Best with app logging · Light meters

UNI-T UT383BT

by UNI-T

Pocket lux meter that sends readings to a phone app over Bluetooth. 0 to 199,900 lux, ±4% + 8 digits below 10,000 lux, about $35 on Amazon.

Specs

Range0–199,900 lux
Accuracy±(4% + 8) below 10,000 lux
Cosine correctedNot stated
Melanopic readingNo
SensorBuilt-in
Accuracy high±(5% + 10) at 10,000 lux and above
Resolution1 lux below 10,000 lux
Sample rate0.5 s
AppiENV, via Bluetooth
Battery3 × AAA
Weight118 g

Specs from the manufacturer and the sources listed below. Last verified Oct 20, 2026.

Good

  • Bluetooth link to the iENV app for recording, storing and exporting readings
  • An earlier UT383 did well for its price in calibration and spectral response in an independent test against a Class A meter
  • Backlit display with max/min and data hold
  • Small and light at 118 g

Not so good

  • Sensor is built into the body, so your hand or head can shade it
  • The +8 digit error term swamps dim readings: at 10 lux the spec allows about ±8 lux
  • No cosine correction stated
  • One forum user reported their unit reading more than 10% low

The UT383BT is the cheapest way to see how light changes over a day rather than at one moment. It sends readings over Bluetooth to UNI-T’s iENV app, which records, stores and exports them. Leave it on a windowsill or desk and you get a picture of when the room is bright and when it drops off, which is hard to judge by eye.

Specs are typical for a budget meter: 0 to 199,900 lux, ±(4% + 8 digits) below 10,000 lux and ±(5% + 10 digits) above, with a reading every half second. That covers SAD lamps and daylight.

It is weak at the dim end. The fixed 8-digit term means that at 10 lux, the evening limit in the 2022 consensus targets, the spec allows an error of about ±8 lux, so treat bedroom readings as a rough guide only.

Independent data is limited but encouraging. In a 2018 Budget Light Forum comparison against a MobiLux Class A meter, the tester said an earlier UT383 did “not do a bad job actually both in calibration and wavelength response” for its price. A commenter in the same thread found their unit read more than 10% low. The BT version first appeared on Amazon in late 2021, after that test, so it is not certain the hardware is identical.

The sensor is built into the top of the body. That keeps it pocketable, but you need to hold it away from your face and keep your fingers clear, or rest it on something at eye height.

Amazon is the easiest place to buy it in the US. If you want a separate sensor probe instead of logging, the Dr.meter LX1330B has one a separate sensor probe for about $10 more.

Sources

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