Scope
Where this method applies
Use for compatible liquid samples and for root-zone extracts only when the extraction method is defined and kept consistent.
Root-zone measurement · THC SOP
EC Meter Verification & Measurement
Generate consistent electrical-conductivity readings while preserving the sample method, temperature context, and instrument verification needed for comparison over time.
Frequency
When to run it
Verify or calibrate at the interval recommended by the meter manufacturer and after storage, cleaning, probe replacement, or suspicious readings.
Preparation
Tools and preconditions
Required tools
- EC/conductivity meter
- appropriate conductivity standard
- clean rinse water
- clean sample cup
- record sheet or digital log
Before starting
- Confirm the standard is within its usable date and has not been contaminated.
- Know whether the meter reports EC directly or converts to another scale.
- Define the sampling method before comparing root-zone readings.
Procedure
Run the method in order
Step 1
Inspect and rinse
Inspect and rinse the conductivity cell or probe according to its instructions.
Record: Note visible residue, cleaning, or probe condition.
Step 2
Verify or calibrate
Measure the specified conductivity standard and complete calibration if the instrument or SOP requires it.
Record: Record standard value, observed value, and pass/fail status.
Step 3
Collect a representative sample
Mix or collect the liquid sample consistently and avoid contaminating it with standard solution or residue from another sample.
Record: Record sample identity and collection method.
Step 4
Measure and stabilize
Place the probe correctly in the sample, allow the reading and temperature compensation to stabilize, and record the displayed EC unit.
Record: Record EC, units, temperature if available, and time.
Step 5
Rinse and close out
Rinse the probe and store it according to its manufacturer instructions.
Record: Record exceptions or maintenance.
Quality control
Verification checks
Reference standard is within the instrument's stated acceptance range.
Units are recorded with every value.
Sampling/extraction method is unchanged when comparing a time series.
Evidence record
Fields to preserve
- meter identification
- standard value
- verification result
- sample identity
- sampling method
- EC and units
- temperature if available
- operator
- notes
Interpretation boundary
Limitations
EC reflects total ionic conductivity, not the concentration of each nutrient ion.
Different meters, units, extraction methods, and temperature handling can make numbers non-comparable unless documented.
Connected learning