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Associate

Join Date: May 2011
Posts: 38

The Difference Between Span and Range

05/25/2011 5:50 AM

Hi,

What is the difference between the span and the range of an instrument, and for what do we use both of them?

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#1

Re: the span and range

05/25/2011 6:32 AM

The range is that difference in minimum and maximum operating parameters that the instrument will withstand without damage.

The span is that part of the above range over which the instrument has been set up to give a 0% to 100% output signal.

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Associate

Join Date: May 2011
Posts: 38
#2
In reply to #1

Re: the span and range

05/25/2011 7:25 AM

Thanks mate,

so as per your answer, we use the span for calibration, while the range for the process operating parameters which should be within the range.

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Engineering Fields - Instrumentation Engineering - New Member

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#3
In reply to #2

Re: the span and range

05/25/2011 11:58 AM

Yes, but when calibrating an instrument, zero and span are used, and both within range. I hope that makes sense.

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#4
In reply to #1

Re: the span and range

05/25/2011 7:24 PM

I hope that wasn't a test question.

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Associate

Join Date: May 2011
Posts: 38
#5
In reply to #4

Re: the span and range

05/26/2011 12:20 AM

I'm a Trainee in worley parsons lmt, so I'm series about it.

Thank you all

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Commentator
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#7
In reply to #5

Re: the span and range

05/26/2011 1:24 PM

Fardan,

I will be using this examples in order to help a little

Suppose that you have this:

1) 0 to 150 Psig, the range is 0 to 150 Psig, 0 for the 0%(4mA) and 150 for the 100%(20mA), the span is 150Psig

2) 20 to 200 Psig, the range is 20 to 200 Psig, 20 for the 0%(4mA) and 200 for the 100%(20mA), the span is 180Psig

3) 40 to 350 °F, the range is 40 to 350 °F, 40 for the 0%(4mA) and 350 for the 100%(20mA), the span is 310°F

the span is: Span = URV(100%) - LRV(0%), or in others word, the units valor traveled through complete range from 0% to 100% , where 0% can be a value different of zero and 100% can be a value different of one hundred.

In some instruments manufacturer the span is equal to the 100% (20mA) value in the units used by the transmitter. (°F, pressure, flow)

The range is the unit valor within of the which the process variable expect to stay or be measured,or controlled.

I hope this help

Regards
JP

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Power-User

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#6

Re: The Difference Between Span and Range

05/26/2011 9:24 AM

Hi Fardan

Span is the range full range of an Instrument.

i.e

0 LRV

100 URV

100 Span

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Associate

Join Date: Oct 2006
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#8

Re: The Difference Between Span and Range

05/28/2011 5:22 PM

Span of the instrument is current operating range .In these limits(Uper and lower range)instrument will work according to calibartion.

Range of the instrument lowest and highest limit there instrument can measure.

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Associate

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Posts: 38
#9

Re: The Difference Between Span and Range

05/29/2011 12:33 AM

Thanks all,

I have understood the difference.

regards

fardan

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Associate

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Posts: 38
#10

Re: The Difference Between Span and Range

05/29/2011 12:51 AM

Thanks Mr Instrument guy,

But somtimes the range will be from minus to plus like I saw a table in Yokogawa catalogue here

http://www.yokogawa.com/fld/pdf/eja/GS01C21B04-00E.pdf

look at the table of span and range limits in right side of first page,

range is -100 to 100, span is 1 to 100,

can we use the rule of span to fined it and how?

span = 100 - (-100) = 200

sorry if I read it in the wrong manner!

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Venezuela - Member - New Member

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#11
In reply to #10

Re: The Difference Between Span and Range

05/29/2011 8:19 PM

Fardan,

I´m not familiarized with yokogawa instruments, but you are correct with the firts page table.

I´m not sure about the yokogawa span, because maybe 1 to 100, mean that 1 is the minimun span possible and 100 is the maximun span posibble for that instrument model.

And, As you said can be from minus to plus.

If you can see Rosemount is a more specific with its data, I´m not a Rosemount vendor

this formule is good, Span = URV-LRV

Regards
JP

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Commentator
India - Member - ADIL MOULA Engineering Fields - Instrumentation Engineering - Adil Moula

Join Date: Jun 2008
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#12

Re: The Difference Between Span and Range

06/10/2011 2:15 PM

Range of a Instrument is the capacity to measure the value more accurately between calibrated scale of its minimum and maximum value . span is difference of minimum and maximum of the scale for that particular range

For eg, range of a temperature transmitter (A)is -50 to 150 degrees so the span of the transmitter should be 200 degrees , if you have a transmitter (B)of say -100 to 100 degrees here span of transmitter is also 200 degrees but you cannot select this transmitter as it is not meeting the range . and if the range of the transmitter(C) say -100 to 200 degrees here the span is 300 deg, also it is meeting the rangeof transmitter (A) , we can select this transmitter for calibrating the transmitter range of -50 to 150degree with a span of 200 deg.calibrated span of the transmitter is 60 to 600 degree reflects that one can keep a range between 60deg or to any range in between to maximum of 600deg, range and span are vital factors to select the transmitter for the required process .

hope you understand .

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Fardan (4); find2am (1); Instruments-guy-SAV (2); jamsshed (1); lyn (1); PWSlack (1); RDGRNR (1); ronron (1)

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