocate; replace; sequence/alarm/trend impact; rollback; authority.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

A discharge-air sensor bias affects economizer logic, low-limit alarm, reset, trend, and energy analytics.

Calculation: Quantify before/after error and enumerate affected control, alarm, trend, graphic, calculation, and analytics consumers.

Retrieval prompts

Module 10

Program, as-found/as-left record, and capstone

Why it matters: Calibration interval comes from source requirements, criticality, environment, history, and risk—not a universal annual rule.

Vocabulary and working scope

Criticality; interval source; drift history; out-of-tolerance response; affected-data review; labels; certificates; work order; retest; recurrence.

Source-to-result trace

  1. Locate the controlling requirement and establish authority.
  2. Identify the physical and digital boundaries.
  3. Preserve as-found state and timestamps.
  4. Trace the initiating condition through logic, interfaces, equipment, and process response.
  5. Compare expected and actual evidence.
  6. Calculate with units and stated tolerance.
  7. Record action, result, restoration, uncertainty, and owner.

Worked thinking prompt

Three years of comparable records show increasing drift on a critical mixed-air sensor.

Calculation: Calculate drift per comparable interval and separate observed history from unsupported extrapolation.

Retrieval prompts

Required and deeper reading

Adoption note: Standards, codes, project requirements, owner criteria, manufacturer instructions, and employer safety programs control. Confirm the adopted edition and authority before applying a numeric requirement.