Conductivity and salinity measurement: 50 selection, application and maintenance questions

Conductivity reflects the combined ionic transport of a solution and depends on composition and temperature. Salinity and TDS are model-derived, not independent measurements of every ion or universally fixed mass conversions. The principle explains signal generation; it does not establish the range, accuracy, materials or approvals of every model. Review the physical principle and the application limits separately.

Verification: Confirm "Conductivity, resistivity, salinity or TDS objective" and assess "Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished." against the actual application. Record the complete model and document revision used.

适用边界：Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished.

Define the quantity to be accepted before selecting a display unit. Conductivity reflects the combined ionic transport of a solution and depends on composition and temperature. Salinity and TDS are model-derived, not independent measurements of every ion or universally fixed mass conversions. For "Conductivity, resistivity, salinity or TDS objective", document output definitions and conversion or compensation conditions; displaying a value does not make it a direct measurement under all conditions.

Verification: Document the process objective, units and reference conditions. Check "Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished." and list separate inputs and acceptance methods for calculated results.

适用边界：Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished.

Prepare at least these five input groups: Conductivity, resistivity, salinity or TDS objective; Range and cell-constant requirements; Ionic composition and contaminants; Temperature location and compensation model; Contacting or inductive sensor construction. Mark unknown items for confirmation instead of substituting a normal point or an assumed default for all conditions.

Verification: Have process, instrumentation and purchasing roles agree the inputs, particularly "Range and cell-constant requirements". Resolve missing evidence before requesting application confirmation.

适用边界：Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished.

Select the range from actual operating conditions and permissible error, then check extremes and installation constraints. For this family: Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished. Nominal size or maximum equipment rating need not equal the useful measuring interval.

Verification: List minimum, normal, maximum and abnormal conditions. Check "Ionic composition and contaminants" against the documented performance envelope.

适用边界：Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished.

No. Low-end usability depends on the principle, available signal and error mechanisms. A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass. More display digits, software scaling or a stated turndown cannot remove the original noise or installation error.

Verification: Obtain error definitions and limits at the actual low operating point. Use "Flow-dependent readings: inspect bubbles, wetting and clearances for changed field or sample conditions." to investigate bias instead of comparing only percent-of-full-scale values.

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

Use the complete measured object and actual exposure, rather than a material name alone. Temperature location and compensation model Avoid this family-specific misuse: A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass. For non-wetted equipment, assess loads, target materials, signals and environmental compatibility instead.

Verification: List the actual contact or loading parts, seals, insulation and cleaning conditions. Have the responsible parties assess "Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes.".

适用边界：Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes.

Normal measurement, temporary excursions and survival limits are different requirements. Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes. Start-up, cleaning, impacts, power interruption or abnormal environments can determine the necessary construction and protection.

Verification: Complete the worst-case conditions using "Contacting or inductive sensor construction" and check "Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.". Separate continuous operating limits from temporary limits in the specification.

适用边界：Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.

Not without assessment. Use traceable conductivity references spanning the operating region and with defined temperature conditions. Verify cell constant and temperature separately; validate salinity/TDS conversions independently for the sample matrix. The installed system also includes object, mounting, signal conversion, environmental and reference effects. Derived results additionally depend on the relevant input uncertainties.

Verification: Agree actual test points, installation conditions and the acceptance reference. Check "Make the measurement or sample representative; record conditioning and transport delay without unvalidated removal of the target constituent" and document the system error or uncertainty basis.

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

A stable indication and fast change detection involve a trade-off; filtering cannot repair incorrect installation or real process variation. Ultrapure-water increase after opening: atmospheric CO2 and container contamination can invalidate a direct open-cup comparison. Review the complete chain when fast response matters, not merely the display refresh rate.

Verification: Define the shortest relevant event and acceptable delay. Check "Use clean compatible sampling equipment and wetted materials to avoid contamination or adsorption" and verify local output, display and receiving-system response using a controlled change.

适用边界：Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes.

