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  1. #1
    Join Date
    May 2002
    Location
    Baton Rouge, Louisiana
    Posts
    3,924
    Hey everyone, how bout we start a thread to help out new people and old, anything from straight and simple to generic.


    I saw someone post this already but

    on a 4 to 20ma device you can use a 250 ohm resistor to make the device 0 to 5 VDC or 500 ohm for 0 to 10 VDC

    Honeywell Modutrol Motors-Have a bunch of them that are potentiometer and you need a DC input instead? Honeywell makes a module that you can plug into the motor to change it to VDC, you can find the PDF on the module here
    http://hbctechlit.honeywell.com/tech...0s/63-2235.pdf

    Also Honeywell has the famous "Gray Book" you can find it here, its a big download
    http://68.209.216.66/html/Training/H...llTraining.htm
    Quote Originally Posted by MatrixTransform View Post
    very soon it is you that will be pwned

  2. #2
    Thanks for the links, good stuff.


  3. #3
    your grey book link is dead.

  4. #4
    Join Date
    May 2002
    Posts
    9,564
    Quote Originally Posted by sysint View Post
    This should just be a standard posting at the top of this section:
    HONEYWELL ENGINEERING MANUAL of AUTOMATIC CONTROL for COMMERCIAL BUILDINGS

    ....Otherwise known as the Honeywell Grey Manual.

  5. #5
    Join Date
    Mar 2005
    Location
    Virginia
    Posts
    1,144

  6. #6
    Join Date
    Aug 2006
    Location
    New England
    Posts
    520
    on a 4 to 20ma device you can use a 250 ohm resistor to make the device 0 to 5 VDC or 500 ohm for 0 to 10 VDC
    Just a slight correction: 250 ohms gets you 1-5VDC. 500 ohms gets you 2-10VDC. Good ole Ohm's Law: 500*.004=2 500*.02=10

  7. #7
    Join Date
    May 2002
    Location
    Baton Rouge, Louisiana
    Posts
    3,924
    Quote Originally Posted by ctrlguy View Post
    Just a slight correction: 250 ohms gets you 1-5VDC. 500 ohms gets you 2-10VDC. Good ole Ohm's Law: 500*.004=2 500*.02=10
    It was 2 years ago, you can give me a break on the math

    Also the Honeywell book in book form

    http://store.hydronicpros.com/product.php?qcp=1028

  8. #8
    Join Date
    Jul 2002
    Posts
    908
    Why'd ya leave out the 1000ohm? That converts ma to volts directly. I've used AOs as constant DC sources before.

  9. #9
    in control, please explain about the 1000 Ohm set-up.

  10. #10
    Join Date
    Mar 2005
    Location
    Virginia
    Posts
    1,144
    1000ohm will turn 0-20ma to 0-20vdc
    500ohm will turn 0-20ma to 0-10vdc
    375ohm will turn 0-20ma to 0-7.5vdc
    250ohm will turn 0-20ma to 0-5vdc
    etc....
    Use the formula (V = I x R)

    Some controllers have a max load of 500ohms, etc... So you cant do this with everything.


    Edit: almost forgot about this site -
    http://www.csgnetwork.com/ohmslaw.html

    Use the "To calculate the circuit voltage" (V = I x R)

    So on the webpage, in the Amps field put .004 (4ma), put 500 in the Ohms field, click calculate and you get 2 volts,
    etc...
    Last edited by codewriter; 02-10-2007 at 05:12 PM.

  11. #11

    transmitters and transducers?

    basic question------------what is the difference between a transmitter and a transducer?

  12. #12
    Join Date
    Dec 2006
    Location
    Hartford, Connecticut
    Posts
    442
    A Transmitter would be a Field Device connected to a DDC Controller as an Analog Input Point, such as a static pressure transmitter or %RH.

    A Transducer is connected to a DDC Controller on a Analog Output Point, which would modulate a signal to a Field Device. 0-10 vdc, 4-20 mA, 0-20 PSI, 0-135 ohms etc...

  13. #13
    Join Date
    Mar 2005
    Location
    Virginia
    Posts
    1,144
    They are all transducers in my mind. A transducer is an electronic device that converts "energy" from one form to another.

    When it comes to pnuematics, I use the term transmitter though, it was just how I learned it back in the day.

    I think a lot of people interchange this word, and most people will probably know what your talking about even if you do not use it so called "properly".

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