Presidium Diamond Fact II Manual - iGem Instruments

Principle of Operation

The PRESIDIUM Diamond Fact II has been developed to distinguish between a diamond and its simulants. It makes use of the fact that a diamond conducts heat better than any known diamond simulant. Other properties of diamond, such as its high refractive index, can be closely matched by other materials and they are therefore less useful in identifying this most precious gemstone.

Heat Conductivity of Diamond and Some of its Simulants

The PRESIDIUM Diamond Fact II is based on an invention by Professor Julian Goldsmid of the University of New South Wales, Australia. The Heat Pen consists of two linked thermometers, one of which is heated electrically while the other is cooled by the gemstone being tested. The difference between the temperatures of the two thermometers is a measure of the heat conductivity of the gemstone and gives rise to an electrical output that is amplified and displayed on a meter. The meter reading thus indicates the heat conductivity.

Preparing the PRESIDIUM Diamond Fact II for Use

1. The two AA batteries fit into the battery compartment of the instrument (note + - symbols). Alkaline batteries should be used as they have a life of approximately 4 hours of continuous use. Ordinary batteries may be used but will give a shorter working life.
2. The heat pen should be linked to the meter unit by inserting the multi-pin plug at the end of the cable into its socket.
3. Turn on the switch and wait about 20 seconds which is the initial warm-up period. A small reading on the meter, above or below zero, at this stage is quite normal.
4. Press the tip of the heat pen on the simulant test disc located to the right of the meter window. Use as much pressure as is necessary to make the protruding tip retract completely into the end of the heat pen. Within two or three seconds the needle should reach its highest point well within the red band of the meter display.
5. Press the tip of the heat pen on the diamond test disc located to the right of the simulant test disc. Within two or three seconds the needle of the meter should reach its highest point well within the green band of the meter display.
6. Adjusting the meter. The PRESIDIUM Diamond Fact II has been completely calibrated during manufacture and no further adjustment should be needed, If recalibration should become necessary, the slotted screw in the recess indicated by CAL should be used. Turn the screw carefully with a screwdriver until the meter gives a reading just inside the top of the red portion of the meter when tested with the simulant disc. The reading should then be well into the green portion of the meter when tested with the diamond test disc.

How to Perform a Test

1. With the gemstone to be tested at room temperature, press the tip of the heat pen against a facet. Hold the pen at a slight angle in order to observe the contact of the tip with the facet and apply just enough pressure to make the exposed tip retract into the pen. Maintain a steady contact of the tip with the facet.
2. Observe the highest reading on the meter. The needle will rise rapidly, reach its highest value within two or three seconds and then fall slowly.
3. If the reading reaches the green band, a diamond is indicated and if it does not reach the green band, a simulant is indicated.
4. The PRESIDIUM Diamond Fact II can still be used when the batteries are nearing the end of their life, provided the indicator lamp still glows. If it does not glow brightly, it is best to replace the batteries.

Note: Presidium Diamond Fact II ( PDF II) is an improved version of the previous model Presidium Diamond Fact ( PDF ). The PDF II comes with the Auto - Thermal Control for the heat pen to provide more reliable reading and no waiting time is needed after each test. The PDF II is easy to recognize by its nameplate on the main unit marked with golden background PRESIDIUM DIAMOND FACT II and gold platted 6 pins probe pen plug.

Important Notes

1. The gemstone should appear to be clean and dry before testing but elaborate cleaning procedures are unnecessary.
2. Rather low readings in the green band must be expected with very small diamonds.
3. When a number of tests are being made, it is advisable to use the test discs from time to time to insure correct results.
4. Low readings, near the bottom of the red band, will be observed for glass and cubic zirconia and rather high readings, near the top of the red band, for sapphires.
5. The PRESIDIUM Diamond Fact II has been subjected to thorough and extensive laboratory tests and checks. It will give a clear and reliable indication of whether or not a particular gemstone is a diamond. Where any doubt exists, supporting tests should be performed.

Under no circumstances shall PRESIDIUM Instruments Pte Ltd, the manufacturer, or any of its distributors be liable for Direct or Indirect Damages Sustained in Connection with the PRESIDIUM Diamond Fact II.

Maintenance

1. The heat pen and particularly its tip should be handled carefully. Caution should be used when removing the protective cap so as not to damage the tip. When the heat pen is not in use, always replace the cap to protect the tip.
2. Change batteries as soon as the indicator lamp fails to glow brightly.
3. Do not leave dead batteries in the battery compartment as they may corrode and cause damage. Batteries should be removed when the PRESIDIUM Diamond Fact II is to be stored tor an extended period of time.