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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

  • 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?