Disposable Thermocouple Operating Guide

Disposable thermocouples are single-use — many operators think it's just "insert, read, pull out." But with the same batch of heads, why do some get stable readings and others erratic ones? All in the details.

Step 1: Inspect the Head

Check three things: plastic seat cracks; quartz tube damage; exposed/oxidized wire. Any problem means discard — meaningless reading and possible lance damage. Also match type: S lance with S heads.

Step 2: Correct Insertion

Depth: 300~500mm below the surface. Too shallow reads surface/slag temperature — 20~30°C low.

Angle: vertical or within 15° forward tilt. Never horizontal from the furnace door.

Speed: quick and decisive. Hesitation heats the head in fume before it reaches steel.

Step 3: Dwell and Read

Hold 3~5 seconds for thermal equilibrium. The meter beeps and locks the reading. Too short = low reading; beyond 8 seconds the tube erodes.

Step 4: Withdraw and Record

Pull out right after the reading locks. Discard used heads properly. Record temperature with heat number and time.

Error Checklist

• Low reading → insufficient depth / wrong angle / short dwell
• Unstable reading → damp head / oxidized wire / loose contact
• Err display → damaged head / type mismatch / broken cable

Summary

Disposable thermocouple accuracy is half product, half operation. Deep, fast insertion with 3~5s dwell and matched type — that's the formula.