Lens filter or probe cover symbol (cover missing)
The ear thermometer wants a new, clean cover on its probe before it measures. The Braun ThermoScan will not measure at all without one.
Check your thermometer’s manual — makers differ.
What it is for
Fit a new cover of the kind your manual names. Braun says to “always use this thermometer with a new, clean lens filter attached” and to use only “genuine Braun ThermoScan lens filters (LF 40)”. Microlife says: “Only use this thermometer with a new Microlife branded and undamaged probe cover to prevent cross-infection.”
These pages report what each maker’s manual says and quote it wherever health is involved. They do not diagnose anything, they are not medical advice, and they do not tell you whether a temperature is a fever or what to do about it; only your own thermometer’s manual and your doctor or nurse can do that for the person you are looking after.
- What it looks like
- A small probe-cover or filter shape that blinks on an ear thermometer, sometimes with the screen turning red.
- Names makers use
- Lens filter indicator (Braun ThermoScan); Probe cover icon (Microlife IR 310)
Where makes differ
Braun’s ThermoScan manual says the lens filter indicator blinks to show a filter is needed, and that the thermometer “will not work unless a lens filter is attached”; if one was ever used without a filter, Braun says to wipe the probe tip gently with alcohol and let it dry first. Microlife’s IR 310 manual shows the probe cover icon “with a red LCD backlight”, the same red it uses for its fever alarm. Forehead thermometers have no cover at all: Omron and Withings say instead not to touch the lens.
What it does not mean
A red screen with this symbol does not mean a fever on the Microlife IR 310: no reading has been taken yet. The symbol is not a fault, and a new cover clears it.
Other symbols with the same shapes
Sources
No published standard we could check defines the symbols on a digital thermometer’s display, so this meaning is taken from 4 makers’ own manuals and support pages, each fetched and read on the date shown:
- Braun: Braun ThermoScan 7 (IRT 6520) and ThermoScan 3 (IRT 6030) infrared ear thermometers — instruction manual (Asia-Pacific, PDF) — “The lens filter indicator will blink to signal one is needed”; “Note: The Braun ThermoScan will not work unless a lens filter is attached”; error table: “No lens filter is attached. Attach new, clean lens filter.”; care and cleaning after use without a filter. Checked 2026-09-29.
- Microlife: Microlife Ear Thermometer IR 310 — instruction manual (IB IR 310 N-V10, revision 2024-09-13, PDF) — No probe cover on the measuring sensor: “Displays probe cover icon with a red LCD backlight to remind the user to put on a new undamaged probe cover before each measurement.” Checked 2026-09-29.
- Omron: Omron No-Touch Forehead Thermometer ET720 (MC-720-Z) — instruction manual (US, 5681249-5D, PDF) — Safety: “DO NOT touch the probe lens with a finger or breathe on it”; the probe lens cap and how to clean the probe lens. Checked 2026-09-29.
- Withings: Withings Thermo — user guide (v2.0, April 2018, PDF) — Safety: “Do not touch the lens as you might damage it”; cleaning the lens with a cotton swab moistened with warm water. Checked 2026-09-29.
Written in our own words; quotations are the makers’ wording.