Conductivity meter · Calibration procedure
Conductivity standard check
Measures one or more certified conductivity standards as samples to verify the meter and cell read correctly after calibration.
PURPOSE
Why this is checked
A verification with an independent standard confirms the whole system, including cell constant, temperature handling and electronics, gives correct conductivity values.
Frequency
Before use or weekly / monthly, and after each cell-constant calibration, as defined in your SOP.
Learn how the Conductivity meter worksYOU WILL NEED
Standards & tools
- Certified conductivity standards from a different lot than the one used for calibration, e.g. 146.9 µS/cm and 1413 µS/cm at 25 °C
- Calibrated reference thermometer (for the temperature check)
BEFORE YOU START
Prerequisites
- Cell constant up to date in the meter
- Temperature compensation set to the reference temperature of the standard (25 °C) with the coefficient stated on the certificate, or measure at exactly 25 °C
PROCEDURE
Step by step
- 1Rinse the cell with portions of the first standard and discard them.
- 2Measure a fresh portion and record conductivity and temperature when stable.
- 3Repeat with the second standard.
- 4Compare the temperature reading with the reference thermometer in the same beaker.
- 5Calculate the % error for each standard.
RECORD
Example observation table
| Standard (µS/cm at 25 °C) | Observed (µS/cm) | % error | Meter temp. (°C) | Reference temp. (°C) |
|---|---|---|---|---|
| 146.9 | 147.8 | +0.61% | 25.1 | 25.0 |
| 1413 | 1408 | −0.35% | 25.0 | 25.0 |
CALCULATION
How to calculate the result
% error = (Observed − Certified value) ÷ Certified value × 100
- 146.9 µS/cm standard reads 147.8 µS/cm
- % error = (147.8 − 146.9) ÷ 146.9 × 100 = +0.61%
ACCEPTANCE CRITERIA
Pass if
- Observed value within the tolerance in your SOP, commonly within ±2% (some labs use ±3% or the certificate's uncertainty plus meter accuracy).
- Temperature within ±0.5 °C of the reference (USP <645> requires temperature measurement good to at least ±2 °C).
IF IT FAILS
What to do
- Repeat with a fresh portion of standard and a well-rinsed cell.
- Re-determine the cell constant and repeat the check.
- If it still fails, take the meter out of use and investigate results since the last pass.
MORE
Other Conductivity meter calibrations
In LimsPulse · Calibration Management
LimsPulse schedules this calibration, records the result against limits, and blocks the instrument everywhere if it fails or goes overdue.