Master The Diamond Selector 2: Step-by-Step Calibration And Operation Guide

Operating the Diamond Selector II requires setting the meter sensitivity dial based on ambient room temperature and stone carat weight, allowing the copper thermal probe to warm up until the READY lamp illuminates. Hold the tester with your finger touching the rear electrical conductive plate and place the spring-loaded probe perpendicular to a clean stone facet at a 90-degree angle. Real diamonds rapidly transfer heat, triggering a continuous audio tone and lighting up the red LED scale to level 9 or higher, while simulants like glass or cubic zirconia produce no thermal dissipation response.

Pre-Testing Setup and Calibration Requirements

Before testing any gemstone, you must establish controlled environmental conditions and inspect the device hardware. The Diamond Selector II relies on micro-thermal conductivity differential analysis. Because ambient room temperature directly alters the baseline thermal resistance of the copper probe, skipped calibration leads directly to false readings.

• Essential Equipment & Tools:
  
  
  • Diamond Selector II unit with protective probe cap.
  • Fresh 9-Volt alkaline battery (6F22 or NEDA 1604 type).
  • Loose stone testing tray (loose metal disc with cutout wells for unmounted stones).
  • Microfiber lint-free cloth and 99% isopropyl alcohol.
  • Precision jeweler's tweezers.
• Mandatory Standards & Knowledge:
  
  
  • Awareness of ambient testing temperature within a 10°C to 35°C (50°F to 95°F) window.
  • Approximate carat weight estimation of the subject stone (less than 0.05 ct, 0.06 ct to 0.50 ct, or greater than 0.50 ct).
  • Understanding that thermal probes test thermal dissipation rates, not optical refractive indexes.
• Operating Benchmarks:
  
  
  • Device warm-up duration: 20 to 30 seconds.
  • Testing time per stone: 1 to 2 seconds.
  • Target voltage requirement: Minimum 7.5V stable DC power output.

Step-by-Step Guide to Operating the Diamond Selector II

Step 1: Battery Installation and Thermal Preheat Phase

Remove the rear battery compartment cover on the back of the Diamond Selector II. Connect a fresh 9-volt alkaline battery to the terminal clip, ensuring polarity matches the internal housing diagram. Replace the cover securely.

Turn the power/volume dial located on the right side of the unit clockwise past the click threshold. The red POWER indicator light will turn on immediately, signaling that current is flowing to the internal heating element. Allow the unit to sit undisturbed for 20 to 30 seconds. Do not touch the probe tip during this phase. Once the internal thermistor reaches operational equilibrium, the green READY light on the front panel will illuminate.

Warning: Never attempt to test gemstones while the green READY light is unlit. Applying the probe during the warm-up cycle delivers invalid thermal conductivity readings and can cause thermal shock to delicate synthetic materials.

Step 2: Calibrating Sensitivity Against Temperature and Carat Weight

Locate the scale adjustment dial on the side of the unit and observe the LED meter panel numbered 1 through 9. The meter features three distinct color bands: yellow (levels 1–4), green (levels 5–8), and red (levels 9+).

Determine the current room temperature and the approximate weight of the stone. Adjust the side sensitivity dial until the LED light bar illuminates up to the target baseline start level specified by the manufacturer's thermal matrix. For example, at a standard room temperature of 20°C (68°F) testing a 0.25-carat stone, turn the volume dial until the green lights illuminate exactly up to level 3 on the scale.

Pro-Tip: Re-calibrate the baseline level whenever moving between environments, such as transferring from an air-conditioned showroom to an outdoor estate auction site, as a 5°C shift alters thermal dissipation thresholds.

Step 3: Gemstone Cleaning and Surface Preparation

Thermal testing requires direct, uninhibited contact between the solid copper probe tip and the atomic lattice of the gemstone. Surface oil, dirt, cosmetics, or fingerprint grease act as thermal insulation layers, preventing accurate heat transfer to the probe's internal thermistor.

Dip a lint-free microfiber cloth in 99% isopropyl alcohol and scrub the table facet and crown of the gemstone thoroughly. Allow the stone to air dry for 10 seconds. If the stone is unmounted, place it into the appropriate recessed hole of the metallic testing tray provided with your kit. Never hold loose stones in your fingers or on plastic surfaces during testing, as human body heat alters the baseline temperature of the gemstone.

Step 4: Probing Protocol and Electrical Conductive Contact

Hold the Diamond Selector II in your dominant hand. Position your index finger and thumb to make firm, direct skin contact with the metal conductive panel located on the rear casing of the device. This contact completes the grounding circuit necessary for the internal sensor system to evaluate heat dissipation accurately.

Uncover the protective cap over the needle-thin copper probe. Hold the unit perpendicular to the facet of the gemstone, forming a precise 90-degree angle with the surface being tested. Gently press the probe tip against the flat facet until the spring-loaded probe retracts slightly into the housing sleeve. Apply only minimal downward pressure—just enough to depress the internal spring mechanism by 0.5 millimeters.

