Density Meter LB 444 SECTION 6. BASICS OF DENSITY MEASUREMENTS
57
Reference Temperature
a) With linear temperature coefficient:
If you use only TC
1
, enter the
average product temperature
as reference
temperature, rather than the Lab temperature of, say, 20°C.
Add a correction value (ρ
P
- ρ
Ref
) · TC
1
to the measured value.
A slightly incorrect value entered as TC
1
is the more significant, the greater
the difference ρ
P
- ρ
Ref
. If one correlates the countrates entered at operating
temperature with the density values obtained at
constant
lab temperature,
the reading will always be equal to the density value calculated at lab tem-
perature.
b) With linear and square temperature coefficient:
In this case, enter the lowest temperature (10°C in the above example) used
for calculation of the temperature coefficient as reference temperature.
Temperature Coefficient Calculation without Table Values
6.1.1.1 Linear temperature coefficient
If you don’t know the temperature coefficient for the product you want to meas-
ure, you can calculate it using the method described below. This requires that a
calibration with at least two value pairs has already been performed at reference
temperature.
a) Fill the measuring path with the product to be measured. The density should
be about the average value of the requested measuring range.
b) Disable temperature compensation (instrument configuration without TC).
c) Start measurement and wait for a short time until the reading shows the
value of the product in the measuring path.
d) Write down the density or concentration value ρ
1
.
e) Read off product temperature ζ
1
, write it down and enter it in reference tem-
perature.
f) Change the temperature of the product in the measuring path through heat-
ing or cooling by approx. 10 to 15°C.
g) Write down this density or concentration value ρ
2
, and also the associated
temperature ζ
2
.
h) Calculate the temperature coefficient as follows:
TC = -
-
-
1
12
2
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