Data acquisition faults — cause × symptom matrix and 4 isolation flowcharts (DAS)

Hazard: Touching a Converter-16 or Control-16 PWB with bare hands while carrying out the repeated 'exchange the PWB with the adjacent/another-slot PWB' steps in these flowcharts (§2.8.1)

Consequence: invisible ESD damage to the board

Avoidance: wear clean cotton gloves whenever a PWB is handled; if a PWB is handled bare-handed, clean it with ethanol

Hazard: Touching the DAS PWB parts or pattern surface with hands or objects while running these checks

Consequence: oil/water contamination degrades signal quality ("SD", as termed in source) — directly relevant to the Large image SD / SD trouble symptom this page diagnoses

Avoidance: avoid touching the DAS PWB parts or pattern surface

Hazard: Selecting the wrong DAS gain when running a DCA acquisition in any of these flowcharts — ordinary image acquisition auto-selects gain, but DCA acquisition requires manual gain selection

Consequence: the DCA output count can read extremely small or overflow, producing a false result on any 'check the X-ray output by DCA' / offset-acquisition step below

Avoidance: for DCA acquisition, manually select the DAS gain appropriate to slice thickness, FOV, and kV before reading the result

Hazard: Main detector temperature outside its stable band while running the Ring-image flowchart's first check

Consequence: image artifacts (ring image)

Avoidance: keep the main detector at the required temperature — this is exactly what the temperature-controller display (36°C to 38°C normal) checked in step 1 of the Ring image flowchart verifies