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on a variety of topics of interest to the environmental measurement community. TNI also hosts two regularly scheduled meetings per year, typically in January and August. Both are a week long and involve open meetings of TNI committees as well as training courses and other special sessions.Standard Interpretation
Standard: 2016
Section: V1M2, Section 5.5.13.1
REQUEST:
The question relates to quarterly calibration verification of manual repeating pipettes where the settings on the mechanical device are (for example) 1-5 step-wise by 0.5, but these settings don't directly correlate to a volume dispensed. It is the choice of tip size used on the device that confers the volume dispensed based on a combination of the tip size and the selected setting on the device. (Here is an example device for reference - https://brandtech.com/product/handystep-repeating-pipettes/).
Is it sufficient to verify the calibration of the device using the range of SETTINGS on the device and one tip size, or does the range of VOLUMES measured with the device and it's multiple tip sizes need to be used instead (which would necessitate using multiple tip sizes and possible difficulty hitting the midpoint range of BOTH settings and volumes)? It is our thought process that using the range of volumes instead of the range of device settings would be verifying both the tips and the device calibration at the same time instead of just the device calibration, while using the device settings would be verifying the calibration of just the mechanical device itself, about which this section is referencing.
TNI FINAL RESPONSE:
The standard requires the range of volumes be verified, including the mid-point of volume of the range of use. An appropriate tip for the volume dispensed must be used to verify the device at the lowest volume, the largest volume, and mid-point volume in the range of use.