manufacturer :       Micromeritics

model :                   Gemini 2375

annotation :           Dokumente engl.

Attention: This is description for Gemini II 2370. The Models are identical.

The Gemini Analyzer is an easy to use, fully automatic, single- or multi­point surface area analyzer. Once an analysis is started, data are collected, cal­culations performed, and results displayed without further Operator intervention. The frequent calibrations associated with presently available flow­ing-gas systems are not required. The analyzer may be operated in any of live languages: English, French, German, Italian, or Spanish.

Gemini provides rapid and accurate sample analysis, including selectable cal­culation of the following sample characteristics:

n          Single-point BET surface area

n          Multi-point BET surface area

n          Multi-point Langmuir surface area

n          t-Method micropore volume and area

n          Total pure volume

As nue as 50 data points can be collected and reported in the BET, Lang­muir, or t-Method range. Additionally, Gemini can report discrete point ad­sorption isotherms consisting of up to 1,000 adsorption points.

Up to ten Run Conditions Sets (Setup Groups) can be stored, enabling you to perform custom analyses with just a few keystrokes.

Analysis results can also be edited by specifying which points are to be included in surface area or t-Method calculations. Gemini automatically recal­culates the results and generates a new report. Reports remain available for viewing or printing until anotheianalysis is started. Results can also be trans­mitted to a remote location or computer via the standard RS-232 connector.

The Gemini Analyzer, shown in the following Illustration, contains a sample station and an attached keypad and display. The analyzer is controlled by commands entered through the keypad. The operational status of the analyzer can be continually monitored an the display.

The primary function of the Gemini is to deterrnine the surface area of solid materials. lt uses a flowing-gas technique in which the analysis gas flows into a tube containing the sample and into a balance tube, at the same time. The internal volume and the temperature surrounding both tubes are main­tained at identical conditions. The only difference is the presence of the sample in the sample tube.

The sample and balance tubes are immersed in a single liquid nitrogen bath which maintains isothermal conditions for both tubes. The analysis gas is then delivered•to the sample tube by a servo valve mechanism. The delivery rate of analysis gas flow into the balance tube is controlled by another servo valve connected to a differential pressure transducer. This differential pressure transducer measures the pressure imbalance between the sample and balance tubes, which is caused by the adsorption of the analysis gas onto the sample. As the sample adsorbs analysis gas, the pressure drops in the sample tube. The servo valve continuously restores the pressure balance between two tubes by admitting more gas into the sample tube. The end result is that the Gern­ini maintains a constant pressure of analysis gas over the sample while vary­ing the rate of analysis gas delivery to exactly match the rate at which the sample can adsorb the gas.

APPLICABILITY

Surface Area:                       0.1 m ² to above 300 m ² , total;

                                            0.01 m ² /g and higher, specific

Pore Volume:                       4 x 10 ^-6 cm ³ /g and higher

PRESSURE MEASUREMENT

Range:                                 0 to 950 mmHg

Minimum Resolvable

Relative Pressure (P/Po):    10 ^-4

Pressure Resolution:           0.1 mmHg

Accuracy and Linearity:       Better than ±0.5%

(Transducer manufacturer's

specification )

VACUUM SYSTEM

External:                               Vacuum source achieving better than 20 x 10 ^-3 mmHg at the instrument inlet, and having a device to reduce oil vapor backstrearning is recommended.

The system should also have an anti­suckback valve to prevent oil from being admitted into the Gemini should there be a power failure.

ENVIRONMENT

Temperature:                       10 to 35 °C (50 to 96 °F) operating

                                            0 to 50 °C (32 to 122 °F) non-operating

Humidity:                              20% to 80% relative, non-condensing

SAMPLE TUBES

Standard Tube:                    The standard tobe has a 0.95-cm (3/8-in.)

outside diameter and is 15.5 cm (6.1 in.) long with 6.5 cm ³ of volume. Sample capacity is approximately 2.0 cm ³ .

Large Tube:                          The bulb of the large tube has a 1.9-cm

(3/4-in.) outside diameter and is 3.8 cm (1-1/2 in.) long. The tube is 15.5 cm (6.1 in.) long. Tt yields a 12.0-cm ³ volume. Sample capacity is approximately 6.0 cm ³ .

ELECTRJCAL

Voltage:                                85 to 264 VAC

Frequency:                           47 to 440 Hz

Power:                                  75 VA maximum

GASES

Adsorbate

Optimized for nitrogen in a liquid nitrogen sample bath. Gemini may be used with non­ . corrosive adsorbate gases having vapor pressures at both room and bath temperatures that are acceptably high relative to the resblution of the 1,000 mmHg pressure transducer. Typically, oxygen, argon, carbon dioxide, butane, methane, and other light hydrocarbons will produce useful data above absolute

pressures of a few mmHg.

PHYSICAL

Height:                                52.4 cm (20.6 in.)

Width:                                 43.8 cm (17.3 in.)

Depth:                                30.5 cm (12.0 in.)

Weight:                               22 kg (48.4 lbs)