This article explains why are the monitor’s input power dimensions differ from the adapter’s connector size.

Short answer: They’re measured from different sides of the connection (jack vs. plug) and use different reference points. The monitor jack lists its center pin and entrance bore, while the adapter lists the plug’s inner hole and outer barrel. They’re designed to fit together.

Overview

• Example (Elo 1504L):
  • Monitor spec: “DC Jack (2.0mm pin outer diameter, 6.4mm barrel inner diameter)”
  • Power adapter plug: “5.5 mm outer barrel × 2.1 mm inner hole”
• This difference is normal and intentional. The parts are designed to mate securely.

How the measurements map

• Jack (on the monitor):
  • 2.0 mm = diameter of the jack’s center pin
  • 6.4 mm = diameter of the entrance bore/collar (a guide, not the contact)
• Plug (on the adapter):
  • 5.5 mm = outer diameter (OD) of the plug’s barrel
  • 2.1 mm = inner diameter (ID) of the plug’s hole

Center pin: 2.0 mm vs. 2.1 mm

• The jack’s center pin is 2.0 mm (monitor side).
• The plug’s inner hole is 2.1 mm (adapter side).
• That 0.1 mm difference is intentional clearance so the plug slides on easily while the jack’s spring contacts maintain proper pressure for a reliable electrical connection.

“6.4 mm barrel inner diameter” (jack side)

• The 6.4 mm value is the jack’s front bore/entrance, not the electrical contact size.
• Inside the jack, spring contacts are sized to grip a 5.5 mm plug barrel.
• The larger 6.4 mm bore provides insertion clearance and tolerance so the 5.5 mm plug seats fully and consistently.

Compatibility summary

• Even though the numbers differ, the supplied 5.5 mm × 2.1 mm adapter plug is fully compatible with a 2.0 mm pin jack and a 6.4 mm entrance bore. This pairing is standard and provides a secure, correct power connection.

Best-practice checks

• Always verify voltage, current rating, and polarity (typically center-positive) match the monitor’s requirements before use.

Visual reference

• See the photos/diagram below for a color-coded cross‑section showing:
  • 5.5 mm plug barrel (contacted by jack springs)
  • 2.1 mm plug inner hole over a ~2.0 mm jack pin (intentional clearance)
  • 6.4 mm jack entrance bore (non-contact guide)