METER Aqualab TDL, Benchtop Water Activity Meter

The volatility problem

Measuring water activity in samples such as sauces, dressings, spices, or teas has traditionally been difficult. The reason: they contain volatile compounds that interfere with chilled mirror and capacitance sensors.

Laser speed. Laser accuracy. Laser simplicity.

As world experts in water activity, it wasn’t enough to engineer an instrument that directly measured water activity in most foods. So we created the TDL, which uses a laser sensor capable of accurately measuring even the most difficult volatiles. It’s easy to use and takes only minutes to measure any sample—even soy sauce, pure alcohol, and gasoline. The TDL delivers readings you can completely trust, no matter what the sample contains.

Cuts through the volatility problem with laser precision

When it comes to measuring water activity of volatiles, readings don’t get more precise. That’s because the TDL uses a laser tuned to the absorption band of water. The laser beam—less than one nanometer wide—locks on to water molecules no matter what the concentration of volatiles. The TDL is even able to correctly measure the water activity of pure alcohol.

Measuring volatile compounds has never been easy. Until now.

Despite being a complex instrument, the TDL is easy to use. Its sensor has no moving parts and is housed in a fully sealed sample chamber. Best of all, it doesn’t require user calibration. You’re five minutes away from an accurate water activity no matter what the sample is.

Accurate readings in only 5 minutes

The TDL’s laser takes five minutes to make a measurement of most samples. Compared to other instruments that take almost an hour, this adds up to significant time savings and quicker quality measurements no matter what ingredients are in your sample.

Volatility meets its match

Laser accuracy. Low-maintenance usage. Lightning fast measurement. The TDL stands alone, letting you measure water activity in previously impossible-to-measure samples.

Sensor type

Tunable diode laser

Water activity

Range: 0.000–1.000 aw
Resolution: 0.0001 aw
Accuracy: ±0.005
Repeatability: 0.001 aw


25 °C standard
Range: 15-50 °C (with calibration)
Resolution: 0.01 °C
Accuracy: ±0.2 °C

Temperature stability

User-selectable range, internal thermoelectric controlled

Measurement time

Less than 5min

Sample cup capacity

7mL recommended (15mL full)


64 × 128 graphical display with backlighting

Data communications


Program Identification

Alphanumeric, programmable to display product name, lot or product ID number

Data storage

8,000 readings

Case dimensions

Length: 26.7cm
Width: 17.8cm
Height: 12.7cm

Case material

Machined aluminium frame; Lustran 433 (ABS) with fire retardant



Operating temperature

4°C to 50°C

Operating environment

0 to 90% relative humidity (noncondensing)

Universal power

110V to 220 VAC
50/60 Hz


Manufactured under ISO 9001:2015
EM ISO/IEC 17050:2010 (CE Mark)

*Aqualab TDL is calibrated to a NIST traceable temperature standard*

METER Aqualab TDL Brochure


METER Aqualab TDL Full Manual


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