KROHNE CORIMASS G-MFM 4085 EN - Manual (Page 70)

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5.13.1 Referred Density (Option)
Referred density is a factory-installed option which expands the type of density outputs available
to three different variations - ”actual” ( normal density output ), ”fixed”, and ”referred”. Any one
of these three options can be selected in Fct. 1.2.5 or Fct. 3.2.5 - the ”DENSITY” function of the
”DISPLAY” submenu. Program ”actual” if the ”Referred” or ”Fixed” Options are not desired.
Referred density corrects the actual density value to a standardised density value based on a
reference temperature. The reference temperature and the slope are programmable. The sign
of the slope coefficient (
α
) is always positive based on the assumption that increasing
temperature decreases the actual density measured. The referred density equation is as
follows:
ρ
r
=
ρ
a
+ α
( t
a
−
t
r
)
where ”
ρ
” is the density and ”t” the temperature. Subscripts ”r” and ”a” indicate
”referred” or ”reference” and ”actual” respectively.
Note that the above equation is linear. Referred density accuracy is determined by how precise
a fit a linear function is to the actual temperature-density relationship of the process over the
range of operating temperatures. Also note that the coefficient,
α
, depends on the temperature
units selected,
°
F or
°
C, as well as the density units selected. The units of
α
are the change in
density per degree change in temperature.
Key strokes for the ”referred density” option shown below - start from the measuring mode:
Key Display Step #
line 1 line 2
→
Fct.(1).0 OPERATOR 1. enter programming mode
2
×↑
Fct.(3).0 INSTALL
→
Fct.3.(1).0 BASIS.PARAM
↑
Fct.3.(2).0 DISPLAY
→
Fct.3.2.(1) CYCL.DISP.
4
×↑
Fct.3.2.(5) DENSITY
→
ACTUAL
↑
FIXED
↑
REFERRED
↵
0.0000000 (g)/cm
3
2. set mass units in this step (or S.G.)
→
0.0000000 g/(cm
3
) 3. set volume units in this step
→
0(.)0000000 g/cm
3
1. set decimal point location in this
step
↵
+ 20.0 REF.TEMP (
°
C) 2. set ref. temp. -
°
F or
°
C, sign &
value
↵
(0).000000 SLOPE/
°
C 6. set slope (
α
) of temp. coefficient
↵
Fct.3.2.(5) DENSITY 7. enter inputs
4
×↵
8. return to measuring mode
5.13.2 Fixed Density (Option):
The ”Fixed Density” Option permits setting a fixed, specific density value for the purpose of
calculating volumetric flowrate and/or volumetric total from mass flow. This is useful when
dealing with pure liquids or liquids with a known, fixed composition when it is desired to know
the volumetric flow referenced to a specific (fixed) density at a specific temperature.