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PIS-CS-012/Measurement

The right instrument. The wrong range.

The wrong range can make a good instrument produce bad engineering.

Smart buildingCommercial3 min read
Select the range before trusting the numberEngineered approach for PIS-CS-012. Estimate the expected resistance and select a suitable range. Check instrument status and adjacent ranges where readings are suspect. Accept stable, repeatable results rather than one displayed number. Conceptual teaching detail, not an as-built drawing or construction instruction. © PIS Engineering Academy · All rights reserved.PIS ENGINEERING / CASE 012Select the range before trusting the numberENGINEERED APPROACHSTABLEEARTH TESTEREPCMEASUREMENT RANGELOW RANGEEXPECTED BANDHIGH RANGEOVER / UNDER-RANGEChoose from expected duty and instrument instructions; no universal range.1231Estimate the expectedresistance and select asuitable range.2Check instrument status andadjacent ranges wherereadings are suspect.3Accept stable, repeatableresults rather than onedisplayed number.READ THE DETAILEquipment, joints and current-path interfaces are shown in context.Conceptual teaching plate · no project dimensions or acceptance limits impliedPIS / REV 03© PIS Engineering Academy · All rights reserved

Engineering concept / vector field note

01

The field problem

Smart Building — Range Selection

Soil-resistivity and final-system readings were inconsistent.

why the obvious answer can be misleading

The technician selected a manual measurement range that was inappropriate for the expected resistance, reducing measurement quality and stability.

02

Why it failed

The technician selected a manual measurement range that was inappropriate for the expected resistance, reducing measurement quality and stability.

03

Follow the engineering

Switch between the field condition and the engineering concept. Trace the path and examine what changes.

Inspect the engineering detail

Select the range before trusting the numberEngineered approach for PIS-CS-012. Estimate the expected resistance and select a suitable range. Check instrument status and adjacent ranges where readings are suspect. Accept stable, repeatable results rather than one displayed number. Conceptual teaching detail, not an as-built drawing or construction instruction. © PIS Engineering Academy · All rights reserved.PIS ENGINEERING / CASE 012Select the range before trusting the numberENGINEERED APPROACHSTABLEEARTH TESTEREPCMEASUREMENT RANGELOW RANGEEXPECTED BANDHIGH RANGEOVER / UNDER-RANGEChoose from expected duty and instrument instructions; no universal range.1231Estimate the expectedresistance and select asuitable range.2Check instrument status andadjacent ranges wherereadings are suspect.3Accept stable, repeatableresults rather than onedisplayed number.READ THE DETAILEquipment, joints and current-path interfaces are shown in context.Conceptual teaching plate · no project dimensions or acceptance limits impliedPIS / REV 03© PIS Engineering Academy · All rights reserved

Case 012 · Engineered approach

100%
Select the range before trusting the numberEngineered approach for PIS-CS-012. Estimate the expected resistance and select a suitable range. Check instrument status and adjacent ranges where readings are suspect. Accept stable, repeatable results rather than one displayed number. Conceptual teaching detail, not an as-built drawing or construction instruction. © PIS Engineering Academy · All rights reserved.PIS ENGINEERING / CASE 012Select the range before trusting the numberENGINEERED APPROACHSTABLEEARTH TESTEREPCMEASUREMENT RANGELOW RANGEEXPECTED BANDHIGH RANGEOVER / UNDER-RANGEChoose from expected duty and instrument instructions; no universal range.1231Estimate the expectedresistance and select asuitable range.2Check instrument status andadjacent ranges wherereadings are suspect.3Accept stable, repeatableresults rather than onedisplayed number.READ THE DETAILEquipment, joints and current-path interfaces are shown in context.Conceptual teaching plate · no project dimensions or acceptance limits impliedPIS / REV 03© PIS Engineering Academy · All rights reserved

Scroll to inspect. Numbered details match the notes below the drawing. Conceptual geometry; use the case text for the engineering requirements.

What changes

Estimate the expected range, select the appropriate instrument scale/setup, verify over-range/under-range indications and repeat on a neighbouring range when results are suspicious.

Teaching schematic · not to scale© PIS Engineering Academy · All rights reserved
04

Correction & verification

Estimate the expected range, select the appropriate instrument scale/setup, verify over-range/under-range indications and repeat on a neighbouring range when results are suspicious.