Typical contexts include: Inline versus laboratory comparisons require the same location, time, reporting units and method, retaining raw values and conditioning records; Process-control use requires validation of delay, quality status and control behaviour on failure; For reporting, establish the required method and applicable documentation; a correlation or trend is not automatically an accepted analytical result. Similar application labels do not establish equivalent conditions. In particular, assess "Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models." before relying on another installation as proof.

Verification: Select the nearest application and compare "Conductivity, resistivity, salinity or TDS objective" and "Contacting or inductive sensor construction". Obtain written confirmation where published application limits are exceeded.

适用边界：Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.

Translate required functions, performance and physical interfaces into verifiable options. Match the measurand and reporting basis: Conductivity and conditionally derived salinity or TDS; Compare the actual sensing method and compensation model: Conductivity reflects the combined ionic transport of a solution and depends on composition and temperature. Salinity and TDS are model-derived, not independent measurements of every ion or universally fixed mass conversions.. Options affecting suitability or supply scope should be explicit; terms such as standard or same as existing are insufficient.

Verification: Check the complete order code and selection sheet, especially "Ionic composition and contaminants". List accessories, documents, calibration and delivery boundaries separately.

适用边界：Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished.

Make the measurement or sample representative; record conditioning and transport delay without unvalidated removal of the target constituent The installation drawing must match the available space and process or mechanical structure. Access for fitting and servicing should be established before delivery.

Verification: Review a dimensioned, oriented site drawing. Use "Temperature location and compensation model" and "Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes." to confirm connections, support, removal access and safe isolation.

适用边界：Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes.

Verify sensing-zone temperature, pressure, flow and stability for the selected analytical method Supporting conditions are part of the measurement system. Matching mechanical connections or signal names alone do not establish power, I/O, grounding or configuration compatibility.

Verification: Confirm "Match the sampling or installation conditions: Make the measurement or sample representative; record conditioning and transport delay without unvalidated removal of the target constituent" and "Use the same independent reference procedure: Use traceable conductivity references spanning the operating region and with defined temperature conditions. Verify cell constant and temperature separately; validate salinity/TDS conversions independently for the sample matrix." against actual terminals, loops and receiving-system settings.

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

Check identity, installation and basic conditions first, then status, output and process response. Use clean compatible sampling equipment and wetted materials to avoid contamination or adsorption Preserve original evidence for unexplained anomalies instead of concealing them with zero or factor adjustments.

Verification: Record factory settings and initial status. Investigate "Good standard but biased sample: examine compensation, bubbles and composition before altering the cell constant to fix a TDS model." step by step and change parameters only after identifying the cause and using an authorised procedure.

适用边界：Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes.

No. Establish the represented object and reference conditions: Match the measurand and reporting basis: Conductivity and conditionally derived salinity or TDS. Electrical equipment also needs loop type, scaling, failure behaviour and protocol details checked. Mechanical indicators require clear boundaries between indication and remote-transmission accessories.

Verification: Check the receiving-system variable against "Conductivity, resistivity, salinity or TDS objective" and verify limits, units and abnormal states with the actual equipment. Record wiring, configuration and end-to-end checks against "Verify sensing-zone temperature, pressure, flow and stability for the selected analytical method".

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

Use traceable conductivity references spanning the operating region and with defined temperature conditions. Verify cell constant and temperature separately; validate salinity/TDS conversions independently for the sample matrix. The report should identify the delivered instrument, measured quantity, conditions, method and results. A general conformity certificate does not establish performance for every option or operating condition.

Verification: Check serial number, points, units, reference equipment and traceability. Compare "Range and cell-constant requirements" with the calibrated conditions and agree separate acceptance where they differ.

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

Identify alarm/control duties and follow authorised electrical isolation, chemical and waste-handling procedures Agree criteria before testing, including range, conditions, error definition and treatment of anomalies. Similar-looking readings or an unsuitable portable reference are not sufficient acceptance evidence.

