How Microwave Sensor Cooking Works

Microwave sensor cooking uses a humidity sensor to detect the steam food releases as it heats, and uses that moment to decide how much longer to cook. When it works, you get reheated leftovers or steamed vegetables without guessing at the time; when the food is covered wrong or the cavity is wet, the sensor can be fooled.

How it works, step by step

1. You choose a sensor program. It might be Sensor Reheat or a pad named for a food, such as potatoes or vegetables. On many models the program starts without a time entry.
2. The microwave starts heating. The program sets the power level for that kind of food.
3. Air from the cavity passes the sensor. The fan moves air out of the cavity past a humidity sensor.
4. Food starts releasing steam. As the food heats, moisture escapes. Whirlpool's explainer says the sensors measure the amount of steam or moisture in the cavity.
5. The control sets the remaining time. A GE owner's manual for the JVM1665 over-the-range microwave, hosted on ManualsLib, says the sensor detects the increasing humidity released during cooking and the oven adjusts the cooking time to the type and amount of food. Whirlpool says the sensors adjust cooking time and power automatically.
6. It stops on its own when the program decides the food is done.

What you'll notice because of it

• No countdown at first on many models, just the food name, because the oven doesn't yet know how long it will take.
• Different times for the same button depending on how much food is in the dish and how cold it started.
• Better results with a loose cover. Whirlpool recommends a loose-fitting, microwave-safe lid with a gap so moisture can escape and reach the sensor.
• Foods that suit it. Whirlpool lists vegetables, potatoes, fish, popcorn, pizza, and soups and stews.

Where it can go wrong

Food comes out overcooked

Symptom: dried-out edges or a rubbery texture. A tightly sealed container traps the steam. The GE manual says never to use tight-sealing plastic containers because they can keep steam from escaping and cause food to overcook. It also warns that running a sensor program twice in a row on the same food can overcook or burn it; add time with regular Time Cook instead.

Food comes out underheated

Symptom: a cold center. Water on the outside of the dish or inside the cavity can turn to steam early and mislead the sensor. The same GE manual says to make sure the outside of containers and the inside of the microwave are dry.

Readings thrown off by the metal shelf

Symptom: inconsistent results on models with a removable rack. The GE manual notes that using the metal shelf with Auto Cook is not recommended.

A failed sensor

Symptom: every sensor program ends almost immediately, runs far too long, or shows an error, while manual time cooking works fine. The sensor sits near high-voltage parts, so testing or replacing it is a job for a technician.

Getting the most out of it

• Cover food with a lid or vented plastic wrap, leaving a gap, as the GE manual and Whirlpool both advise.
• Dry the outside of the dish and wipe the cavity before using a sensor program.
• Take the metal rack out first if your model has one.
• Use the sensor pads for the foods they are designed for, and manual time for very small portions.
• If food needs more heat after a sensor program, finish it on Time Cook rather than running the sensor program again.

If sensor programs fail on every food while manual cooking works, a technician who services GE microwaves and other brands can test the sensor safely. For what the power setting itself changes inside the oven, see how microwave power levels work.

Sources

• Whirlpool: How does microwave sensor cooking work?
• GE JVM1665 owner's manual, sensor features (via ManualsLib)

Worth knowing: A sensor program needs a loose cover and a dry dish; most "wrong time" results come from one or the other.

When every sensor program misfires but Time Cook works normally, the sensor itself is the suspect. Call ProFix Miami at (786) 723-6874.