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LAUDA TVT

Drop volume tensiometer for measuring surface and interfacial tension

Lauda TVT

Highly precise measurement, low sample volume requirements, modern electronics
LAUDA drop volume tensiometers serve to measure the surface and interfacial tension of liquids. The method is especially suited to determining dynamic interfacial tensions. Here, the volume of a drop detaching from the needle is measured very precisely. The surface/interfacial tension is derived from this depending on whether the drop forms in air or in a second nonmiscible phase (oil).

This measurement principle is in an easy-to-operate measuring unit using precision mechanics and modern electronics. The micro-liter-precise drop formation ensures the outstanding precision and reproducibility of the measured values. With the highly stable Phase-Locked Loop (PLL) speed controller of the direct-current motor, drops can be formed with a lifespan from one second up to a number of hours without vibrations. The analysis of these effects is especially important when it comes to time-limited surfactant effects, like, for example, with quick coating processes, drop formation, wetting processes or with emulsion stability.

Application examples

  • Dynamic surface tension of surfactant-carrying solutions, oils and highly viscous liquids
  • Emulsifier screening
  • Dispersions like paint, lacquers and foodstuffs
  • Adsorption kinetics of “moderately faster” surfactants
  • Determining concentration with medium surfactant content
  • Aging effects of oils, especially with insulating oils
  • Wetting agent concentration of galvanic solutions


LAUDA Measuring Instruments brochureDownload a PDF
of our Measuring Instruments brochure:

LAUDA Measuring Instruments Brochure (8.2 MB)

  The TVT advantages Your benefits
  • Drop volume method for precise measurement of surface and interfacial tension
  • Measurement range: 100 to 0.1 mN/m
  • Flexible device for a variety of applications
  • Characterization of multiple emulsifiers, for which the ring/plate technology cannot be used
  • Dynamic surface and interfacial tension depending on the drop age across a wide range
  • Quick overview of adsorption behavior of amphiphilic molecules on surfaces and interfaces
  • Extremely robust and controlled via intuitive Windows software
  • Temperature control with LAUDA thermostats
  • Can also be operated by untrained staff
  • No particular requirements of setup area
  • Automatic recording of temperature independence
  • Different views of the measurement curves and fitting of polynomial functions for analyzing the measurement data
  • Physically founded extrapolations beyond the measurement range to compare with other methods
  • Various syringes and needle combinations
  • Special needles for rising drops or glass needles
  • Easy replacement and cleaning
  • Flexible and fast switching between applications
  • Optimization of the measurement process
  • Particle-holding and critical samples also measurable, e.g. crude oils and strong acids.
  • Insensitive measuring element, no annealing necessary
  • Gas-proof closing of the system
  • Liquid-thermostated measuring cell and dosing syringe
  • Safe measurements of volatile and/or toxic substances
  • Exact thermostating at the measuring cell using LAUDA thermostats

TVT 2 Drop volume tensiometer

Drop by drop, the LAUDA TVT 2 measures the very small dynamic interfacial tension just as precisely as it does the surface tension of highly viscous samples. Individual drop measurements of up to 100 drops are possible. Time-critical functions, like drop monitoring and speed check, can be transferred from the PC to a powerful micro-processor. The TVT 2 consists of a measuring console and control panel. The core of the electronic part is made up of a micro-processor for controlling the discharge speed, the counting of the encoder pulses, and communications. LEDs and pictograms show the current status of the unit. The measuring console includes the easy-to-replace, temperature-adjustable syringe, the light sensor, a high-resolution travel sensor, and the precision mechanics for drop formation.

Lauda TVT 2

Included accessories:
Software · syringe 2.5 ml · standard needle 1.38 mm · glass cell · thermostating block · cell handling tool · plastic case

Additional accessories:
Syringes · needles · temperature-stable glass cells · reverse measuring set · temperature probe · thermostats

Special features

  • Positioning accuracy in the micro-meter range
  • Variable control of the feed rate by a factor of 300 using a Phase-Locked Loop (PLL) speed controller
  • Automatic adaptation of the light sensor‘s intensity to the used liquids
  • Quasi-static mode for very high surface ages
  • Simple connection to LAUDA thermostats for thermostating and software-controlled recording of the temperature dependency
  • Less than 1 ml sample necessary to record a measuring curve

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TVT 2 Drop volume tensiometer

Technical features TVT 2
   
Measurement range mN/m 0.1…100
Resolution
    Stroke µm ± 0.1
    Volume µl ± 0.01
    Surface/Interfacial tension mN/m ± 0.01
    Drop formation time s ± 0.1
Absolute precision Approx. 0.5 % of the end value of the surface tension
Drop times s/µl 0.04 (at 5 ml); 170 (at up to 0.25 ml)
Speed control <1 %
Temperature range °C 5…90
Interfaces RS 232
Dimensions TVT 2 Measuring console (WxDxH) mm 220x240x555
Dimensions TVT 2 Controller (WxDxH) mm 340x270x105
Weight TVT 2 Measuring console kg 8.0
Weight TVT 2 Controller kg 4.2
Power consumption W 0.5
Cat. No. 80…230 V; 50/60 Hz LMT 833 and LMT 935
 

Summary

Syringes

Cat. No. Description
EGP 009 Syringe, 250 μl
EGP 010 Syringe, 500 μl
EGP 006 Syringe, 1 ml
EGP 007 Syringe, 2,5 ml (included in LMT 935)
EGP 008 Syringe, 5 ml

Cuvettes

Cat. No. Description
EGG 011 Cuvette, standard (included in LMT 833)
EGG 013 Cuvette, increased stability against thermal shock
UD 329 Cell handling tool (included in LMT 833) EGG 011

Needles

Cat. No. Description
EGZ 005 Standard needle SK 1, 1.38 mm
EGZ 004 Standard needle SK 2, 1.05 mm
EGZ 006 Standard needle SK 3, 1.70 mm
EGZ 007 Standard needle SK 4, 0.63 mm
HX 453 Standard needle SK 5, 1.50 mm glass

Reverse measuring set

Cat. No. Description
LMTZ 908 Reverse measuring set consisting of:
HX 410 Needle adapter
HX 381 Reverse needle UK 1, 1.38 mm A
HX 380 Reverse needle UK 2, 1.05 mm A
HX 382 Reverse needle UK 3,1.70 mm A
HX 441 Reverse needle UK 4, 0.63 mm A

Thermostating and temperature control

Cat. No. Description
LCK 1910 ECO cooling thermostat RE 415 S*, 230 V; 50 Hz**
LRZ 913 RS 232/485 plug-in for temperature control
LRZ 918 External Pt100 plug-in
US 055 Temperature probe for measuring cell

* When not using the temperature probe or temperature control, other thermostats can also be used.
** Other power supply variants on request