Verification: Choose an appropriate reference using "Use traceable conductivity references spanning the operating region and with defined temperature conditions. Verify cell constant and temperature separately; validate salinity/TDS conversions independently for the sample matrix.". Record "Conductivity, resistivity, salinity or TDS objective" and test conditions; investigate "Flow-dependent readings: inspect bubbles, wetting and clearances for changed field or sample conditions." before deciding on rework or recalibration.

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

Define why the standard supply is insufficient, the required verification and the responsible parties. Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.; Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.. Additional materials, construction, documents or tests depend on actual requirements.

Verification: Attach "Contacting or inductive sensor construction" and the deviations. Obtain technical confirmation, additional charges, delivery conditions and acceptance methods; unknown requirements must not be assumed satisfied.

适用边界：Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.

Good standard but biased sample: examine compensation, bubbles and composition before altering the cell constant to fix a TDS model. Distinguish the actual measured condition from device-state and readout or transmission faults. Do not immediately interpret missing data as sensor failure or a zero process value.

Verification: Under appropriate safe isolation, check "Verify sensing-zone temperature, pressure, flow and stability for the selected analytical method". Compare local and receiving-end status and record when the fault appeared.

适用边界：Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished.

Ultrapure-water increase after opening: atmospheric CO2 and container contamination can invalidate a direct open-cup comparison. Compare independent process evidence and raw signals before deciding whether installation, interference or equipment is responsible. More filtering can hide a real abnormal event.

Verification: Keep conditions comparable and record correlation with process or equipment events. Check "Make the measurement or sample representative; record conditioning and transport delay without unvalidated removal of the target constituent" and change one factor at a time.

适用边界：Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes.

Flow-dependent readings: inspect bubbles, wetting and clearances for changed field or sample conditions. Systematic bias can arise from units, reference conditions, configuration, installation or the reference method. An unexplained correction can move one operating-point error to other conditions.

Verification: Align quantities, time bases and units first. Review the reference using "Use traceable conductivity references spanning the operating region and with defined temperature conditions. Verify cell constant and temperature separately; validate salinity/TDS conversions independently for the sample matrix." and confirm that "Range and cell-constant requirements" matches the configuration.

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

Persistent bias: investigate deposits, corrosion, configuration and temperature sensing before reference comparison. Establish a genuine, stable reference condition that meets the method requirements before considering adjustment. Some instruments have no freely adjustable site zero.

Verification: Check "Use clean compatible sampling equipment and wetted materials to avoid contamination or adsorption" and "Use traceable conductivity references spanning the operating region and with defined temperature conditions. Verify cell constant and temperature separately; validate salinity/TDS conversions independently for the sample matrix." and retain before-and-after results. If the conditions cannot be established, remove external effects or use a qualified service.

适用边界：Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes.

Large replacement error: verify cell constant, two/four-electrode or inductive compatibility and units instead of applying an offset. Intermittent faults need correlated event records, not just a normal display after recovery. Review alarm settings, communication status and actual process abnormalities separately.

Verification: Retain time, status codes, raw trends and the contemporaneous "Contacting or inductive sensor construction". Compare "Verify sensing-zone temperature, pressure, flow and stability for the selected analytical method" and "Use clean compatible sampling equipment and wetted materials to avoid contamination or adsorption" to locate the failing link.

适用边界：Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.

Repeated failures warrant a common-cause assessment. Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models. If the external conditions remain unchanged, an identical construction or installation can experience the same failure again.

Verification: Summarise failed parts, service time and "Contacting or inductive sensor construction". Check "Make the measurement or sample representative; record conditioning and transport delay without unvalidated removal of the target constituent" and "Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes." and establish corrective action before selecting repair or redesign.

适用边界：Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes.

Use traceable conductivity references spanning the operating region and with defined temperature conditions. Verify cell constant and temperature separately; validate salinity/TDS conversions independently for the sample matrix. A comparison identifies differences; adjustment changes indication or parameters; calibration establishes a reference relationship under stated conditions. They are not interchangeable claims.

