PULSED AND ISOLATED 4-20mA ?

Hello everybody ,
I deal in Instrumentation and here i need a clarification ,I have often seen written on the specifications asked by the client side for the instruments.
Like for an example In a Electromagnetic Flow meter it was written pulse should be = 10 – 18000 pulses per hour

And for an Ultrasonic Level Transmitter It was written ---- Analog i/p 4-20 mA DC (Isolated)

and similarly --- Output is 4-20 mA DC (Pulsed)

The main query is WHAT DOES THIS PULSE REFER TO ?
WHAT IS THE DIFFERENCE B/W PULSED AND ISOLATED (4-20mA DC)
and HOW TO SELECT THIS SPECIFICATION.

Thanks and Regards in advance

The "Output is 4-20 mA DC (Pulsed)" does not make any sense.
The other two should be obvious.

Ask the author of the specification what is meant by "Output is 4-20 mA DC (Pulsed)".

JesperMP said:

The "Output is 4-20 mA DC (Pulsed)" does not make any sense.
The other two should be obvious.

Ask the author of the specification what is meant by "Output is 4-20 mA DC (Pulsed)".

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Thanks for your reply i am here by attaching the specifications as mentioned from the client side

Read it again there is or in it.

TurpoUrpo said:

Read it again there is or in it.

Click to expand...

accepted ,

finally what is the difference ,if u can provide me any link ,or explain

Thanks

Difference of what? It reads:

4-20ma or pulsed

Click to expand...

Sounds like: one is a standard analog output. The other is a PWM output.

Siemens has an ultrasonic level transmitter with a digital output "Sonar Bero PXS300". The level varies with the frequency. If you count the number of pulses over a certain time, you can find out the volume in the tank.

The specification allows for the level measuring device to have either 4-20ma continuous signal 'or' a pulse output.

Pulse output on a magmeter makes sense because it represents a totalizer output, one pulse for every so many volume units; like, 1 pulse per 10L. Pulse output doesn't particularly make sense on a level transmitter, regardless of its technology.

Pulse (frequency) output on continuous level device is not common, in fact, I am unaware of any continuous level device that has a frequency output.

The "Sonar Bero PXS300" mentioned is described on the Siemens site as a sonar proximity switch, and the material I read shows it has a switched output (absence/presence) or an analog output or a BCD digital output. Frequency was not mentioned except for the transducer's ultrasonic frequency itself, not as a field useable output.

The spec for the flow computer allows for whatever signal comes from the level sensor:
input : from level measuring unit.

So you use the 4-20mA from the ultrasonic level transmitter to feed the input of the flow computer. It's done every day that way, unless you combine the flow computer and the ultrasonic unit, which is the way many ultrasonic open channel flow meters are available.

Dont be Confused

I think the person who started this thread is a bit confused about the analog signal and the pulse signal.
Deara friend, There is a big difference. You may appreciate the fact that there are many ways in which a particular data can be sent from point 1 to point 2.

Let us consider your point of transducer having either 4-20mA output or 100-18000 pulse output. Now let this be given to a transmitter which has either 4-20mA input or 100-18000 input signal capability. And the output will be 4-20mA signal.

Now what do u mean by isolation. When u talk about 4-20mA signal the issue is whether the voltage required for this signal is sourced by the transmitter or the final recipient device(plc, controller). Usually when the transducer is a voltage source for the 4-20mA signal and also the PLC or controller is also a Voltage source you require to isolate them. This is done by using a signal isolator. Some transmitters are designed to use loop power on output. these transmitters are said to have isolated 4-20mA output.

I think this would give you an idea about what it is.