Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations cowski on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
Analog signal...mA vs. DC?
- Thread starter GTodd
- Start date
4-20mA is a common industrial standard. It provides positive identification of a broken wire (current drops to zero) and has better noise immunity than a voltage-sourcing transducer, especially over long distances. If this is copntroller which will be used in an industrial environment I would definitely go with a mA output.
----------------------------------
Sometimes I only open my mouth to swap feet...
----------------------------------
If all the inputs are coming from within the same machine chassis then stick with 0-5V.
0-5V:
Less hassles providing the excitation.
No offset hassles.
More available sensors.
Sensors often less expensive.
4-20mA:
Only two wires (usually)
Less noise sensitive. (As Scotty sez)
Input scaling easier.
Keith Cress
Flamin Systems, Inc.-
0-5V:
Less hassles providing the excitation.
No offset hassles.
More available sensors.
Sensors often less expensive.
4-20mA:
Only two wires (usually)
Less noise sensitive. (As Scotty sez)
Input scaling easier.
Keith Cress
Flamin Systems, Inc.-
well it is time to vote: 4 to 20 mA !!!
Plesae read FAQ240-1032
My WEB: <
Plesae read FAQ240-1032
My WEB: <
Skogsgurra
Electrical
I wouldn't be so sure. The good old +/-10 V signal has been serving us well in the drive systems field and we seldom see any 4-20 mA. That is process control territory. I think that you should make sure for yourself what you need. A "beauty contest" or popularity vote will not give you the best answer.
What does your controller do? What is it supposed to communicate with? Motor current very often is a V signal. Pressure very often is mA signal. Find out what you are supposed to communicate with and select your inputs accordingly. Many systems have a basic 0-5 V input and a switchable resistor to accept mA signals. Software is then used to change the 0-20 mA into a 4-20 mA signal.
Outputs need a little more design work if you want to have both signal types. There you should find out what the partners are and how they communicate.
Either you know what the signals are and design for that - or you do not know and design to be flexible. It is your choice. Not ours.
Gunnar Englund
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
What does your controller do? What is it supposed to communicate with? Motor current very often is a V signal. Pressure very often is mA signal. Find out what you are supposed to communicate with and select your inputs accordingly. Many systems have a basic 0-5 V input and a switchable resistor to accept mA signals. Software is then used to change the 0-20 mA into a 4-20 mA signal.
Outputs need a little more design work if you want to have both signal types. There you should find out what the partners are and how they communicate.
Either you know what the signals are and design for that - or you do not know and design to be flexible. It is your choice. Not ours.
Gunnar Englund
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
jsummerfield
Electrical
Distance is a factor with 0-5 VDC. Unless the distance is greater than a mile it is not a significant factor for 4-20 mA.
John
John
An important factor is frequency range. A slower signal
can take more filtering or even highfrequency pre-
emphasys.
If there is question about the noise, it would be simpler
to use digital interface.
Plesae read FAQ240-1032
My WEB: <
can take more filtering or even highfrequency pre-
emphasys.
If there is question about the noise, it would be simpler
to use digital interface.
Plesae read FAQ240-1032
My WEB: <
- Status
Similar threads
- Locked
- Question