showstack

Unit load 單位負載

The standard reference load an RS-485 bus segment is rated against — one unit load is roughly a 12 kΩ receiver input. The spec caps a segment at 32 unit loads, but that is not the same as 32 devices: most modern DMX/RS-485 receiver chips present a fraction of a unit load (1/8 UL is common), so a real line can carry well over 32 physical fixtures before it needs an opto-splitter. Check the fixture manual for its actual unit-load figure rather than counting boxes.

中文

RS-485 匯流排的標準參考負載。DMX512 一段最多 32 個單位負載，但現代收發器多為 1/4 或 1/8 單位負載，實際可掛的設備數因此不同。

Next to this

Where it shows up on the wire

Sources

• TB511: The Unit Load Concept — Renesas Electronics primary
• The RS-485 Unit Load and Maximum Number of Bus Connections — Texas Instruments