KROHNE ALTOSONIC V EN - Manual (Page 56)

ALTOSONIC V
Operating Manual rev02 E 7.30850.34.00 Page 56 of 106
5.1.3 Operating with the standard density
Products with a known constant homogeneous standard density do not need to be monitored by a
densitometer.
Input of the standard density can be
•
Manually in the running UFP-Program
• Through Modbus
•
Analog input
It is named standard density and not density 15 because of the possibility to have a standard
temperature different from 15°C.
The density at 15°C is calculated through iteration by the input of the standard density in a maximum
of 40 steps or a remainder REM less then 10 -5 :
Diagram for calculation VCF from standard density input:
Input for calculating density at 15°C:
•
T
standard
:[°C] Temperature standard
• ρ
standard
:[kg/m 3 ] Density standard
•
Product type
•
Start value for density at 15°C is the mean value of the high and low limits of the required product
type.
In a maximum of 40 loops:
- Calculate the thermal expansion coefficient α
T
with the new found density 15
- Calculate the C
tl
factor (C
tl standard -->15)
)
- Calculate the new reference density at 15°C by:
) 15 tan (
tan
15
−
=
dard s tl
dard s
C
ρ
ρ
- Calculate the difference between the new found density15 and the last found density15. If the
difference is smaller then 0.001% then the new found density15 is correct, otherwise use the
new found density15 as new input.
- If the density 15 after 40 loops is not found then an alarm is shown on screen and through
Modbus communication.
So now the density at 15°C is found.
ρ
standard
T
Density
standard
Product type
Calculate iterative:
C
tl(standard – 15)
Density ρ
15
ρ 15
, Product type
T
proces
P
proces
Calculation proces:
ρ proces
C
tl (proces – 15)
C
pl proces
Calculation standard:
C
tl(standard - 15)
VCF
T
standard
C
tl (proces - -15)
C
pl proces
ρ 15
Product type