EXTECH SDL400 Light/Lux Meter / Datalogger to SD Card

When “I Think the Lighting’s Fine” Isn’t Good Enough

In workplaces governed by Safe Work Australia guidelines and the Building Code of Australia (BCA), lighting compliance isn’t a matter of opinion — it’s a documented obligation. Whether you’re conducting an office ergonomic assessment, commissioning a new industrial facility, verifying emergency lighting performance, or completing a building energy audit, you need measured lux values, not estimations.

The problem with basic light meters is that they only tell you what’s happening right now. You get a snapshot, jot down a number, move on. If someone later questions your results — or if lighting conditions change across a shift — there’s nothing to back you up. What you actually need is continuous, timestamped light data that you can export, review, and attach to a compliance report without spending hours reformatting spreadsheets.

That’s exactly what the Extech SDL400 Light Meter and Datalogger is built to do.

Continuous Light Measurement with Automatic Data Capture

The SDL400 isn’t just a lux meter — it’s a field-ready datalogger that removes the manual bottleneck from illuminance measurement entirely. Insert the included SD card, set your sampling interval anywhere from once per second to once per hour, and the instrument takes care of the rest. Every reading is date- and time-stamped, then written directly to the card in a format that opens straight into Microsoft Excel — no conversion software, no proprietary apps, no USB adaptor juggling.

For compliance professionals who need to demonstrate lighting conditions over time — across a full work shift, during commissioning, or as part of a periodic workplace inspection — this is a genuine workflow improvement. You’re not just measuring; you’re automatically generating the evidence trail.

The onboard memory holds up to 99 manual readings for quick spot-checking, while the SD card expands that to an extraordinary 20 million data points. In continuous logging mode with a 2G card, you can leave the SDL400 running for extended monitoring tasks without intervention.

Measurement Range That Covers the Full Spectrum of Australian Work Environments

From dimly lit server rooms and archive storage areas to high-bay industrial warehouses and outdoor construction sites in full Australian sun, the SDL400 spans a measurement range capable of capturing it all:

• Lux (metric): 2,000 / 20,000 / 100,000 Lux across three auto-selectable ranges
• Foot Candles (imperial): 200 / 2,000 / 10,000 Fc for projects requiring US or legacy documentation formats
• Basic accuracy: ±4% of reading — sufficient for most workplace and building compliance applications

The light sensor incorporates a precision silicon photodiode with a cosine-corrected and colour-corrected spectral response filter. That matters in practice: without cosine correction, a meter tilted even slightly from the light source will return artificially high or low readings. Without colour correction, fluorescent, LED, and high-pressure sodium sources skew results. The SDL400 compensates for both, returning values that genuinely reflect how a human eye perceives the light environment — which is precisely what workplace lighting standards are designed to assess.

The 1.1-metre cable between the meter body and the light sensor head means you can position the sensor correctly at workplane height while keeping the display where you can read it comfortably. The protective cover keeps the sensor clean between measurements — a small detail that makes a real difference when you’re moving between dusty industrial environments.

Temperature Logging: A Bonus Channel for Building and Environmental Audits

Many lighting assessments are conducted as part of a broader workplace or building audit. The SDL400 recognises this by including a dedicated thermocouple input that simultaneously logs ambient temperature alongside illuminance — all to the same SD card file.

• Type K thermocouple: -100°C to 1300°C
• Type J thermocouple: -100°C to 1200°C

This makes the SDL400 a genuinely multi-purpose audit tool. HVAC technicians conducting energy audits, environmental health officers inspecting cold storage compliance, and building inspectors assessing thermal comfort can log both light and temperature in a single pass. Optional thermocouple probes are available separately to suit different measurement environments.

Built for the Field — Not Just the Lab

The SDL400 is packaged with practical field use in mind. It ships complete and ready to work:

• 6 × AA batteries installed (no waiting for a charge)
• SD card included
• Hard carry case for protection between sites
• Backlit LCD for readability in low-light spaces
• Data Hold function to freeze a reading while you note context
• Auto power-off to preserve battery life on extended deployments (can be disabled for unattended logging)
• MIN/MAX record and recall for identifying lighting peaks and troughs across a measurement session

The offset adjustment function allows you to zero the meter against a reference condition — useful for making relative measurements in environments where you’re comparing against a baseline rather than an absolute value.

NIST-Traceable Calibration Option

For applications where calibration traceability is a non-negotiable requirement — NATA-accredited inspections, formal WHS compliance audits, or building commissioning sign-offs — the SDL400-NIST variant ships with a Certificate of Calibration traceable to NIST (National Institute of Standards and Technology) standards. This is the version to specify when your client, insurer, or regulator requires documented calibration evidence alongside measurement data.

Not sure which variant suits your situation? Our team is happy to advise.

Who Uses the Extech SDL400?

Workplace Health & Safety Officers and Facility Managers — Conducting periodic illuminance assessments to verify compliance with AS/NZS 1680 Interior Lighting standards across offices, warehouses, and production floors.

Electrical Contractors and Building Commissioning Teams — Verifying that installed lighting systems meet design lux levels during NCC (National Construction Code) sign-off, particularly for commercial and industrial projects.

Energy Auditors — Logging light levels across shifts and areas to identify over-lit zones where dimming or zoning controls could reduce energy consumption.

