Emerson Exchange 365

Flow rate

Dear Reader ,

I have got a basic question

Which part of flow meter is responsible for flow rate

Your reply appreciated

Thanks

Yunnus

Yunus Misbah

• 16 Mar 2017 4:59 AM
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5 Replies

• leirbag

  

  • 16 Mar 2017 6:36 AM

  Sorry, but is a funny question:
  1. There are many different types of flowmeter.
  2. Which are the parts that you find in a flowmeter ?
  
  Yet I will risk an answer: the sensor.

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• Travis Stone

  

  • 17 Mar 2017 11:35 AM

  In reply to leirbag:

  Hi Yunnus,
  
  Thank you for your question.
  
  I must preface my answer by letting you know that your 'basic' question is quite broad, and therefore we must clarify some things before we can find a satisfactory answer.
  
  First of all, as Leirbag indicated, there exists a large variety of 'flow meters', which operate somewhat differently, with different parts, principles, calculations, etc.
  
  For example, Emerson's Rosemount vortex flow meters have a shedding bar inside the flow line which introduces a specific flow obstruction in the middle of the flow line, which causes predictable vibrations (due to vortices) on part of the meter body that makes contact with a piezoelectric sensor. The piezoelectric sensor sends very low voltage signals into a transmitter, which can be interpreted through the electronics, and "output" on a 4 to 20 mA signal by changing the resistance (ohms) of an internal circuit, which affects the current (milliAmps) on the line that provides power (Volts) to the transmitter. This would be an example of a vortex sensor with a transmitter using analog outputs, or a vortex flowmeter.
  
  Emerson's Rosemount Differential Pressure ("dP") flow meters might use an orifice plate, or annubar, or other manner of causing a pressure differential. Pressure is measured on both sides of the restriction using small devices such as capacitance-based transducers to send small electrical changes to a transmitter, where these pressure inputs are used in calculations performed by the electronics to determine the flow rate. This transmitter might have an analog output, like the vortex meter above, or perhaps a digital output method, such as HART variables... but we should leave digital communications for another time.
  
  Emerson's Micro Motion series of coriolis flow meters have a sensor installed in the flow line, which divides the flow into two parallel tubes that vibrate due to the coriolis effect and a drive coil. Pickoff coils detect the frequency of these vibrations and this is communicated (along with temperature from a Resistance Temperature Detector (RTD)) from the sensor, to a transmitter, which can output the flow rate to a control system or display.
  
  These are just a few of the many different kinds of flow meters available from Emerson, with different measurement principles. You may notice some common themes in the operations of these three examples. The flow through the sensor causes some measurable disturbance, which is checked in the transmitter against known and calibrated constant values. The transmitter then outputs the signal over wires to a control / monitoring system, or to a display to indicate the flow rate.
  
  So, (your question) what part of the flow meter is responsible for flow rate?
  The sensor detects the flow and sends signals to the transmitter. The transmitter interprets the signals, checks them against internal configurations and uses formulas to calculate the flow rate. This flow rate is output by the transmitter according the the configured output range (output range 4-20mA output=0-100 kg/hr flow, for example). This output is often received by customer control systems on an input card, with it's own (matching) configured input range (4-20mA input=0-100 kg/hr flow).
  
  I hope this provides some clarity about your inquiry. Let us know if you have more questions or comments.
  
  
  Kind regards,
  Travis

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• Yunus Misbah

  

  • 18 Mar 2017 6:42 PM

  In reply to Travis Stone:

  Hello Travis ,
  Thanks for your wonderful reply , Just to clarify this
  
  When we say a flow meter having minimum flow rate and a maximum flow rate with different model numbers , it is to say that different sensors are used for different models numbers that determine the flow meter capability , am i right ?
  
  Regards,
  Yunus

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• Travis Stone

  

  • 20 Mar 2017 11:23 AM

  In reply to Yunus Misbah:

  Hi Yunus,
  You are correct. Different sensors have different ranges, and the sensor range is indicated in the model code.
  You can find Product Data Sheets (PDS) on Emerson's website for all of Emerson's flow meters, which detail the sensor capabilities, including pressure min/max, temperature min/max, flow min/max, etc. and lists the model code order information. This can be used to decode a model code on an existing device, or to build the model string for a new flowmeter you desire.

  Emerson Sales can also help with this.

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• Yunus Misbah

  

  • 20 Mar 2017 5:43 PM

  In reply to Travis Stone:

  Travis Hi ,
  I wanted to have a clear understanding & your answer is very clear for me ,thank you

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