Yokogawa DM8C/VD6 Liquid Density Analyzer - Manual (Page 52)

< 4. OPERATION >
4-10
IM 12T03A01-02E
The one-point calibration is equal to that omitting the 2nd calibration two-point calibration, so, the two-
point calibration using standard solution and sample liquid is described as follows. Since the following
is described assuming that the density converter is installed in the vicinity of the density detector,
for the connector installed away from the detector, please edit the manual for it and carry out the
calibration according to the manual.
4.4.1 Calibration with Standard Solution
Provide two kinds of standard solution whose density at reference temperatures is already known (*1).
One density (standard solution 1) should be near to the low limit of the measuring range and the other
to the high limit (standard solution 2). Temperature coeffi cients (g/cm
3 /°C) of these standard solutions
should be obtained beforehand.
(*1) When measuring the density of the standard solution, use a hydrometer whose minimum
scale is 0.0005 kg/cm 3 .
Calibration should be made in the following procedure. During calibration, only the density detector
and the density converter are to be drived and the unit to receive output signals from the converter can
remain stopped.
(1) Set the converter to “CAL” mode and input data corresponding to function No. ‘3’, ‘4’, ‘5’, ‘7’, ‘8’
and ‘9’. For pressure compensation, subtract the compensation value obtained in Section 4.3.6
from density of standard solution, and set them to function No. ‘3’ and ‘7’.
(Note) When the compensation value is a minus number, the set value becomes large than the
standard solution density.
(2) Purge the inside of the vibrator with air as follows. Fully close the ball valve “BV1” and the needle
valve “NV4” in the sampling unit. Fully open the needle valve “NV2” and “NV3”, connect an air
pipe to the outlet port of the needle valve “NV3” and blow air for one or two minutes. Pneumatic
pressure should be 0.2 to 0.3 MPa (*2).
(*2) For sample liquid remains in the vibrator, blow it out by 0.05 MPa G pneumatic pressure, and
increase the pressure up to 0.2 to 0.3 MPa to dry the inside of the vibrator.
(3) Pouring 18 to 20 ml of standard solution 1 into the vibrator, avoiding air bubble entering it is
described here.
Firstly, remove the blind plugs from the pouring ports for the standard solution (two places)
located on the detector base plate. Secondly, pour the standard solution into the pouring ort
using the injector (accessory) so that the solution fl ows along the inner wall of the vibrator tube.
Using the pouring port near to the sample inlet is recommended. If the injector is stained, clean it
with alcohol.
(4) Read the measured density value at the reference temperature. It is displayed with the mode
selector switch 3 set to “DSPL” and function No. not displayed.
(5) Since calibration with standard solution 1 is made two times, blow out the used standard solution
from the vibrator. Before blowing, plug the pouring orts (two places), and blow air according to
(2).
(6) Carry out the operations of (3) and (4) to confi rm that the same results as that of (4) is achieved.
(Note) If the result differs from (4), repeat the operations of (3) and (4).
(7) For the calibration 1 computation, press “SET” key at the function No. ‘6’. ‘CAL-1’ fl ashes during
computation and the density at the reference temperature is displayed after the computation
fi nishes (Note 1). Check that this value is the correct density (Note 2) of the standard solution 1.
(Note 1) Time for calibration computation varies with density value difference between pre-
calibration and after-calibration. The larger the difference is, the longer the time is.