Answer / deepak sharmad

an analog input/output is jsut the variable signal which
come and go to the field instruments linearly in the form
of 4-20 ma.
while the digital input/output is the signal which comes in
the form of 0 or 1 that is for the motor/pumps start stop
and their feedbacks.

Answer / george mathews

Analog signal is the signal that we get in the form 4 - 20
mA. form the instrument on the field. It is categorized as
AI & AO depending upon their movement either from instrument
to DCS or from DCS to Instrument. IT it is from DCS to Field
instrument it is called AO , and if it is from Field
Instrument to DCS it is called AI.

Like wish Digital value are in 1 and 0 form. And we
categorized DI and DO the same way we do in case of AI & AO.
From DCS to Field Instrument it is DO and form Field
instrument to DCS it is called DI.

The main deference between analogue and digital signal is
that in a AI & AO signal the command defince what is the
present status of any instrument ( 4mA = 0%,8ma = 25%, 12ma
= 50% , 16ma = 75% , 20ma = 100% open or close.)

But in DI & DO we have only 1 & 0 , so either with this
command we can either open and close any device 100%. (ie
100% open or 100% close.)

Answer / yousuf

In instrumentation the analog refers to the(4-20ma).

when the analog signal(4-20ma) goes to the input module in
the control system that is called analog input.
eg. the output of pressure transmitter

when the analog signal(4-20ma) comes from the output module
to the final control element in the field ie called analog
output.
eg. control valve

the digital signal in the instrumentation system varies
according to the application for eg we can take two states
on and off for off state the signal is 0v and the on state
the voltage 24v

digital inputs means the signal goes to the digital module
for eg the signal of pressure ,flow ,temperature switch.

digital output means the signal comes from the digital
output module for eg the signal to solenoid valve in the
esd valves

Answer / veera

transmitter output are AI ,
control valve input are AO ,
all process variable switch are DI,
SOV and light on starts condition are DO,

Answer / abdul rehman

Ai means analog input which goes to dcs from control valve or pt or lt and any instrument which opperate to analog signal 4 to 20 ma.
Ao means analog output which goes to valve from dcs madules in 4 to 20 ma.

Answer / mike

Analog input is the signal that a building automated system is telling a device or motor to do. The analog output is what the device or motor is actually doing. So let's say your Building automated system is telling your air handler main fan to run at 20%. That's your analog input. Your analog out put should be the same 20% signal from the controller and you fan should be running at 20%. If your input is 20% but your output is 0% and the fan is not running chances are you have a bad controller or there is a safety device that is preventing the controller to send the 20% output to your fan motor.

Answer / saravanan m

analog input and output signal is nothing but they are
formed as a physical quantity,they should be measured and
indicating using any analog devices. example ac current
represent as sine wave form
analog and digital signals can possible to convert from one
form to another using DAC or ADC
but the digital input and output signals having two level
if they high means 1 or low means 0 example : same sine
wave represent as 0s and is at binary representation

Answer / alex

if the signals (input or output) r in the form of binary
say 0 or 1(only 2 status) is called DI or DO. if the signal
is variable one, then it is called analog signal.

Answer / jaiu

anlog input means anlog indicator pressure
guage and etc.
Digital input -output on-off ya off ex. relay

Answer / rajesh

analog input output is nothing but pressure guages , analog
meters etc

digital output is 4 - 20 mA of signal , digital multimeters
etc

analog input output can be recognized by sensors

while signal cond devices will convert analog and digital is
measured

how the 2.5bar pressure able to control the 40bar steam

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