Most detectorists struggle with their discrimination settings, often missing good targets or digging too much trash. The discrimination scale is your metal detector's way of categorizing targets by electrical conductivity - and understanding it properly can transform your hunting success.
A metal detector discrimination scale segments the range of metals by their conductivity, normally from low conductivity through to high conductivity. The range and number of segments in the scale can determine the accuracy and precision of target identification. The number of segments also determines the accuracy and precision of the Notch filter discrimination.
How Metal Detector Discrimination Works
Your detector sends electromagnetic pulses into the ground and measures how different metals respond. Highly conductive metals like silver and copper create strong, lasting signals. Less conductive metals like iron and foil produce weaker, shorter signals.
The discrimination circuit analyzes these signal characteristics and assigns each target a number on the conductivity scale. Most modern detectors use scales from 0-99, though some manufacturers use different ranges.
Common Conductivity Ranges by Metal Type
- Iron/Steel (0-20): Nails, bottle caps, iron relics
- Foil/Pull-tabs (20-40): Aluminum trash, some small gold jewelry
- Nickels (40-50): 5-cent coins, some costume jewelry
- Zinc/Copper pennies (50-70): Modern and wheat pennies
- Silver coins (70-90): Dimes, quarters, half dollars
- Large copper/silver (85-99): Silver dollars, large silver items
Understanding Discrimination Scale Accuracy
Higher segment counts don't automatically mean better performance. A 50-segment scale might give you more precise readings than a 20-segment scale, but other factors matter more:
Ground conditions affect accuracy. Mineralized soil, saltwater beaches, and trashy areas can shift target ID numbers. That silver quarter reading "82" in your test garden might show up as "75" or "88" at the beach.
Target depth changes conductivity readings. Deeper targets often read lower on the scale than shallow ones. A surface penny might hit "65," while the same penny at 8 inches reads "58."
Target size and shape matter. Thin items like chains or small earrings can read much lower than their metal type suggests. Large iron objects sometimes read higher, mimicking good targets.
Mastering Notch Discrimination Settings
Notch discrimination lets you accept or reject specific ranges on the conductivity scale. This feature works best when you understand what you're likely to find in different hunting scenarios.
Beach and Saltwater Settings
Salt water creates challenging conditions that affect discrimination accuracy. Many successful underwater metal detector users run with minimal discrimination to avoid missing good targets.
Try notching out only the lowest iron range (0-15) and digging everything else. Salt can make silver coins read like pull-tabs, so aggressive discrimination often backfires.
Park and School Ground Strategies
These sites typically have modern trash mixed with coins. Set your notch to reject pull-tabs (25-35) while accepting nickels (40-50) and higher conductors.
Many park hunters also notch out zinc pennies (50-60) to focus on silver coins and older copper pennies that read higher.
Old Homestead and Relic Hunting
Historical sites require different approaches. Iron relics can be valuable, so many relic hunters run with minimal discrimination or use iron audio to hear everything.
Consider running wide open initially, then gradually notch out obvious junk patterns as you learn the site's trash signature.
Advanced Discrimination Techniques
Use multiple sweep angles. Sweep over questionable targets from different directions. Trash often changes its conductivity reading dramatically, while good targets stay more consistent.
Pay attention to audio quality. Even if a target reads in the "good" range, scratchy or broken audio often indicates trash. Clean, solid tones usually mean solid targets.
Learn your detector's language. Spend time with test targets in different soil conditions. Your specific detector might read coins slightly higher or lower than the general ranges listed above.
Choosing the Right Metal Detector for Discrimination
Different detectors excel in different discrimination scenarios. Minelab metal detectors often feature sophisticated target ID systems with multiple tone options.
For beginners learning discrimination, beginner metal detectors with simple, proven discrimination circuits can be easier to master than complex multi-frequency units.
Treasure and relic metal detectors typically offer more sophisticated discrimination options for experienced hunters who need precise target separation in trashy sites.
Common Discrimination Mistakes to Avoid
Over-discriminating in unknown areas. Start with minimal discrimination and gradually add notch filters as you learn what trash is common.
Trusting target ID numbers completely. Always consider the full target signature: audio quality, signal strength, and how consistent the reading stays across multiple sweeps.
Ignoring ground balance effects. Poor ground balance can throw off discrimination accuracy. Properly balanced detectors give more reliable target ID readings.
Forgetting about target masking. In trashy areas, good targets can hide near junk and read incorrectly. Consider using smaller coils or metal detector accessories designed for trashy conditions.
Getting the Most from Your Discrimination Scale
The best discrimination strategy adapts to your hunting situation. Beach hunters need different settings than park hunters, and relic hunters need different approaches than coin shooters.
Practice with known targets in various conditions. Bury coins, jewelry, and common trash items at different depths and soil types. Learn how your detector responds before heading to new hunting grounds.
Consider investing in quality metal detector parts & accessories like pinpointers to help verify discrimination decisions and speed up target recovery.
Remember that discrimination is a tool, not a guarantee. Even the most sophisticated systems can be fooled by unusual targets, harsh ground conditions, or clever trash that mimics good finds. When in doubt, dig it out - you might be surprised by what you discover.
