Operating instructions

10 METTLER TOLEDO DE40/50/51 Density Meter
Density
The here described period of oscillation T is used to calculate the tube factor and from that
the density of the unknown sample. But this period of oscillation is not displayed on the
instrument. The DE40/DE50/DE51 display only the so-called T-value which is directly
related to the period of oscillation T:
Period of oscillation T = T-value • Z • 0.2 µsec • (1/600)
with: Z = 10 for DE50/DE51
Z = 100 for DE40
T-value shown as T on the display of the instrument
So the T-value is an auxiliary value that makes use of the maximum display possibilities of
the instrument, using only digits and no decimals. This gives the maximum resolution
especially for the determination of the stability.
The stability for accepting the measured T-value can be set at three different levels (see
Section 8.3) to reduce measurement time, according to the need of the customer:
Stability 0: The stability of the measured signal (T-value) is waited for: ∆T
val
≤ 4 within 77 s
for the DE50/DE51, and ∆T
val
≤ 1 within 49 s for the DE40. The density is
measured with an accuracy of ±1
*
10
-5
(DE40: ±1
*
10
-4
).
Stability 1: The final T-value is extrapolated with a patented algorithm from the course of the
slope (∆T
val
/∆temp.), and the density is calculated. This cuts the measurement
time about by half while the result (i.e. density) in most cases is identical to that of
stability 0.
Stability 2: The final T-value is extrapolated at an earlier point with a patented algorithm
from the course of the slope (∆T
val
/∆temp.), allowing a slightly higher
uncertainty, and the density is calculated. Thus the measurement time is cut
about by half again, while the density for most of the samples lies within ± 1 or 2
digits of that of stability 0.
End value
Time
End of measurement
with: stability 2 stability 1 stability 0