Warning: Do not apply sideways pressure, slip across the facet edge, or push down hard on the probe tip. Bending the micro-copper pin destroys calibration accuracy and can permanently snap the delicate internal heating sensor.

Step 5: Interpreting Audio-Visual Signals and Thermal Indicators

Maintain contact between the probe tip and the stone facet for 1 to 2 seconds while reading the illuminated LED display panel:

1. Diamond Confirmation: The light bar rapidly climbs from your calibrated baseline level straight into the upper red zone (levels 9, 10, or higher), accompanied by a continuous, high-pitched acoustic beep tone. This rapid thermal drain confirms high thermal conductivity unique to diamond structures.
2. Simulant/Glass Signal: The light bar remains static at the calibrated baseline level (yellow/green zone) or drops downward. No acoustic beep sounds. Materials such as cubic zirconia, glass, synthetic spinel, and YAG dissipate heat too slowly to trigger the sensor.
3. Metal Contact Alert: If the probe slips off the gemstone and touches the gold, platinum, or silver setting, the unit outputs a rapid, intermittent buzzing sound alongside a maximum LED flash. Retract the probe instantly, re-align perpendicular to the stone facet, and re-test.

Thermal Calibration and Sensitivity Matrix

Use this reference table to set the correct starting meter light level on your Diamond Selector II based on ambient testing room temperature and estimated target carat weight.

Troubleshooting Operational Anomalies and False Readings

Instant Max Beeping When Testing Small Mounted Stones

• Root Cause: The probe tip is physically bridging across the tiny stone facet and touching the adjacent metal prong or bezel mounting. Metal has extremely high electrical and thermal transfer rates, triggering the metal warning system.
• Actionable Fix: Use a bench loupe under high magnification while placing the probe tip. Re-orient the probe perpendicular to the table facet, far away from setting prongs. If testing stones under 0.02 carats mounted in tight pave settings, use a micro-probe tester specifically designed for micro-pave mounts.

No LED Movement on a Known Diamond Sample

• Root Cause: The 9-volt battery voltage has dropped below 7.5V operational threshold, or your skin is not making direct contact with the rear conductive metal plate on the back of the tester housing.
• Actionable Fix: Replace the internal 9V battery with a brand-new high-drain alkaline unit. Inspect the metal contact plate on the back of the device; clean off any tarnish or dirt, and ensure your hand touches the metal plate directly while probing.

Positive Red Light Result on Synthetic Moissanite

• Root Cause: The Diamond Selector II is strictly a thermal conductivity tester. Synthetic Moissanite (Silicon Carbide) possesses a thermal conductivity profile almost identical to natural diamond, causing thermal-only probes to read moissanite as a genuine diamond.
• Actionable Fix: Cross-test any thermally positive stone with a dedicated electrical conductivity meter (such as a Moissanite Tester or Dual Multi-Tester). Moissanite conducts electricity, whereas natural type IIa/Ia diamonds do not (with the exception of rare blue type IIb diamonds).

Fluctuation or Intermittent Beeping During Probe Contact

• Root Cause: Inconsistent hand pressure causing the spring-loaded probe tip to bounce against the facet, or heavy body oils insulating the contact point.
• Actionable Fix: Clean the stone using 99% isopropyl alcohol. Rest your probing hand's wrist flat on your work surface to stabilize your hand movement, and apply smooth, continuous, perpendicular pressure for 2 full seconds without tilting the unit.

Frequently Asked Questions

Can the Diamond Selector 2 tell the difference between diamond and moissanite?

No. The Diamond Selector II tests thermal conductivity only, and because synthetic moissanite shares an almost identical thermal transfer rate with diamond, it will produce a positive red-light reading. To separate moissanite from diamond, you must follow up with an electrical conductivity tester or use a loupe to inspect for double refraction facet doubling.

Why does the Diamond Selector II buzz loudly when touching metal settings?

The loud buzzing sound is an automated metal-detecting safety feature designed to warn the operator that the tip has slipped off the gem facet onto a gold, silver, or platinum setting. Metal contact completes the grounding circuit instantly; retract the probe tip immediately to avoid false positive readings.

How do I know when to replace the battery in my Diamond Selector II?

Replace the 9-volt battery when the green READY light takes longer than 60 seconds to turn on, if the LED meter dims noticeably during testing, or if the unit fails to hold calibration stability. Maintaining a stable 9-volt input voltage ensures accurate thermal probe heating and signal readings.

Does the Diamond Selector 2 work on lab-grown diamonds?

Yes. Lab-grown diamonds (both CVD and HPHT) possess identical chemical composition, crystal structures, and thermal conductivity properties as mined natural diamonds. Consequently, the Diamond Selector II correctly registers lab-grown diamonds in the upper red LED zone with a continuous beep tone.

Elevate Your Gemological Testing Precision

Integrating thermal conductivity tools like the Diamond Selector II into your appraisal workflow requires reliable equipment and strict testing protocols. Pair your thermal testing workflow with high-grade optical loupes and electrical moissanite detectors to build an unassailable, multi-layered gemstone verification protocol.