Tecfluid FLOMID-MX - Manual (Page 18)

18
7 STATUS INDICATION
During the normal working mode, some symbols can be displayed on the screen which indicate
the status of the instrument.
If the flow rate has risen above the maximum fluid speed (11 m/s) an asterisk (*) will appear in
front of the flow rate value.
If the total volume counter has over flown (>9.999.999 or < 0 units) an asterisk (*) will appear in
front total volume value.
8
EXAMPLES OF USEFUL CALCULATIONS
Measurement error corrections
The calibration of flow meters is accomplished using, for the liquid, water at 20 o C thus obtaining
a calibration for a liquid of density 1 kg/l and viscosity of 1 mPas. If the flow meter is used with a liquid of
other characteristics from the above specified o for reasons of turbulences in the flow, measurement
errors can be induced.
To correct these types of errors we can modify the value of the body calibration factor Fc
introduced in the configuration of the instrument.
Example 1 - Shortage of volume
If we have a flow meter body which specifies Fc = 0.985, and when we check the volume of a
batch, we find that instead of having 100 litres as programmed, we only have 95 litres (5% less) and we
must apply the following correction:
Fcn = Calibration Factor (new)
= ? (1.03684)
Fc = Calibration Factor (original) = 0.985
V = Expected Volume = 100
Vr = Real Volume = 95
Example 2 - Excess of volume
If we have a flow meter body which specifies Fc = 0.985, and when we check the volume of a
batch, we find that instead of having 100 litres as programmed, we only have 105 litres (5% more) and
we must apply the following correction:
Fcn = Calibration Factor (new)
= ? (0.89545)
Fc = Calibration Factor (original) = 0.985
V = Expected Volume = 100
Vr = Real Volume = 105
Change of units of measurement
In some cases we need to change the measurement units for batching, for example, instead of
working in litres we need to work in kilograms. In this case we will need to know the density of the liquid
(ρ).
To change from litres to kilos we must divide the body calibration factor Fc by the density of the
liquid to obtain the new factor for programming the instrument. For example, if the liquid has a density of
0.9 and the body calibration factor Fc = 0.985, and we must batch in kilos; we will have to introduce Fc =
1.09444 in the basic configuration to be able to preset directly in kilos.
Fcd
= Calibration Factor (new density)
Fc = Calibration Factor (original)
ρ = Density of the liquid in kg/litre
V
V F
= F
r
c
cn
⋅
V
V F
= F
r
c
cn
⋅
ρ
F
= F
c
cd