Hello, so I got an advice to use shielded cable for dht and some other modules. I was searching how to connect it but i still dont know. So dht for example has gnd, 5V and signal. Should I connrct all 3 in same "cable" so all 3 are together in one "shield" and to where should I conect that shield.
Thank you very much for help!
Shield connected to 0v at one end only
All those cores together should be ok .
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If you have 3 wires and 1 shield wire, connect the shield on one side only (Arduino side) to earth GND.
Your sensor might need a pull up resistor on the signal pin.
- How long is this cable ?
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So I have cable with 3 wires in it and arount these 3 wires is this shield..
Earth gnd is gnd from arduino or gnd from mains?
It probably will be about 0.5m long maybe 1m
Earth GND is the GND found in an AC outlet.
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When the Arduino is connected to a PC USB cable, the Arduino GND is connected to earth inside the PC.
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At only 0.5 to 1 meter, suggest you forget about connecting the shield to anything.
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Thank you!
I've seen this advice "often", but I don't think I've ever seen it implemented in equipment, and I don't quite understand the rationale. Isn't any theoretical benefit pretty much negated if "ground" is also one of the "signals"? (I can't imagine the average RCS or 1/4inch audio cable working if GND is only connected on one side. Does it only really apply to, say, differential signals?)
I think a DHT would be more helped by a 10uF cap between GND and VCC, connected near the sensor...
Only if your PC is connected to mains. Not the case if using a laptop running on batteries - a lesson I learned the hard way.
On very long run cables, any current flowing in the shield when earth grounded at both ends (ground loop potential due to difference) can result in huge interference in the internal wires.
I’ve seen this many times in the field, usually at cable lengths over 10 meters.
Sometimes intermittent and a hell of a thing to track down if you aren’t aware.
Obviously.
Don't confuse a data ground with a shield being grounded. A shield is not a shield if it is also a conductor.
Edit: I should have written "data common" rather than data ground.
But for most digital circuits, Earth ground and circuit ground are connected, aren't they? How is ground loop current in the signal ground any better than in the shield?
At one end that goes to earth ground. 
If not earth ground, then your DC 0v.
Shield ground loop current (if shield is connected to earth at both ends) is due to induction from other current carrying cables in the same cable tray (same vicinity).
Also if there is an earth ground potential difference between the two ends, this results in earth ground current flow; I’ve seen earth ground potential differences of 30+ volts (cabling was about 300 meters in length).
Grounded on one end, no loop current induction.
When grounded at one end, static and spikes are shunted to earth, plus any cross over to other wires in that cable is common mode.
Obviously, the main ground end, not the sensor.
Yes, usually.
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