H&D Fitzgerald

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Frequently Asked questions about Density Meter Calibration

What is the recommended frequency of recalibration/ re-certification of Density Meters?

We recommend that density meters are calibrated when new, and then receive an initial recalibration after 1 year. Thereafter the recalibration interval really depends upon how important the measured densities are to you. Only you will know how important accurate and traceable results are to your organisation.

Our paper ‘How often should I calibrate‘ also offers some general advice.

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How do you calibrate?

Meters can be divided into two groups: those that have their own thermostat – almost all laboratory bench-top meters, and those which cannot control sample temperature – such as hand-held and on-line meters. If a meter can control its own temperature, we set it to stabilise at calibration temperature overnight before starting the calibration. If it cannot control its own temperature, we install it in a temperature controlled chamber.

Once we are confident that the meter is at a constant temperature, we check the displayed temperature reading using a platinum resistance thermometer.

Having determined the error, if any, on the displayed temperature we then calibrate the density measurement by filling the cell with liquid density standards which have been calibrated using our hydrostatic weighing system.

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Can you supply Density Meters?

Yes, providing you also require them to be calibrated by us.

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Can you visit my premises and calibrate my density meters?

Our ISO 17025 accreditation allows us to calibrate bench-top density meters on your site. Hand-held meters and online meters which cannot control sample temperature have to be sent to our laboratory to be calibrated in our temperature controlled chamber.

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What is the target turnaround time?

We aim to return laboratory density meters within 5 working days of receipt. (UK mainland only). On-line meters normally take a few days longer.

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What types of density meter are you able to calibrate?

We can calibrate a wide range of density meters, both in our lab and on site. Please contact us for more information.

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Do you calibrate the temperature indication in my density meter?

If a density meter can measure sample temperature, and almost all models can, then calibration of the temperature sensor is normally the first step before calibrating the density measurement. We would normally calibrate the sensor at the same temperature as we calibrate the density measurement, but can calibrate it at different temperatures if necessary. For meters which do not contain their own temperature controller, we do this by either placing the meter in an environmental chamber or passing thermostated water through the meter.

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At what temperature should I have my density meter calibrated?

You should ask to have your density meter calibrated at the temperature at which you usually use it. Our accreditation permits us to calibrate density meters between 0 and 156°C.

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Over what density range should I have my meter calibrated?

The linearity of density meters differs radically for model to model (and sometimes even between instruments of the same model). We therefore recommend that the calibration range should be restricted to the density range over which the meter is used.

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Can you adjust my density meter?

Depends on the model. Please contact us for more information.

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Can you calibrate optical density meters?

No, sorry. These meters measure optical properties, not liquid density. Search for an accredited lab at UKAS.org.

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Do you service density meters?

We prefer not to, but can normally clean a meter if it arrives too dirty to calibrate. There may be an additional charge for this. If necesary we can arrange to send it to the manufacturer for repairs.

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