HVAC and Environmental Technicians — Conducting combined light and temperature surveys during building audits, using a single instrument rather than two separate meters.

Lighting Designers and Architects — Validating that installed luminaire layouts achieve designed lux targets before client handover.

Occupational Hygienists and WHS Consultants — Gathering time-series illuminance data to support formal workplace lighting reports and risk assessments.

Educational Institutions (TAFE and RTOs) — Teaching students practical illuminance measurement techniques with an instrument that demonstrates real-world datalogger workflows.

What’s in the Box

• Extech SDL400 Light Meter / Datalogger
• Light sensor with 1.1m (45″) cable and protective cover
• SD card (2G)
• 6 × AA batteries (installed)
• Hard carry case
• User manual

SDL400-NIST version includes: Certificate of Calibration Traceable to NIST

Optional accessories available: Type J bead wire probe (model 872502), Type K bead wire probe (TP870), Type K clamp probes (TP200, TP400), and 100–240V AC adaptor (UA100-240) with AU/US/EU/UK plugs.

TECHNICAL SPECIFICATIONS

APPLICATIONS & USE CASES

1. Workplace Lighting Compliance Audits (AS/NZS 1680)

Australian employers are obligated to provide adequate lighting for the tasks performed in their workplaces. AS/NZS 1680 sets out minimum lux levels by task type — from 80 Lux in storage areas to 750 Lux or more for fine detail work. The SDL400’s automatic SD logging lets WHS officers conduct a full-shift illuminance survey, capturing how lighting levels vary across the working day as daylight contribution changes — something a single spot measurement can never reveal.

2. Commercial and Industrial Building Commissioning

Lighting systems in new commercial and industrial buildings must be verified against design lux levels before client handover under the NCC. The SDL400 allows commissioning teams to systematically measure and document illuminance across every zone, with all data automatically timestamped and exportable to Excel for inclusion in handover documentation packages.

3. Energy Audit and Lighting Upgrade Projects

When assessing a facility for LED lighting upgrades or automated daylight-harvesting controls, energy auditors need to understand existing light levels across different times of day and zones. The SDL400’s adjustable logging interval means you can profile an entire facility over a business week before sizing controls or specifying replacement luminaires — ensuring the upgrade is based on actual measured data, not assumptions.

4. Emergency and Exit Lighting Verification

Australian Standard AS 2293 governs emergency lighting performance, including minimum maintained illuminance levels on escape paths. The SDL400 allows lighting contractors and facility managers to measure and record exit lighting lux values as part of periodic testing, creating a documented record that can be presented during regulatory inspections.

5. HVAC and Environmental Site Audits

When conducting a combined environmental assessment — looking at thermal comfort and lighting together — the SDL400 eliminates the need for two separate instruments. Connect a Type K thermocouple, and both light level and ambient temperature are logged simultaneously to the same SD card file, simplifying data analysis and report generation.

6. Horticulture and Controlled Environment Agriculture

Plant growth under artificial lighting depends on achieving consistent light levels (measured in lux or PPFD). While the SDL400 isn’t a PAR meter, it provides a reliable baseline for monitoring growth-room lighting consistency, identifying failing lamps or shading problems before crop yield is affected.

7. Training and Educational Applications

TAFEs and registered training organisations (RTOs) delivering electrical, building, or environmental health training need instruments that teach real-world workflows. The SDL400’s datalogger functionality exposes students to the complete measurement-to-report pipeline — from instrument setup, through data capture, to Excel analysis — in a single practical exercise.

What is a light meter datalogger? A light meter datalogger is an instrument that both measures illuminance (in Lux or Foot Candles) and automatically records those measurements over time with date and time stamps. Unlike a basic light meter that only shows a live reading, a datalogger stores a continuous history of light levels to internal memory or an SD card. This allows professionals to demonstrate how lighting conditions change across a work shift, verify compliance over time, and export data directly into Excel or other reporting tools — without manual note-taking.

What is a lux meter used for in a workplace? In Australian workplaces, a lux meter is used to verify that artificial and natural lighting meets the minimum levels required by AS/NZS 1680 (Interior Lighting) for the type of work being performed. WHS officers, facility managers, and electrical contractors use lux meters to conduct compliance surveys, identify areas where lighting is insufficient or excessive, and generate documented evidence for safety audits, building commissioning, or energy efficiency assessments.

What is cosine correction on a light meter? Cosine correction on a light meter means the sensor is designed to account for the angle at which light hits the measurement surface. In a real space, light arrives from multiple angles simultaneously. A cosine-corrected meter weights those contributions in proportion to the cosine of their angle from vertical — mimicking how a horizontal surface like a workplane actually receives illumination. Without cosine correction, a light meter held at even a slight tilt can report significantly different values from the true ambient illuminance.

What does NIST-traceable calibration mean for a measuring instrument? NIST-traceable calibration means the instrument has been calibrated against reference standards that are directly linked to the National Institute of Standards and Technology — the US body responsible for maintaining the fundamental measurement standards used globally. A NIST-traceable calibration certificate provides documented evidence of that chain of traceability, giving clients, regulators, and auditors confidence that the measurement values produced by the instrument are accurate within stated tolerances. In Australia, NIST traceability is widely recognised alongside NATA (National Association of Testing Authorities) accredited calibration as a credible standard for compliance measurement work.