Long pipette

Performance & sizing

Core numbers for matching this unit to your tank and electrical plan.

Power

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Flow rate

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Noise

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Dimensions

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Price range

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Tank fit (L)

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Consumables & maintenance

Follow the manufacturer schedule for seals, impellers, media, and other consumables.

Description

The interesting part of a dosing pipette is the printed scale, because a scale is a measurement claim and claims come in grades. NIST's guidance for package testing under Handbook 133 says it directly: graduations placed on glassware by the manufacturer differ greatly in the precision they indicate, depending on the class of the glassware. For high precision volumetric work the handbook requires a Class A pipet, either a Mohr graduated type or a transfer type, and Class A means the piece is built to the tolerances in ASTM E969. A moulded plastic tube sold for aquarium dosing carries no class and no certificate. Its markings are an indication, not a calibration. Three of NIST's handling rules survive the move from a laboratory bench to a tank, and the first one is the rule nobody follows. On a graduated pipette the water below the lowest graduation is not part of the measurement and must not be dispensed. Empty it into the receiving vessel and the delivered quantity is excessive, which is the ordinary way an aquarist doses more fertiliser than they intended. The same page puts it a second way for the volumetric type: do not blow the remaining water out of the tip, because pipets are calibrated assuming a small amount stays behind on surface tension. The second rule is the wet down. All pipets are calibrated to deliver their marked capacity after the inside has been wetted, so the first draw of a dry pipette is the least accurate one. The third is temperature. Both types are calibrated to deliver at 20 degrees Celsius. NIST also keeps a separate good measurement practice for reading a meniscus, which is worth knowing exists the moment you find yourself squinting at a line. None of this literature mentions aquariums, plastic pipettes, or the length of the tube that the product name sells. The old description's 30 cm had no source and is gone.

Source

• nist.gov — https://www.nist.gov/document/d201-031714-use-pipets-june2014pdf

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