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ml/min into mm/s

Jan Kreft Kreft at cardiff.ac.uk
Wed Jul 22 03:51:11 EST 1998


you need the cross-sectional area of your flow cell. Suppose your flow
cell is 1 mm high and 2 mm wide, you have an area of 2 mm^2. At a linear
flow rate of 0.2 mm per sec (or 12 mm per min), you have a volume of

2 mm^2 x 12 mm = 24 mm^3 = 0.024 ml

that has passed through the cross-section of your flow cell during this
time (1 min). Imagine a rectangular block of volume 0.024 ml made up of
the window through which the liquid passes and the distance this liquid
has flown during your time period. 

You need to calibrate your pump/tubing combination to convert rpm into ml
per min, by use of a balance to measure the liquid volume pumped per time
unit for example. 

Hope this helps,


Dr. Jan-Ulrich Kreft			Phone +44 1222 874000 ext. 6036
School of Pure and Applied Biology	Fax   +44 1222 874305
Cardiff University			E-mail Kreft at cardiff.ac.uk
PO Box 915, Cardiff CF1 3TL, UK

On 21 Jul 1998, Sarah Boyle wrote:

> Dear biofilmers
> could anyone provide me with an equation for converting ml/min into 
> mm/s; when using a peristalsic pump and a flow cell.
> All literature seems to quote 0.2mm/sec as a usual speed, but I am 
> uncertain as to how they arrive at this figure when pump speeds are in 
> rpm and flow rates are in ml/min.
> Surely 0.2mm/s could be highly variable depending on the tube radius?
> Help
> Sarah Boyle
> Research School of Biosciences
> University of Kent
> CT2 7NJ
> 01227 764000 ext. 3023

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