Objective: Ensure equipment is ready and safe to use.
Inspect the Thermocouple:
Check for physical damage (cracks, corrosion, or broken wires).
Clean the sensor tip if contaminated.
Verify Equipment:
Confirm the calibration furnace and reference sensor (e.g., PRT) are functional and within their calibration period.
Ensure the data acquisition system (multimeter, data logger) is operational.
Safety Measures:
Wear heat-resistant gloves and safety goggles.
Ensure proper ventilation for high-temperature furnaces.
Objective: Position sensors correctly for uniform heating.
Insert Sensors:
Place the thermocouple and reference sensor at the same depth in the furnace’s uniform temperature zone.
Use thermal wells or protective tubes to shield sensors from contamination.
Electrical Connections:
Connect the thermocouple to the data logger using shielded cables to minimize electrical noise.
Ensure tight connections to avoid voltage drops.
Configure the Furnace:
Set target calibration temperatures (e.g., low, mid, and high points within the thermocouple’s range).
Objective: Achieve thermal equilibrium.
Heat the Furnace:
Ramp the furnace to the first calibration temperature.
Allow sufficient time for stabilization (e.g., 30 minutes for high-temperature furnaces).
Monitor Stability:
Track the reference sensor’s readings until fluctuations are ≤ ±0.1°C of the setpoint.
Objective: Capture accurate data at each calibration point.
Record Reference Temperature:
Note the stabilized temperature from the reference sensor (e.g., PRT).
Measure Thermocouple Output:
Record the thermocouple’s voltage (mV) or temperature reading.
Repeat:
Conduct measurements at 3–5 temperature points across the thermocouple’s operating range.
Objective: Evaluate thermocouple performance.
Calculate Errors:
Error = Thermocouple reading – Reference temperature.
Compare to Standards:
Check if errors fall within tolerances specified by IEC 60584 or ASTM E230.
Generate Correction Data:
Create an error curve or correction table for the measurement system.
Objective: Maintain traceable records.
Calibration Certificate:
Include: Date, technician name, equipment IDs, calibration points, errors, and compliance status.
Attach error curves or correction factors.
Storage:
Save records digitally and physically for audits (ISO 17025 requirement).
Decision Making:
If errors exceed tolerances, either apply corrections in the data system or replace the thermocouple.
Equipment Care:
Clean the furnace chamber and sensors.
Store thermocouples in a dry, contamination-free environment.
Traceability: Use NIST-certified reference sensors.
Uniformity Check: Validate the furnace’s temperature uniformity annually.
Environmental Control: Shield the setup from drafts and electromagnetic interference.
Regular Maintenance: Clean heating elements and replace degraded insulation.