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An indicated level can move even when the liquid inventory does not. Foam changes the apparent interface, density changes float immersion, deposits add mass or friction, and coating on a resistive card can alter contact or leakage. The measurement chain must state what physical surface it follows and under which process state. A calibration made with clean water cannot automatically represent aerated product, slurry or aged process liquid. System owners must relate tank geometry, medium condition, mechanism, card and electronics through controlled observations.
System boundary
The boundary includes process vessel, medium, foam layer, float or moving element, linkage, pivot, resistive card, seals, terminals, receiver and cleaning process. ChipSimple may review drawing-defined card features. Process compatibility, vessel safety, calibration and alarm strategy remain customer-owned.
System integration decisions
- Define whether the measurand is liquid interface, bulk volume or another process quantity.
- Measure density and foam state with each calibration point.
- Separate buoyancy changes from pivot friction and electrical surface effects.
- Control cleaning and deposit condition as configuration variables.
State which physical boundary defines level
Separate bulk-liquid interface from foam top, settled solids and vessel volume. Define datum, attitude and independent reference method. If the process intentionally contains foam, specify whether it should be ignored, tracked or treated as an invalid state. Record agitation and pressure because they alter gas fraction. A display percentage without this physical definition cannot support diagnosis or calibration.
Relate density to float immersion
A floating body displaces mass equal to supported effective mass at equilibrium.
V_disp=m_eff/rho; Delta V_disp=m_eff(1/rho_2-1/rho_1)
- V_disp is displaced liquid volume.
- m_eff is float plus reflected supported mass.
- rho is liquid density at the evaluated state.
Static free float without wall contact; surface tension, foam support, acceleration and deposits require separate assessment.
Calculate an illustrative density shift
For an effective supported mass of 24 g, equilibrium displacement is 30.0 cm³ at 800 kg/m³ and 26.7 cm³ at 900 kg/m³, a change of 3.3 cm³. Translation into vertical immersion depends on float shape. These values are not application specifications. They show why a fixed electrical curve may shift when process concentration or temperature changes density.
Characterize foam as a separate phase
Record foam depth, drainage, bubble size, stability and whether it exerts buoyant support or drag. A float may sit partly in foam, oscillate at its lower boundary or become held by dried residue. Compare readings with an independent liquid-interface method selected by the process owner. Do not treat one laboratory surfactant mixture as representative of every production formulation.
Locate deposit effects on mass, clearance and friction
Map deposits on float, arm, pivot, card, seals and housing. Added float mass changes displacement; buildup near a pivot changes friction; a bridge at a stop changes travel. Preserve as-found condition before cleaning. Weighing or dimensional records can support mechanism diagnosis, while surface electrical measurements can assess card-related effects. One clean component cannot isolate a system that remains fouled elsewhere.
Measure fill and drain paths separately
Approach controlled levels from both directions after stated dwell. Record independent level, density, foam condition, mechanical coordinate and raw electrical output. A directional band can indicate friction or adhesion, whereas a consistent offset correlated with density suggests buoyancy. Rapid agitation can create a dynamic error not present at equilibrium. Keep the unfiltered channel so controller smoothing does not erase sticking events.
Use a state matrix for separation
Choose safe states that distinguish competing mechanisms.
| State | Observation | Owner |
|---|---|---|
| Clean reference fluid | Geometry and electrical baseline | Calibration owner |
| Changed density | Float immersion and output | Process owner |
| Defined foam condition | Independent interface and float behavior | Process measurement owner |
| As-found deposits | Mass, clearance, hysteresis and leakage | Maintenance and electrical owners |
| Post-cleaning | Recovery plus material inspection | Materials authority |
Distinguish surface leakage from mechanical shift
Measure card response directly where safe and compare it with installed receiver values. A mechanical coordinate change with stable card transfer points to float or linkage. An electrical change at fixed wiper position suggests contact, leakage, harness or acquisition. Inspect wet-to-dry boundaries and terminal contamination. Do not generalize compatibility from visual appearance or one resistance measurement.
Treat cleaning as a controlled material exposure
Specify chemistry, concentration, temperature, agitation, tools, dwell and rinse. Cleaning can restore motion while damaging seals or leaving conductive residue. Record before and after mass, clearance, raw output and relevant inspection. The customer materials owner approves process-fluid and cleaning compatibility. Card construction remains by drawing and application review rather than a universal chemical claim.
Validate representative process states
Use the actual vessel geometry or an evidence-based fixture, controlled attitude and traceable level reference. Include clean baseline, density bounds, defined foam, realistic deposit states and relevant agitation. Acquire process condition, mechanical position and raw signal together. The integrator owns accuracy, alarm and safe-operation criteria. ChipSimple review does not certify the complete level instrument.
Reopen calibration after process or mechanism changes
Changes to formulation, concentration, temperature, gas content, float, arm, pivot, card, seal, housing, cleaning or signal processing can invalidate prior evidence. Bind calibration to revisions and fluid state. A software offset after fouling may mask worsening friction; a new float may alter buoyancy even with identical travel. Review the physical chain before accepting compensation.
Keep process claims bounded
This page does not promise compatibility with unnamed fluids, foam rejection, deposit tolerance or a maintenance interval. Those outcomes require specified materials, exposure and validation. Provide safety and hazardous-process constraints before testing. Illustrative calculations organize decisions only. If fluid identity or independent level reference is unavailable, the cause and calibration remain unresolved.
Provide the process-fluid and indication chain
Review needs process state, mechanism geometry and raw electrical evidence.
- Fluid composition, density, temperature, foam, solids and agitation.
- Vessel geometry, datum, attitude and independent level reference.
- Float, arm, pivot, stops, clearances, card and wiper details.
- Wetting, sealing, deposits, cleaning method and maintenance state.
- Receiver circuit, filtering, calibration, alarms and validation ownership.
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