19
AQUALAB TDL/TDL 2
Operating Temperature
Minimum
4 °C
Typical
23 °C
Maximum
50 °C
Operating Environment
0%–90% RH noncondensing
Data Communications
USB A and RS-232 serial
9,600–115,000 baud
Power
110–220 VAC
50/60 Hz
COMPLIANCE
Manufactured under ISO 9001:2015
EM ISO/IEC 17050:2010 (CE Mark)
3.2 COMPONENTS
The AQUALAB TDL uses a tunable diode laser to measure the water activity of a sample.
The sample is equilibrated with the headspace of a sealed chamber containing a tunable
laser that shines light of a controlled wavelength at a detector that receives the light from
the laser. At equilibrium, the relative humidity of the air in the chamber is the same as the
water activity of the sample. In the AQUALAB TDL, the vapor pressure of the headspace in
equilibrium is determined by the attenuation of signal strength from the laser caused by the
presence of water vapor in the headspace. This vapor pressure is divided by the saturated
vapor pressure at the sample temperature, which is measured using an infrared (IR) sensor,
to give water activity. The AQUALAB TDL displays the final water activity.
The AQUALAB TDL main components include the display screen and sample chamber
(
