ATTEN ST-1090 Soldering Tip Thermometer

An instrument for one question: what temperature is the tip of the iron actually at? A soldering station shows what its own sensor inside the heater thinks, and that is not what reaches the end of the tip. A worn tip, oxide in the socket, a tip that does not sit tight — and the station says 350 °C while the tip is at 300 °C. That is exactly why solder “suddenly stops flowing” on a station that looks perfectly healthy.

The ST-1090 answers it in five seconds: touch the tip to the thermocouple on the panel and read the number.

How the sensor works

On the panel sits a replaceable three-contact sensor: two posts with a thin 0.2 mm wire strung between them, coated in lead-free solder.

The coating is the point. A bare K-type thermocouple does not wet with solder — it rejects it, and you get no thermal contact with the tip. A tinned wire wets, and then it reads the temperature of the tip rather than of the air beside it.

Three contacts instead of two mean the tip lands on the wire at any angle, so you do not have to aim the iron carefully.

Hence the sensor being replaceable: the wire is consumable. It lasts around 50–60 touches, after which the coating burns off, the wire oxidises and the readings drift. The instrument counts the measurements and warns when the sensor is due for replacement.

How many touches the sensor has already done is on the display itself: the small number in the corner above the temperature. That is how you see how much life is left in it.

The external thermocouple

On the side there is an External K socket for an ordinary K-type thermocouple, which is how you measure everything else: air from a hot-air gun, a preheater, a heatsink, a mould in an oven.

One catch: for the external thermocouple to work, the three-contact sensor has to come off the panel. While it is in place it stays in the circuit, and the instrument reads it instead of whatever you plugged in.

What it is good for

• Checking whether the station's setpoint matches what the tip is actually at
• Finding the offset and working with it, if the station is wrong by a consistent amount
• Comparing tips against each other and retiring the dead ones
• Seeing how far the temperature sags under load, when the tip meets a large thermal mass
• With the external thermocouple: hot-air guns, preheaters and anything else up to 800 °C

How to use

1. Switch on with POWER.
2. Let the iron come up to temperature and sit there for a few minutes — a measurement taken right after switching on means nothing.
3. Leave a small bead of solder on the tip: it improves thermal contact with the wire.
4. Touch the tip to the thermocouple on the panel and hold. The instrument gives no sign that the measurement is over — treat it as over when the reading has not changed for 5–10 seconds. MAX HOLD keeps the peak, RESET clears it.
5. Compare with what the station is set to.
6. Take the tip away as soon as the reading settles. Extra seconds on the sensor are its life.

How not to break it

• Do not press the tip onto the wire: it is thin and breaks under pressure, not under heat.
• Do not drag the tip sideways across the sensor.
• Do not hold the iron on the sensor longer than needed — it is consumable and counted.
• Plug the external thermocouple in the right way round; the polarity is marked on the case.

What is in the container

The instrument, spare three-contact sensors and the external K-type thermocouple live together in a plastic container on the shelf. The sensor is consumable, so change it yourself — the spares are right there. Everything goes back into the same container.

Renting it

This one goes home with you, usually to check your own iron or station without carrying it to the hackspace. Booked on the site, picked up by the code on the sticker at any hour. The daily rate and the term are in the rental block on this page.

Access

The container is in the hackspace room, so a plan that includes hackspace access is required. No induction is needed.