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9.2 Various Kinds of Corrections
9.2.1
Phase angle rotation correction
The phase is available only from 0 degree to 360 degrees. If the phase incrementally reaches 360
degrees, it returns to 0 degree, from which it keeps incrementing again. If the phase decreasingly
reaches 0 degrees, it returns to 360 degrees, from which it keeps decreasing again. Accordingly, the
concept of phase angle rotation is incorporated into this density meter and some corrections have been
made so to allow the phase to change to an unlimited extent. In such a manner, this density meter has
overcome the limit that the phase is available only from 0 to 360 degrees, thus realizing high density
measurement.
Phase angle rotation correction refers to obtaining the real phase angle θ
rotations the dummy angle θ
= θ
' + N x 360 (degrees)
θ
2
2
N: Number of rotations
Set N=0 at the time of zero calibration, making the number of rotations to zero for the phase angle
θ
at zero point.
1
If the θ
' exceeds 360 degrees to enter into the next rotation, set N=1. If it again exceeds 360
2
degrees to enter into the rotation after the next rotation, set N=2.
(N will move up to 2 only if the meter is of large diameter and the density is high.)
On the other hand, if θ
N by one (1). In other words, when it goes into the -1st rotation from the 0th one, set N=−1; and
when into the 0th rotation from the 1st one, set N=0.
Note: The description above is the basics regarding the phase angle rotation correction. Normally, it is
all right to use the density meter without being aware of this correction. However, in the event of
measuring high density, etc., special setups and actions may be needed. For details, refer to
Section 9.3.
9.2.2
Liquid temperature correction
The phase tends to change in a straight line with regard to the liquid temperature. In this connection,
liquid temperature correction is performed on θ
△θ={θ
△θ
θ
2
θ
1
α
T
T
0
' belongs to based on the measured values coming before and after.
2
' goes below zero (0) degree to enter into the previous rotation, decrease
2
−α（Τ−Τ
）}− θ
2
０
: Phase difference [degrees]
: Actual phase angle of measurement object liquid [degrees]
: Phase during zero water measurement (degrees)
(Measured during zero calibration, and set in advance as a constant)
: Liquid temperature correction factor (degrees/°C)
: Temperature of measurement object liquid (°C)
: Liquid temperature during zero calibration (°C)
(Measured during zero calibration, and set in advance as a constant)
as follows to obtain the phase difference △θ
2
1
75
6 F 8 A 0 7 8 7
by judging the number of
2
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