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Hub Port-to-Port etc. Resistance Checks

(see also USB Hub and PSU Cable Resistance Checks)

Measurements

Model
(Powered|Unpowered)

Input-to-Port
±0.05 Ω1

Port-to-Port
±0.05 Ω1

Power-to-Input2
±0.05 Ω3

Isolation
Confirmed?
4

Old 4-Port Hub5 (P)

NC6

0.1

NC6

OEM 4-Port Hub (P)

NC6

<0.05

NC6

thumbs-up.png

CLIPtec Combi-Hub & Card Reader (P)

Diode-like7

<0.05

Diode-like7

thumbs-up.png

"Flower" 4-Port Hub (U)

1.3

0.1

N/A8

Gembird 4-Port Switching Hub (P)

Diode-like9

<0.05

thumbs-up.png

Generic 4-Port Hub (EDO) (P)

0.2

<0.05

0.3

alert.png

Generic 4-Port Hub (Sum Vision) (U)

13.3

2.5

N/A8

Hama 4-Port Hub (P)

NC6

<0.05

NC6

thumbs-up.png

PowerSynch Tech. 3-port Hub & LAN adapter (P)

<0.05

<0.05

0.1

alert.png

Pluscom 3-port Hub & Card Reader

0.1

<0.05

0.1

alert.png

Pluscom UHBPC 4-port Hub (U)

1.3

0.2

N/A8

Pluscom UTO 4-port Hub (P)

0.3

0.1

0.3

alert.png

Sweex 4-Port Hub (P)

0.2

<0.05

0.1

alert.png

Targus "Cable-powered" 4-Port Hub (P)

Diode-like10

<0.05

Diode-like11

thumbs-up.png

Trust 3-Port + Camera "Port" Hub (U)

0.2

<0.05

N/A8

Trust 4-Port Netbook Hub (U)

0.3

<0.05

N/A8

USB Now 4-Port Hub (P)

0.3

<0.05

0.4

alert.png

Conceptronic 4-Port, Cube Hub (P)

NC12

0.15

Diode-like

Generic 7-Port Hub13 - Front Ports (P)

0.1

<0.05

0.4

alert.png

Generic 7-Port Hub13 - Rear Ports (P)

1.0

0.4

Generic 7-Port Hub13 - Front to Rear Port (P)

N/A8

0.3

2-port USB KVM Switch

Diode-like14

<0.05

N/A8

Power Isolation Cross-check

DSCN0993cs.jpg

DSCN0994cs.jpg

Isolating and "Back-power" Indicating Adapter

The adapter(s) above were used to cross-check power-to-input isolation where expected, or not, for some of the powered hubs. Column four has either thumbs-up.png when isolation was confirmed (LED not illuminated when a PSU connected to the hub) or alert.png when "back-powering" was possible (LED illuminated when a PSU connected to the hub). Whilst "back-powering" a Pi is reasonable if a single PSU is used to power both the Pi and the hub15, good isolation is necessary when separate (and similar) PSU's (one for the Pi, another for the hub) are used. The veroboard adapter part also includes a "track-break" to provide the necessary isolation of "back-powering" hubs for test purposes.

See also USB Hub ID's etc. List.


  1. Allowing for a total connected cable resistance of 0.6 ±0.05 Ω (1 2)

  2. Connection required if "back-powering" a Raspberry Pi (3)

  3. Allowing for a total connected cable resistance of 0.3 ±0.05 Ω (4)

  4. Powered Hubs Only (5)

  5. Partially Working (6)

  6. No measurable Connection (>200 Ω) (7 8 9 10 11 12)

  7. >2000 | ~1980 Ω (13 14)

  8. Not Applicable (15 16 17 18 19 20 21)

  9. >200 | ~180 Ω (22)

  10. >200 | ~174 Ω (23)

  11. >200 | ~171 Ω (24)

  12. No measurable Connection (~100 kΩ) (25)

  13. 2 x 4-Port Hubs in series (26 27 28)

  14. >200 | ~193 Ω (29)

  15. With Caution, since the Pi's PSU protection circuitry is bypassed (30)


2019-11-22 15:19