Recalibration required following Range Change (LRV/URV only) ?

Hi there,

              We have recently purchased two new MicroMotion Coriolis flow meters (ISO17025 calibration included with purchase).

A LRV-URV range of 0-150 Kg/min was specified, and was delivered. However, due to a project miscommunication, it is now necessary to increase the LRV-URV range from 0-150kg/min to 0-200kg/min.

Two questions arise

1. As this would be a LRV-URV range change only (flow calibration coefficients would not be altered), would it have any adverse impact on the accuracy or performance of the meter  ?

2. Would this range change technically invalidate the previous ISO17025 calibration ? And so a recalibration is necessary ?

Thanks

James

  • That is cool and let me know if you need anything from the factory!

    Mark

    On Sep 3, 2020, at 4:48 AM, James Collins <bounce-James_Collins@emersonexchange365.com> wrote:

    
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    James Collins [emersonexchange365.com]

    Hi there,               We have recently purchased two new MicroMotion Coriolis flow meters (ISO17025 calibration included with purchase). A LRV-URV range of 0-150 Kg/min was specified,

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    Mark Bell

    Emerson Process Management, Micro Motion

  • 3ft will work I will need 24 foot or whatever I ordered
     
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  • Hi James - I'm not sure if this forum is working properly (the replies below don't seem to address your original inquiry) so just in case, I will clarify here. In short, the answer to your questions about LRV-URV range is No and No. The range you're referring to is actually the analog output span, not the actual "wetted" calibration range. For meters that have a linear signal response (like Coriolis meters), the range of the outputs does not contribute to the uncertainty of the meter at a given flow rate. For this reason, the analog span does not have to match the wetted flow rates used to calibrate the meter (as reflected on your ISO 17025 accredited calibration certificate). Therefore, changing the analog span on your Coriolis meter does not affect the ISO accreditation of the meter nor its stated accuracy specification, and does not require a new wetted calibration . However - it's worth mentioning there is a very slight "span" effect that applies to all electronics with analog outputs - for Micro Motion transmitters, there is a roughly +/-4 uA (micro-amps) uncertainty that applies linearly per output reading. For example: [if 20 mA =150 kg/min], at the max rate of 150 kg/min the span error is 20mA +/- 4uA (or approx +/-0.02%); [if 20 mA = 200 kg/min] at a flow rate of 150 kg/min the span error is 16mA +/- 4uA (or approx +/-0.025%). Does that make sense?
  • In reply to Jared Drennen:

    Hi Jared, thanks for the clear and detailed reply. It has answered both queries fully.

    Cheers
  • In reply to Jared Drennen:

    I will tentatively concur with Jared. You should be able to reconfigure your output span without a significant impact on accuracy. I suspect that forgetting to calibrate your analog input with your control system input creates a far greater error. If you are using a databus instead of the analog signal, you don't even have to worry about the loss of resolution in the analog output. Given the massive turn-down (dynamic range) of the instrument, it's almost a shame to not use a data bus, unless your process doesn't vary.

    My only caveat is that this won't work if you bought a meter that was sized barely large enough to accommodate the 150 kg/min. You should be able to go back to the data sheet and look up your model number to determine the maximum mass flow for your process fluid (table) or gas (slightly trickier calc) and whether that is above 200 kg/min, but I would be highly surprised if that is an issue.