Verification: Define what performance and evidence must be established, using conditions relevant to "Range and cell-constant requirements". Retain original and adjusted results, references and responsibility records.

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

The same basic model does not establish identical options, software, calibration or accessories. Use the same independent reference procedure: Use traceable conductivity references spanning the operating region and with defined temperature conditions. Verify cell constant and temperature separately; validate salinity/TDS conversions independently for the sample matrix.; Verify the full order code, wiring/protocol, alarm role, wetted materials, documentation and site acceptance; a common principle does not prove interchangeability.. Previous system operation does not remove the need to verify a replacement.

Verification: Compare full order codes and revisions. Recheck critical points, failure states and interfaces using "Identify alarm/control duties and follow authorised electrical isolation, chemical and waste-handling procedures" before handover.

适用边界：Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.

No. Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished. Maximum values usually relate to particular options and conditions. Temperature, load, pressure, materials, speed or signal conditions may constrain one another.

Verification: Review "Ionic composition and contaminants" and "Contacting or inductive sensor construction" together. Obtain confirmation for the combined conditions instead of assembling unrelated maxima from separate pages.

适用边界：Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished.

No. Good standard but biased sample: examine compensation, bubbles and composition before altering the cell constant to fix a TDS model. Indication, measurement and transmission have distinct possible failure modes. Also consider "Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished."; establish the actual process condition independently.

Verification: Check available status or failure indications and "Match the sampling or installation conditions: Make the measurement or sample representative; record conditioning and transport delay without unvalidated removal of the target constituent". For interlocks, follow the complete safety design rather than substituting a zero value for diagnosis.

适用边界：Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished.

No. Use traceable conductivity references spanning the operating region and with defined temperature conditions. Verify cell constant and temperature separately; validate salinity/TDS conversions independently for the sample matrix. Test points and directions must reflect the working interval, relevant error mechanisms and acceptance purpose. Multiple points, reversal or load tests depend on the method.

Verification: Define acceptance coverage against "Range and cell-constant requirements" and include critical operating points. Mark conditions outside the tests as unverified.

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

Not necessarily. Options should serve the required objective; excess configuration can add cost, complexity or incompatibility. A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.; A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.. Establish essential requirements before comparing optional benefits.

Verification: Document the objective in "Conductivity, resistivity, salinity or TDS objective" and why "Match the measurand and reporting basis: Conductivity and conditionally derived salinity or TDS" is needed. Compare performance at actual working points rather than one headline metric.

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

Not independently of risk and history. Use traceable conductivity references spanning the operating region and with defined temperature conditions. Verify cell constant and temperature separately; validate salinity/TDS conversions independently for the sample matrix. Intervals depend on applicable law or contract, conditions, drift, maintenance and failure evidence. Generic advice cannot replace mandatory requirements.

Verification: Use "Persistent bias: investigate deposits, corrosion, configuration and temperature sensing before reference comparison." and "Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models." to establish and review an initial plan. Retain the justification and approval for interval changes.

适用边界：Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.

Physical fit is insufficient. Compare the actual sensing method and compensation model: Conductivity reflects the combined ionic transport of a solution and depends on composition and temperature. Salinity and TDS are model-derived, not independent measurements of every ion or universally fixed mass conversions.; Match the sampling or installation conditions: Make the measurement or sample representative; record conditioning and transport delay without unvalidated removal of the target constituent. Matching, materials, signals, calibration and approval boundaries can change with the combination.

Verification: Check the complete combination against "Verify sensing-zone temperature, pressure, flow and stability for the selected analytical method" and obtain compatibility and acceptance evidence. An unconfirmed assembly must not be described as an approved system.

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

Check the exact order configuration and valid documents rather than a series name. Verify the full order code, wiring/protocol, alarm role, wetted materials, documentation and site acceptance; a common principle does not prove interchangeability. "Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models." also matters; certificates, installation conditions and restrictions together define suitability.

Verification: Obtain certificate identifiers, covered models and special conditions and match them to the site. Similar names do not grant functional-safety or legal-metrology approval.

适用边界：Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.

