Err or Er with a number (thermometer error code)
The thermometer found a fault in itself, or in the way the reading was taken, and will not give a temperature. What a number means is set by each maker: Er 2 on a Microlife NC 200 means the thermometer was held against the forehead, not that it is broken.
Check your thermometer’s manual — makers differ.
What it is for
Look the code up in your own manual, or in the tables below for the models read. Most makers say to restart the thermometer first: Omron (ET720) says “Remove the battery, wait for 1 minute, and reinsert the battery again”, and Braun (ThermoScan) “Wait 1 minute until the thermometer turns off automatically, then turn on again”, then to reset it by taking the batteries out and putting them back. If the error stays, each of them says to contact its customer service. For the MT 410 stick thermometer, Microlife says that after an ERR at switch-on “the thermometer must be replaced”.
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
- Err, ERR or Er with a number where the reading should be. Braun thermometers flash their self-check screen instead of showing a code.
- Names makers use
- ERR (Microlife MT 410); Er 0, Er 2, Er 6 (Microlife NC 200); Errors 5 to 9 (Omron ET720); Error (Withings Thermo); Flashing self-check display (Braun ThermoScan and No touch)
Where makes differ
Only some codes are faults. On the Microlife NC 200, Er 0 and Er 6 are system faults but Er 2 means the thermometer touched the forehead or object, and Microlife says to keep 1 to 5 cm away. Omron lists Errors 5 to 9 on the ET720 as malfunctions of the unit. Withings uses one word, Error, both for a system error and for a reading outside its range, so on a Withings Thermo an Error can simply mean a reading to take again. Microlife’s IR 310 manual adds a sound: three short beeps for a system error or malfunction.
The codes, maker by maker
| Code | What it means | What to do |
|---|---|---|
| H | “too high, measured temperature is higher than 43 °C / 109.4 °F in body mode or 99.9 °C / 211.8 °F in object mode” | “Make sure the measuring sensor is clean. Then, take a measurement again.” |
| L | “too low, measured temperature is lower than 34 °C / 93.2 °F in body mode or 0.1 °C / 32.2 °F in object mode” | “Make sure the measuring sensor is clean. Then, take a measurement again.” |
| AH | “ambient temperature is higher than 40.0 °C / 104.0 °F” | Leave the thermometer in the room for at least 30 minutes within its range, then measure again. |
| AL | “ambient temperature is lower than 15.0 °C / 59.0 °F in body mode or lower than 5.0 °C / 41.0 °F in object mode” | Leave the thermometer in the room for at least 30 minutes within its range, then measure again. |
| Er 0 / Er 6 | “The system has a malfunction.” | Remove and reload the battery and restart the thermometer; if the message still appears, contact the Microlife retailer or distributor. |
| Er 2 | “Device is directly placed on the forehead / object.” | “Keep the measuring distance of 1 - 5 cm.” Do not touch the sensing area. |
| Battery symbol alone | “The battery is low.” | “The battery should be replaced immediately.” |
| Code | What it means | What to do |
|---|---|---|
| Lens filter symbol | “No lens filter is attached.” | “Attach new, clean lens filter.” |
| POS | “The thermometer probe was not positioned securely in the ear.” | Check that the probe sits correctly and stays still; replace the lens filter, reposition and press Start. |
| Room temperature message | Ambient temperature outside the operating range, 10 – 40 °C (50 – 104 °F). | Leave the thermometer for 30 minutes in a room between 10 and 40 °C. |
| HI / LO | “Temperature taken is not within typical human temperature range (34 – 42.2 °C or 93.2 – 108 °F).” | Clean the probe tip and lens, fit a new lens filter, insert the thermometer properly and take a new temperature. |
| Flashing self-check display | “System error”: the self-check display flashes continuously and no ready beep follows. | Wait 1 minute for it to turn off and turn it on again; then reset it by removing and replacing the batteries; then contact the service centre. |
| Battery symbol | “Battery is low, but thermometer will still operate correctly” — or, in its second state, “Battery is too low to take correct temperature measurement.” | “Insert new batteries.” |
What it does not mean
An error code is not a temperature and is not Lo or Hi. It does not always mean the thermometer is broken: Microlife’s Er 2 and Withings’ out-of-range Error are measuring problems.
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:
- Microlife: Microlife MT 410 digital stick thermometer — instruction manual (IB MT 410, revision 2025-07-03, PDF) — Function test: “If a malfunction is detected (measurement inaccuracy), this is indicated by «ERR» on the display, and a measurement becomes impossible. In this case, the thermometer must be replaced.” Checked 2026-09-29.
- Microlife: Microlife NC 200 non-contact thermometer — instruction manual (IB NC 200-e N-V10, 2026-08-17, PDF) — Error messages table: «Er 0» / «Er 6» system malfunction, «Er 2» device directly placed on the forehead or object, H, L, AH, AL, blank display and flat battery, each with its solution. Checked 2026-09-29.
- Microlife: Microlife Ear Thermometer IR 310 — instruction manual (IB IR 310 N-V10, revision 2024-09-13, PDF) — Error function display: “The system has a malfunction”; technical specifications, acoustic: “System error or malfunction: 3 short beeps”. Checked 2026-09-29.
- Omron: Omron No-Touch Forehead Thermometer ET720 (MC-720-Z) — instruction manual (US, 5681249-5D, PDF) — The Icons and Error Messages: “Errors 5 - 9 indicate a malfunction of the unit. Remove the battery, wait for 1 minute, and reinsert the battery again. If the message still appears, please contact OMRON customer service.” Checked 2026-09-29.
- Braun: Braun ThermoScan 7 (IRT 6520) and ThermoScan 3 (IRT 6030) infrared ear thermometers — instruction manual (Asia-Pacific, PDF) — Errors and troubleshooting: system error, self-check display flashes continuously; wait 1 minute, then reset by removing the batteries, then contact the service centre; plus POS, lens filter, ambient, HI/LO and battery rows. Checked 2026-09-29.
- Withings: Withings Thermo — regulatory information and troubleshooting (PDF) — Troubleshooting table: “Error” for a temperature outside ranges, and “Error” for a system error — “Contact customer service”. Checked 2026-09-29.
Written in our own words; quotations are the makers’ wording.