Operating instructions

METTLER TOLEDO DE40/50/51 Density Meter 11
3.3 Construction of the measuring cell and temperature control
For correct density measurements a very accurate temperature control and measurement
must be guaranteed.
As the temperature in the sample can not be measured directly without disturbing the
measurement of the oscillation, a different approach is used. The temperature is measured
in three different spots:
- temperature 1: sensor placed in the measuring cell, directly over the surface of the
measurement tube. This temperature is shown on the status display (cell
temperature).
- temperature 2: temperature of the thermoblock, not displayed (block temperature).
- temperature 3: reference temperature inside the instrument, not displayed (ambient
temperature).
From these three temperatures the actual temperature in the sample is calculated with a
patented algorithm.
Peltier element
Oscillator /
Vibration meter
Thermal insulation
Sample outlet
Sample inlet
Magnet Temperature sensor 1
(cell temperature)
Measurement tube
Temperature sensor 2
(block temperature)
Temperature sensor 3 (ambient temperature)
Thermoblock
Temperature controller
The cell temperature is compared with the inputted set temperature. The temperature
controller uses this cellblock/set difference to control the thermoelectric module (Peltier
element) which heats or cools the thermostatic block accordingly.
Density