Firma:                TA Instruments

Modell:              AR 500

Kommentar:      Dokumente engl.

The TA Instruments AR Rheometers are fifth­generation instruments, which functions as either a controlled-stress or controlled-rate Instrument.

The rheometers are designed to fulfill the requirements of measurement as implied by the füll meaning of the term rheology—defined as the "study of the deformation and flow of matter."

Deformation is measured in the non-destructive region of elastic or visco-elastic deformation. This can give invaluable Information concerning the microscopic interactions in the test material, as well as measuring the shear stress/shear rate relationships at higher Stresses.

In the controlled-stress technique, the stress can be applied and released at will, and the actual behavior of the Sample can be measured directly. This is not usually possible wich conventional controlled-shear rate instruments. In addition, most real-life situations can be simulated more accurately using controlled-stress measurements.

Instrument Components

The Instrument consists of a main unit mounted on a cast metal stand, with the electronic control circuitry contained within a separate electronics control box. Figure 2.3 Shows the front and rear of the electronics control box.

The AR Rheometer contains an electronically­controlled induction motor with an air bearing Support for all the rotating parts. The drive motor is equipped with a hollow spindle, with a detachable draw rod inserted through it. The

draw rod has a screw-threaded section at the bottom, which allows the geometry to be securely attached.

The measurement of angular displacement is dope by an optical encoder deviee. This can detect very Small movements down to 0.6 prad. The encoder consists of a non-contacting light source and photo-cell, arranged either side of a transparent disc attached to the drive shaft. On the edge of this disc are extremely fine, accurate photographically-etched radial lines. Therefore, this is a diffraction grating. There is also a stationary Segment of a similar disc between the light source and encoder disc. The interaction of these two discs results in diffraction patterns that are detected by the photo cell. As the encoder disc moves when the sample strains under stress, these patterns change. The associated circuitry interpolates and digitizes the resulting Signal to produce digital data. This data is directly related to the angular deflection of the disc, and, therefore, the strain of the sample.

The main electronics are housed in a separate control box. The interplay between the rheometer/electronics and Controller are explained in more detail in Chapter 5.)

Temperature control is achieved in the Standard configuration via a Peltier plate System.

Technical Specifications

Dimesions

AR-N Instrument Section (Casting):

Width:            9 in. (22cm)

Height:           23,5 in. (60cm)

Depth:            10 in. (25 cm)

Weight:          48.5 lbs (22 kg)

AR-N Controller:

Width:            7,5 in (18.5 cm)

Height:           14,5 in. (37 cm)

Depth:            17 in. (43 cm)

Weight:          46,2 lbs (21 kg)

Supply Voltage          230 Vac 5 amps

                                 120 Vac 10 amps

Frequency                 50 to 60 Hz

Power                        800 Vac

Torque                       0.1 µNm to 100 mNm (AR 1000)

Range                       1µNm to 50mm (AR 500)

Shear Stress             0.0008 to 508,000 Pa (AR 1000)

Range (Geometry    0.008 to 254,000 Pa (AR 500)

Dependent)

Frequency                 0.1 mHz to 100 Hz (AR 1000)

Range                       (0.628 mrad s ^-1 to 628 rad s ^-1 )

                                 0.1 inHz to 40 Hz (AR 5 00)

Angular                      Controlled Stress:

Velocity                      10 ^-8 to 100 rad s ^-1

Range                       Controlled Strain:

                                 10 ^-2 to 100 rad s ^-1

Angular                      0.62 µrads

Displacement

Resolution

Shear Rate Range   10 ^-6 to 11,000 s ^-1

(Geometry, material

and technique

dependent.)

Minimum strain         0.00006

Normal force

Range:                      1 g to 5000 g

Peltier System Specifications

Peltier                        Standard: -10 °C to 99 °C

System                      Extended: -20 °C to 180 °C

Range

NOTE: Extended use of the extended Peltier plate is not recommended above 150 °C. Also, the lower temperature ramps can be significantly reduced by circulating an appropriate refrigerant.

Ramp Rate               20 °C min ^-1

(Standard)

(Typical)

Ramp Rate               (20 to 100 °C) 50 °C min ^-1

(Extended)                (100 to 150 °C) 25 °C min ^-1

Internal                      0.016 °C

Resolution

of Pt100

Optional Accessory Specifications for Extended Temperature Module (ETM)

ETM Temperature

Range                       -100 °C to 400 °C

Ramp Rate

(Typical)                    120 °C min ^-1

Internal

Resolution                 0.025 °C