Establish the chain from quantity definition and application limits through configuration, mounting, reference and operating status. Identify alarm/control duties and follow authorised electrical isolation, chemical and waste-handling procedures A normal indication or brochure alone cannot demonstrate continuing system reliability.

Verification: Put "Conductivity, resistivity, salinity or TDS objective", "Use traceable conductivity references spanning the operating region and with defined temperature conditions. Verify cell constant and temperature separately; validate salinity/TDS conversions independently for the sample matrix." and "Large replacement error: verify cell constant, two/four-electrode or inductive compatibility and units instead of applying an offset." into the technical, acceptance and maintenance records, with responsibility for reviewing excursions.

适用边界：Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.

Possibly, after a full configuration and application comparison. A basic model name or matching output is not proof of equivalent replacement. Match the measurand and reporting basis: Conductivity and conditionally derived salinity or TDS; Compare the actual sensing method and compensation model: Conductivity reflects the combined ionic transport of a solution and depends on composition and temperature. Salinity and TDS are model-derived, not independent measurements of every ion or universally fixed mass conversions.; Match the sampling or installation conditions: Make the measurement or sample representative; record conditioning and transport delay without unvalidated removal of the target constituent. Record conclusions on material differences.

Verification: Provide the original full order code, data sheet and site conditions. Check "Use the same independent reference procedure: Use traceable conductivity references spanning the operating region and with defined temperature conditions. Verify cell constant and temperature separately; validate salinity/TDS conversions independently for the sample matrix." and "Verify the full order code, wiring/protocol, alarm role, wetted materials, documentation and site acceptance; a common principle does not prove interchangeability." and obtain the necessary test and approval evidence before replacement.

适用边界：Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.

Base the decision on project compliance and documented delivery or service, rather than a slogan. "Conductivity, resistivity, salinity or TDS objective" and "Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished." are important family-specific checks. Claim only benefits supported by the offered product documents and written commitments.

Verification: Request the proposed configuration matching "Match the measurand and reporting basis: Conductivity and conditionally derived salinity or TDS", test evidence and delivery/service terms. Do not infer unverified performance, approvals, origin or service life.

适用边界：Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished.

Use identical conditions and supply boundaries. Match the measurand and reporting basis: Conductivity and conditionally derived salinity or TDS; Match the sampling or installation conditions: Make the measurement or sample representative; record conditioning and transport delay without unvalidated removal of the target constituent; Verify the full order code, wiring/protocol, alarm role, wetted materials, documentation and site acceptance; a common principle does not prove interchangeability.. Quotes with different ranges, compensation, accessories or calibration scope can conceal material differences.

Verification: Compare "Range and cell-constant requirements", "A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass." and mounting/acceptance conditions. Separate demonstrated, unverified and inapplicable items; do not claim unproven overall superiority.

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

Compare complete supply and use-cycle costs, not only the main instrument price. Make the measurement or sample representative; record conditioning and transport delay without unvalidated removal of the target constituent; Use traceable conductivity references spanning the operating region and with defined temperature conditions. Verify cell constant and temperature separately; validate salinity/TDS conversions independently for the sample matrix. List the actual installation, supporting equipment, calibration, consumables, downtime and service requirements without assuming any brand is always cheaper.

Verification: Use the same "Match the measurand and reporting basis: Conductivity and conditionally derived salinity or TDS" configuration and "Contacting or inductive sensor construction" boundary. Separate equipment, accessories, commissioning and maintenance responsibilities and retain a traceable comparison.

适用边界：Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.

Conductivity reflects the combined ionic transport of a solution and depends on composition and temperature. Salinity and TDS are model-derived, not independent measurements of every ion or universally fixed mass conversions.

Verification: Make the measurement or sample representative; record conditioning and transport delay without unvalidated removal of the target constituent. Check Conductivity, resistivity, salinity or TDS objective. Retain raw and reference values, timestamps and compensation settings; repeat the comparison before changing the instrument.

适用边界：Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished.

Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished.

Verification: Verify sensing-zone temperature, pressure, flow and stability for the selected analytical method. Check Range and cell-constant requirements. Retain raw and reference values, timestamps and compensation settings; repeat the comparison before changing the instrument.

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

Verification: Use clean compatible sampling equipment and wetted materials to avoid contamination or adsorption. Check Ionic composition and contaminants. Retain raw and reference values, timestamps and compensation settings; repeat the comparison before changing the instrument.

适用边界：Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes.

Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes.

Verification: Identify alarm/control duties and follow authorised electrical isolation, chemical and waste-handling procedures. Check Temperature location and compensation model. Retain raw and reference values, timestamps and compensation settings; repeat the comparison before changing the instrument.

适用边界：Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.

Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.

Verification: Make the measurement or sample representative; record conditioning and transport delay without unvalidated removal of the target constituent. Check Contacting or inductive sensor construction. Retain raw and reference values, timestamps and compensation settings; repeat the comparison before changing the instrument.

适用边界：Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished.

Good standard but biased sample: examine compensation, bubbles and composition before altering the cell constant to fix a TDS model.

Verification: Verify sensing-zone temperature, pressure, flow and stability for the selected analytical method. Check Conductivity, resistivity, salinity or TDS objective. Retain raw and reference values, timestamps and compensation settings; repeat the comparison before changing the instrument.

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

Ultrapure-water increase after opening: atmospheric CO2 and container contamination can invalidate a direct open-cup comparison.

Verification: Use clean compatible sampling equipment and wetted materials to avoid contamination or adsorption. Check Range and cell-constant requirements. Retain raw and reference values, timestamps and compensation settings; repeat the comparison before changing the instrument.

适用边界：Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes.

Flow-dependent readings: inspect bubbles, wetting and clearances for changed field or sample conditions.

Verification: Identify alarm/control duties and follow authorised electrical isolation, chemical and waste-handling procedures. Check Ionic composition and contaminants. Retain raw and reference values, timestamps and compensation settings; repeat the comparison before changing the instrument.

适用边界：Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.

Persistent bias: investigate deposits, corrosion, configuration and temperature sensing before reference comparison.

Verification: Make the measurement or sample representative; record conditioning and transport delay without unvalidated removal of the target constituent. Check Temperature location and compensation model. Retain raw and reference values, timestamps and compensation settings; repeat the comparison before changing the instrument.

适用边界：Resistivity and conductivity are reciprocal with consistent units; trace contamination matters in ultrapure water and raw/compensated values must be distinguished.

Large replacement error: verify cell constant, two/four-electrode or inductive compatibility and units instead of applying an offset.

Verification: Verify sensing-zone temperature, pressure, flow and stability for the selected analytical method. Check Contacting or inductive sensor construction. Retain raw and reference values, timestamps and compensation settings; repeat the comparison before changing the instrument.

适用边界：A TDS factor depends on ionic composition; equal conductivity does not establish equal dissolved-solids mass.

Use traceable conductivity references spanning the operating region and with defined temperature conditions. Verify cell constant and temperature separately; validate salinity/TDS conversions independently for the sample matrix.

Verification: Use clean compatible sampling equipment and wetted materials to avoid contamination or adsorption. Check Conductivity, resistivity, salinity or TDS objective. Retain raw and reference values, timestamps and compensation settings; repeat the comparison before changing the instrument.

适用边界：Cell constant, construction and range must match; different contacting and inductive sensors are not setting-free substitutes.

Inline versus laboratory comparisons require the same location, time, reporting units and method, retaining raw values and conditioning records. Make the measurement or sample representative; record conditioning and transport delay without unvalidated removal of the target constituent

Verification: Identify alarm/control duties and follow authorised electrical isolation, chemical and waste-handling procedures. Check Range and cell-constant requirements. Retain raw and reference values, timestamps and compensation settings; repeat the comparison before changing the instrument.

适用边界：Temperature dependence is not universal; pure water, salts and acids require suitable validated compensation models.