noob & English languge question - terminology :)

Discussion in 'General Electronics Chat' started by russian, Sep 28, 2012.

  1. russian

    Thread Starter Member

    Sep 1, 2012
    55
    1
    My question is partially about basic DC electronics terminology and partially about proper usage of English language while describing some schematic, hope this would be acceptable here.

    1) is 'low signal' synonym of 'ground'? Both are zero voltage, but are these terms interchangeable?

    2) what do you do - what would be the best verb - if you establish connectivity between something and ground? For instance, what is the proper way to say:

    "S3 sensor provides continuity between black/brown and red/white wires if door is closed, and disconnect between these wires door is even partially opened. This continuity applies ground to pin 16 of IC_501 which causes pin 8 of this chip to go low. If pedal is open, pin 8 of IC_501 goes high (+v5)."
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,431
    3,360
    1) No, they are not interchangeable. Ground and zero voltage might be interchangeable sometimes but not all times.

    Low signal definitely is not interchangeable with ground or zero voltage.

    1. A signal might be AC + DC. A low signal might mean low AC but still DC.
    2. A signal might be a current. For example, in 4-20mA systems, 4mA could mean low signal.
    3. A signal might be a logic signal. In RS-485 systems, a low signal could be a low voltage or high voltage depending which line you are looking at (A or B) or +D or -D on a USB interface.
    4. In some logic systems, a low signal might mean -800mV or some other level.

    2) When the door is closed, S3 sensor connects the black/brown and red/white wires.

    This grounds pin 16 of IC_501 which causes pin 8 of this chip to go low. If the pedal is open, pin 8 of IC_501 goes high."

    (In this context, using low to refer to zero volts or ground is clearly understood and acceptable. A reader knowledgeable in digital logic understands the meaning of low and high.)


    btw, your English is very good.
     
  3. Papabravo

    Expert

    Feb 24, 2006
    10,137
    1,786
    For a typical TTL part "low" is any voltage between GND and 0.8 Volts. A logic "high" is any voltage greater than 2.0 volts. In between is no mans land -- neither "high" nor "low"
     
    Last edited: Sep 29, 2012
  4. russian

    Thread Starter Member

    Sep 1, 2012
    55
    1
    Thank you guys, this helps a lot!
     
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