Berthold LB 444 - Calibration Method Details

Density Meter LB 444 SECTION 6. BASICS OF DENSITY MEASUREMENTS
54
Function of Temperature Compensation
The temperature coefficient of a liquid is not constant over a large temperature
range, but usually it increases with rising temperatures. Temperature compen-
sation is carried out according to the following formula:
ρ
Ref
= ρ
M
+ (ζ
P
- ζ
Ref
) · TC
1
+ (ζ
P
- ζ
Ref
)
2
· TC
2
ρ
Ref
= Density value compensated with relative to the reference tempera-
ture
TC
1
= Linear temperature coefficient TC1
TC
2
= Square temperature coefficient TC2
ρ
M
= Measured density value
ζ
P
= Product temperature
ζ
Ref
= Reference temperature
(The terms in Italics refer to the parameters that have to be entered in the Prod-
uct Data menu).
With minor temperature changes (approx. ± 20°C) it suffices, in most cases, to
enter the linear coefficient.
Calculation of the Temperature Coefficients
Example:
Product: HCl - water mixture
Measuring range: 20 - 40 weight % HCl
Temperature range: 10° - 30° C
Unit of measure: g/cm
3
The temperature coefficient at average concentration (30 %) is calculated as
follows:
TC = -
-
-
= -
1.1551- 1.1433
10 30
= 0.00059
12
12
ρρ
ζζ −
ρ
1
= Density in g/cm
3
at ζ
1
ρ
2
= Density in g/cm
3
at ζ
2
Input value: 0.00059 XXX