Verification recorded in the case

  • Stable repeated values and correct instrument status are required before accepting the result.
  • Record as-built topology and connection points.
  • Repeat the measurement or functional test under a defined condition.
  • Confirm continuity and mechanical integrity of the corrected path.
  • Document instrument/setup, environmental condition and test method.
  • Close the NCR/case only when evidence supports the conclusion.
References & project context

References are reproduced from the PIS casebook. Select the governing edition and project acceptance criteria before using them for a design. The diagrams explain the concept, rather than define construction dimensions.

Instrument manufacturer instructions; IEC 61557 principles.

PIS reviewed field handbook · PIS-CS-012

View the original social card
05

The engineering lesson

Instrument setup is part of the measurement method.

Take the lesson into your next design review.

Keep exploring

Connected lessons.

All cases
Survey zone, installed soil and electrode interactionEngineered approach for PIS-CS-001. Characterise the actual soil around the installed electrodes. Coordinate spacing using the site soil model and electrode geometry. Validate probe geometry and repeatability before accepting the reading. Conceptual teaching detail, not an as-built drawing or construction instruction. © PIS Engineering Academy · All rights reserved.PIS ENGINEERING / CASE 001Survey zone, installed soil and electrode interactionENGINEERED APPROACHSURVEYED SOILBACKFILLED INSTALLATIONSOIL SURVEYSOIL RESISTIVITYC1P1P2C2COORDINATED SPACINGSoil changes across the site. Rods interact below ground.1231Characterise the actual soilaround the installedelectrodes.2Coordinate spacing using thesite soil model and electrodegeometry.3Validate probe geometry andrepeatability beforeaccepting the reading.READ THE DETAILEquipment, joints and current-path interfaces are shown in context.Conceptual teaching plate · no project dimensions or acceptance limits impliedPIS / REV 03© PIS Engineering Academy · All rights reserved
01

Measurement

Soil resistivity & rod spacing

Never Trust One Soil Resistivity Test.

New Cairo3 min
Fall-of-Potential test geometryEngineered approach for PIS-CS-004. Extend the line outside the relevant influence zone. Move the potential probe around the justified test position. Look for a defensible stable region; extend or change method if absent. Conceptual teaching detail, not an as-built drawing or construction instruction. © PIS Engineering Academy · All rights reserved.PIS ENGINEERING / CASE 004Fall-of-Potential test geometryENGINEERED APPROACHVERIFYEARTH TESTEREPCPCEXTEND BEYOND INFLUENCEConfirm the curve around the justified potential-probe position.SCHEMATIC TEST CURVE1231Extend the line outside therelevant influence zone.2Move the potential probearound the justified testposition.3Look for a defensible stableregion; extend or changemethod if absent.READ THE DETAILEquipment, joints and current-path interfaces are shown in context.Conceptual teaching plate · no project dimensions or acceptance limits impliedPIS / REV 03© PIS Engineering Academy · All rights reserved
04

Measurement

The grid was blamed. The test was wrong.

The earth grid was blamed. The test geometry was wrong.

Upper Egypt3 min
A rock mass interrupts the test circuitEngineered approach for PIS-CS-005. Change test direction and place auxiliary probes in suitable ground. Increase separation as required to establish the injection circuit. Confirm injection and repeatability before interpreting resistance. Conceptual teaching detail, not an as-built drawing or construction instruction. © PIS Engineering Academy · All rights reserved.PIS ENGINEERING / CASE 005A rock mass interrupts the test circuitENGINEERED APPROACHVERIFYEARTH TESTEREPCPCBURIED ROCK MASSChange the test direction to establish an injection circuit.1231Change test direction andplace auxiliary probes insuitable ground.2Increase separation asrequired to establish theinjection circuit.3Confirm injection andrepeatability beforeinterpreting resistance.READ THE DETAILEquipment, joints and current-path interfaces are shown in context.Conceptual teaching plate · no project dimensions or acceptance limits impliedPIS / REV 03© PIS Engineering Academy · All rights reserved
05

Measurement

An open loop in rocky ground

OPEN LOOP did not mean an open earthing system.

New Minya3 min
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