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Calibration and handover records describe how a measurement was checked, what maintenance changed and which data periods need review. Keep standards, reference results, before-service readings, adjustments and final checks linked to the installed point. These records help distinguish changes in water conditions from changes in sensor condition.
This guide focuses on measurement and maintenance evidence after startup. For PLC registers, scaling, tags and communication tests, use the sensor data handover guide. A correct data path and a valid measurement check are separate parts of acceptance.
Separate Calibration, Verification and Cleaning
| Activity | Purpose | Record |
|---|---|---|
| Calibration | Establish the response to a specified reference; adjustment may be part of the model procedure | Reference, method, conditions, observed response and any adjustment. |
| Verification | Check performance against an agreed method or reference without automatically changing settings | Measured and reference values, criterion, conditions and result. |
| Cleaning | Remove deposits or fouling using the approved service procedure | Before and after readings, cleaning method, observations and time. |
Follow the procedure for the selected model and parameter. An adjustment, a comparison with a handheld meter and a cleaning event should not all be labeled as the same activity. Keep their sequence visible so a later reviewer can understand why the reading changed.
Record the Condition Before Service
Before removing or cleaning the probe, record its reading, time, point identifier and visible condition. Add relevant water temperature, flow or process state, and a reference reading when the agreed method requires one. Note whether the point was submerged and whether sample delivery or communication was interrupted.
A reference comparison needs a meaningful match in location and timing. State the reference method and any sample handling; do not assume that a sample collected elsewhere represents the installed sensor point. Check the reference instrument or material is suitable for the task.
Keep a Clear Service Sequence
| Stage | What to capture | How it helps |
|---|---|---|
| Before cleaning | Reading, condition and matched reference where applicable | Preserves evidence of the point before intervention. |
| After cleaning | Reading after the model’s stabilization requirements are met | Shows the change associated with service. |
| Reference check or calibration | Material or method, conditions, results and adjustments | Documents whether further action was required. |
| Return to operation | Final check, service status, installed position and next action | Confirms the point was restored and identifies follow-up. |
Cleaning, reference checks and calibration should follow the model’s approved procedure. Do not create a universal stabilization time, standard concentration or maintenance interval for different sensors. Record the actual procedure and conditions used.
Minimum Fields for a Reusable Record
| Field group | Required detail |
|---|---|
| Identity | Point name, location, model, serial number and parameter. |
| Reference | Method, reference instrument or standard identity, lot and validity where applicable, and conditions. |
| Results | Values and units before service, after cleaning, during reference checks and after any adjustment. |
| Action | Cleaning, configuration or component changes; technician and timestamps. |
| Disposition | Acceptance criterion, result, unresolved issue, reviewer and next service action. |
For a multi-parameter probe, keep results identifiable by channel. A passed pH check does not establish the condition of DO, conductivity or another channel. Retain the applicable document revision with the service method and avoid copying settings from a different product variant.
Use Records When a Reading Is Questioned
Review the event timeline before adjusting the instrument. Compare process changes, cleaning times, component replacement, reference results and data-path changes. A step after maintenance has a different investigation path from a trend that follows pumping, dosing or production.
Keep the original observations and any reviewed data changes distinguishable. If a reporting workflow allows data correction, apply its documented method, approval and audit trail; do not silently replace raw readings. Identify gaps, maintenance periods and unresolved data quality concerns for the intended use.
Set Acceptance Criteria Before the Check
Agree the reference method, comparison conditions, acceptable difference and action on failure before sign-off. Use the selected sensor’s documented performance and the application’s needs. An arbitrary tolerance shared across unrelated parameters does not provide meaningful acceptance.
A commissioning check establishes a documented starting condition. It does not guarantee future performance without maintenance and periodic review. Plan follow-up from the model instructions, water conditions and observed fouling or drift, then retain the reason for changing the schedule.
Frequently Asked Questions
What is the difference between calibration and verification?
Calibration establishes the response to a specified reference; adjustment may be included in the device procedure. Verification checks performance against an agreed criterion. Record what was actually done.
Why record values before and after cleaning?
The comparison preserves evidence of the change associated with service. Add timing and process context because water conditions may also change during the intervention.
Should a sensor be recalibrated every time it is cleaned?
Follow the selected model’s procedure and the reference-check result. Cleaning and calibration serve different purposes; an adjustment should have a recorded reason.
Can a handheld result be used as a reference?
Only when the method, instrument condition, location, timing and comparison conditions are suitable for the task. Record those details rather than relying on the instrument name alone.
What should a standard record include?
Identify the material, specified value and unit, lot and validity where applicable, relevant conditions and the actual result. Use the material required by the model procedure.
How should replacement parts be documented?
Record the component, model compatibility, date and any settings or checks required after replacement. Link the final verification to the same point history.
Can one maintenance interval apply to every point?
Intervals depend on model instructions, water conditions, fouling and the required data quality. Use service history to review the schedule rather than imposing one interval across all sites.
What evidence is useful for troubleshooting?
Provide the point and model, before-and-after readings, reference method, service sequence, photos and relevant process events. Include the questioned time period and any unresolved acceptance issue.
Prepare the Handover File
Keep the installation record, applicable service instructions, first accepted results and next maintenance action together. Assign who performs service, who reviews failed checks and who decides whether a data period is suitable for its intended use. For model support, provide the parameter, water conditions and documented results so YexSensor can review the relevant procedure.
Technical Reading
USGS: Guidelines and Standard Procedures for Continuous Water-Quality Monitors discusses field procedures, sensor checks and record review. Use the applicable model instructions for the actual maintenance and calibration procedure.
