Extech LT300 Digital Light Meter, 400,000 Lux

LT300 is an Extech digital light meter that measures illuminance up to 400,000 Lux or 40,000 foot-candles. A silicon photodiode with a colour-correction filter sits in a remote sensor on a coiled cable, and the meter adds relative, peak, data hold and min/max functions with a backlit display and analogue bargraph.

Lighting surveys from a desk to a stairwell

The sensor is connected permanently by a coiled cable that stretches from 30.5 cm (12 in) to 61 cm (24 in), so the meter body can be held or stood on its tilt stand while the dome sits on a work surface. Five ranges in lux and four in foot-candles are selected with the range button; the display shows OL when a range is exceeded.

Peak mode captures light pulses as short as 10 microseconds, which helps with flashing or pulsed sources, and relative mode shows a reading as a difference from a stored reference, for example comparing a workstation with a reference point after a lamp change.

Features stated in the datasheet and manual

• Up to 40,000 Fc or 400,000 Lux with 0.01 resolution; basic accuracy ± (5 % of reading + 0.5 % of full scale).
• Cosine and colour corrected photodiode; spectral response CIE photopic.
• MIN/MAX, data hold, relative, peak and reset functions; backlight and bargraph.
• Supplied with 9 V battery, sensor with protective cover, protective holster and soft case; an LT300-NIST version with traceable calibration is listed.

Technical specification

Measurement specification (manual)

General specification

Ordering and use

Two order codes are listed: LT300 and LT300-NIST, which comes with a calibration traceable to NIST. The two documents give different body dimensions and weights, probably because the manual quotes the meter inside its rubber jacket; check the carry-case size if it matters for your kit.

Use the range button to select the range that gives the highest resolution without OL, and replace the protective cap whenever the meter is not in use to keep the dome clean.

Measurement and care notes from the manual

Remove the cap to expose the white dome, place the sensor at the working plane height, and read after the display settles. The manual includes a table of typical light levels for factories, offices, hospitals, stores and homes in Lux and Fc, for example 300 to 750 Lux for conference rooms and 750 to 1,500 Lux for clerical work.

Clean the dome with a damp cloth and mild soap only, never solvents. Replace the 9 V battery after removing the protective jacket and the rear compartment screw. Use the reset button to clear relative, hold, peak and min/max modes.

Typical uses

The datasheet names indoor lighting tests and checks of security and safety illumination in parking garages, night-time ATM areas, stairwells, landings and hallways. General engineering note: in Gulf offices, car parks, warehouses and labour accommodation, a handheld Lux survey is a quick way to check LED replacements against the design levels, and the peak function helps with pulsed or dimmed fittings.

Related Extech items

For sound level surveys see the Extech sound level meters, and for moisture or vibration checks the other handheld meters. See the portable test and measurement category.

Field use and calibration notes

Light meters are used in the region for lighting surveys in offices, schools, hospitals, warehouses, factories, car parks and streets, and for checking that lighting meets the design or the applicable standard. Hold the sensor at the working plane height, usually desk or floor level as the standard requires, and avoid casting a shadow on it. For daylight measurements in the region, readings near windows and outdoors can be very high, which is where the wide range of the LT300 is useful.

Keep the sensor cover on when the meter is not in use, clean the sensor gently, and arrange calibration at regular intervals where readings are used for reports or compliance.

Record the measurement points and heights used, so later surveys can be compared directly.

Information to send with an enquiry

• Type of survey and lighting levels
• Calibration certificate requirement
• Quantity

Frequently asked questions

What is the LT300 measuring range?

Up to 40,000 foot-candles or 400,000 Lux, in five Lux ranges and four Fc ranges.

How accurate is it?

Basic accuracy is ± (5 % of reading + 0.5 % of full scale), with CIE photopic spectral response.

Can it capture light pulses?

Yes. Peak hold captures pulses that rise or fall down to 10 microseconds.

Is the sensor detachable?

No. The light sensor is permanently attached to the meter by a coiled cable, expandable from 30.5 cm to 61 cm.

Is Seven Star LLC an Extech distributor?

No. Seven Star LLC is not an Extech distributor; it is an independent Muscat-based supplier that quotes Extech products on request.

Documents and quotation

Need LT300? The Extech datasheet and user manual are attached to this listing. Seven Star LLC (independent supplier, Muscat) can quote the item and arrange supply on request; list quantity and site location in your enquiry. Verify the order code and electrical options in the documents before ordering. Other products are in the category page.