Built-in Dome Gauges and Probes: What They Show

A built-in gauge reads whatever its sensor touches or sits near. That's usually the air or the metal around the sensor in the dome or door, not the floor you bake on.

Two common kinds

Two common kinds of built-in thermometer are described here. Your manual should say which you have.

Dial gauge. Coiled bimetallic strips are commonly used in mechanical dial thermometers to move a pointer indicating temperature¹. Two metals are bonded together. When they warm, one expands more than the other, and the strip bends or twists. A longer coil gives improved sensitivity¹. There's no battery and no electronics.

Electronic probe. A probe such as a thermocouple joins two different conductors at a measuring junction, with a second, reference junction elsewhere². A small display then shows the converted number. The main limitation with thermocouples is accuracy².

Where the sensor sits

Both kinds share one trait. They're placed in thermal contact with what they measure and have to reach thermal equilibrium with it, as a contact thermometer does³. A gauge in the dome therefore reports the temperature of the spot where its tip sits, once the tip has caught up.

A wood-fired oven is generally built with a cooking floor under a dome⁴. The two parts heat at different speeds. A gauge near the top of the dome will usually say little about the floor under the pizza. That's why the gauge and a gun can differ by a wide margin without either being broken. The gap is explained in the floor and dome page.

Why a gauge can seem to lag

A dial gauge has to heat its own metal. A probe tip has to warm through. Both take some time to settle, so a gauge may show an older figure after the fire changes. Pay attention to how the pointer behaves during a long session. If you're unsure whether a slow climb is normal for your gauge, follow the gauge section of your manual.

What affects the reading

• Position and soot. These effects are general and depend on your oven. Where the sensor sits and a coating of soot can both change what it shows. Your manual says what is normal for your gauge.
• Age. Thermocouples are subject to alloy manufacturing uncertainties and aging effects².
• The dial scale. Some dials have coloured bands rather than numbers. Read your manual for what each band means.

How to use a gauge well

1. Read your manual's page on the gauge. It should say what the gauge measures and where.
2. Note the gauge number whenever you take a floor reading with a gun.
3. Write the pair down, with the time since lighting.
4. After several sessions, look at how the two numbers relate.
5. Use the gauge for the trend, and use the manual's wording for the limits.

A gauge you've compared against the floor a few times becomes a handy signal. You'll learn what number on your own dial goes with a floor that's ready. That's your own oven's pattern, though, not a rule for other ovens.

When to doubt it

Treat it with caution if the pointer sticks, if it won't return to rest when the oven is cold, or if the display jumps about. Compare it with a second thermometer, using the steps in the accuracy page. If a part looks faulty, contact the maker, and don't open or change the oven's parts except as the manual allows.