Why is it an important consideration when selecting a flow meter?

1. Turndown Ratio of aTurndown Ratio of a
Flow meterFlow meter
Why is it an important consideration when
selecting a flow meter?

2. Turndown ratio – Flow meters
• Turndown ratio is a flow measurement term that
indicates the range of specific flow meter is able to
measure with acceptable accuracy.
• Turndown ratio can be expressed as;
• TR = Q (max) / Q (min)
• Where TR = Turndown Ratio
• Q (max) = Maximum Flow
• Q (min) = Minimum Flow

3. Turndown ratio – Flow meters
• Example #1;
• If a gas to be measured varies between
100000m3/day and 1000000m3/day
• This specific application has a TR = 10:1
• The flow meter required should have a TR
of at least 10:1

4. Turndown ratio – Flow meters
• If the flow meter had a maximum flow of
2000000m3/day then the required
turndown ratio (TR) would be 20:1
• Example #2;
• Consider a 12’’ ruler graduated to a
quarter of an inch.Since the smallest
distance that could be measured is ¼’’

5. Turndown ratio – Flow meters
• The turndown ratio is
• 12’’/ 0.25’’ = 48 i.e, (48:1)
• If the same ruler all the graduated lines
below 2’’ are smudged, then in this case
the turndown ratio would now be
• 12’’ / 2’’ = 6 (6:1)

6. Turndown ratio – Flow meters
• Note;
• Turndown Ratio is one of a number of
considerations when choosing or sourcing
for a flow meter for your application
• TR of a flow meter is mostly affected by
the devices signal-to-noise ratio (S/N
Ratio) which results from the fluid
dynamics of the technology and the type
of sensor employed.

7. THANK YOU !!!
Presentation prepared by ;
Benjamin Kyalo
Technical Sales Engineer
+254735211022
bwkkyalo06@gmail.com
www.google.com/+BenjaminKyalo
Nairobi, Kenya