Comparing Span Adjustment Techniques: Magnetic Pens versus Adjustment Pots
- Bob
- Sep 5
- 2 min read
Feature | 🔹 Magnetic Pen Style | 🔧 Adjustment Pot Style |
How It Works | Non-contact span change using a magnetic tool on sensor housing | Manual turning of a small trim screw (potentiometer) |
Adjustment Interface | Built-in reed switch or sensor detects magnetic field and steps through modes | Tiny screwdriver slot (pot) physically adjusts signal |
Common on | Smart/digital transducers, newer models | Older analog sensors, simple setups |
Pros and Cons for Maintenance Teams
Magnetic Pen Style
✅ Pros
No opening or disassembly required → safer and faster in dirty or hot environments.
No risk of contaminant ingress (no open holes).
Repeatable settings – often LED indicator shows span level.
Often tamper-resistant – only authorized tools trigger it.
⚠️ Cons
Can be confusing for new techs without training (hidden modes, time-sensitive steps).
Requires special magnetic pen – easy to lose.
No fine-tuning – some models only allow step adjustments (not continuous).
Electronic failure can prevent adjustments.
Adjustment Pot Style
✅ Pros
Simple and intuitive – turn to adjust.
Fine-grain control over span (ideal for precision tuning).
No special tools – just a small screwdriver.
Can often be adjusted live during pressure application.
⚠️ Cons
Requires opening a cover or accessing tight area.
Vulnerable to contamination or moisture intrusion.
Easier to over-adjust or damage if untrained hands turn too far.
No feedback (blind adjustment unless paired with readout).
Maintenance Preference Summary
Scenario | Recommended Style |
Dirty or wet environment | 🔹 Magnetic Pen |
Quick field adjustment needed | 🔧 Pot Style |
New or untrained technician | 🔧 Pot Style (simpler) |
Precision calibration required | 🔧 Pot Style |
Secure or tamper-proof needed | 🔹 Magnetic Pen |
Pro Tips ==>
Always verify calibration using a simulator or known pressure source.
Label transducers with their adjustment method to avoid confusion.
Keep a spare magnetic pen in a known location if using smart sensors.
For pot-style: Use a non-metallic screwdriver when possible to avoid shorts.
**Always check with your process management team for formal procedures. These are shared to for thought and examination of general procedures.
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