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Distillation unit · Calibration procedure

Temperature sensor verification

Compares the distillation unit's temperature sensor with a calibrated reference at several points across the working range, and checks performance by distilling a pure compound.

Photo of a Distillation unit
Photo: Oilguy86, CC BY-SA 3.0 (cropped), via Wikimedia Commons
PURPOSE

Why this is checked

Every reported distillation temperature (IBP, T10, T50, T90, FBP) depends on the temperature sensor. Electronic sensors can drift, and automatic units apply a lag correction to mimic mercury thermometers. Verifying the sensor against a traceable reference, and running a pure-compound distillation, confirms both the sensor and the lag behaviour.

Frequency

Typically every 6–12 months for the reference comparison, and more often (for example monthly) for the pure-compound or check-sample distillation, or after sensor replacement.

Learn how the Distillation unit works
YOU WILL NEED

Standards & tools

  • Calibrated reference thermometer (Pt100 or thermocouple) traceable to national standards
  • Dry-block or stirred oil calibrator covering about 0–400 °C
  • Pure compound for performance check (for example toluene, and a higher-boiling compound such as hexadecane) with the expected values given in the current D86
BEFORE YOU START

Prerequisites

  • Reference thermometer calibration certificate in date
  • Instrument in service mode so raw sensor readings can be seen (lag correction off for the static comparison)
  • Sensor and calibrator inserts clean
PROCEDURE

Step by step

  1. 1Remove the sensor from the flask holder (or as the manufacturer describes) and insert it with the reference probe into the calibrator.
  2. 2Set the calibrator to the first point (for example 100 °C) and wait until both readings are stable.
  3. 3Record the reference and unit readings; repeat at further points across the range (for example 200 °C and 300 °C, and lower or higher as used).
  4. 4Calculate the error at each point (unit − reference).
  5. 5Refit the sensor at the correct position (top of bulb level with the lower edge of the side-arm).
  6. 6Distil the pure compound under the stated conditions and compare the result with the expected value in the current method.
RECORD

Example observation table

Set point (°C)Reference (°C)Unit sensor (°C)Error (°C)
100100.02100.30+0.28
200200.05200.40+0.35
300300.10299.70−0.40
CALCULATION

How to calculate the result

Formula
Error = unit reading − reference reading
Worked example
  1. 1

    At 100 °C: 100.30 − 100.02 = +0.28 °C.

  2. 2

    At 200 °C: 200.40 − 200.05 = +0.35 °C.

  3. 3

    At 300 °C: 299.70 − 300.10 = −0.40 °C.

  4. 4

    Largest error = 0.40 °C, within an illustrative SOP limit of ±0.5 °C — pass.

ACCEPTANCE CRITERIA

Pass if

  • Error at each point within the limit in your SOP (commonly about ±0.5 °C).
  • Pure-compound distillation within the tolerance given in the current method.
  • Check sample within control-chart limits.
IF IT FAILS

What to do

  • Check sensor connections and position, then repeat.
  • Apply a correction or recalibrate the sensor if the software allows and the SOP permits.
  • Replace the sensor if errors are large or unstable, and repeat verification.
  • Do not report results until the sensor passes; assess results since the last good check.
In LimsPulse · Calibration Management

LimsPulse schedules this calibration, records the result against limits, and blocks the instrument everywhere if it fails or goes overdue.

See how