The core of the HZMD-2001 is a precision thermostatic bath, which provides a temperature-stable measurement environment for petroleum densitometry. Every aspect of the thermostatic bath, including the selection of bath liquid, liquid level height, and usage method, directly affects the temperature control effect and measurement results.

Selection of bath type

The instructions stipulate: Add purified water or demineralized water to the bathtub, and do not use tap water.

Why can't tap water be used: Tap water contains minerals such as calcium and magnesium ions. Long-term heating will form scale on the heating tube and the inner wall of the bathtub. On the one hand, it reduces heating efficiency (scale has poor thermal conductivity), and on the other hand, it increases cleaning difficulty. The shedding of scale may also block the circulation channel, affecting temperature uniformity. Pure water or demineralized water (with minerals removed) will not form scale, and maintenance costs are low.

Adjustment of stirring speed

The stirring speed of the instrument is adjustable. The instruction manual provides a simple principle: if the medium is water, no adjustment is needed; if the medium is glycerin, adjustment is required.

Water has low viscosity and can circulate fully at the default stirring speed, ensuring uniform temperature distribution. Glycerin, with a viscosity much higher than that of water, circulates insufficiently at the same stirring speed, necessitating an increase in rotational speed to ensure consistent temperature throughout the bath. If the temperature of the bath is uneven, measuring the temperature in graduated cylinders placed at different positions will result in deviations, leading to discrepancies in the results.

Requirements for liquid level height

The instruction manual stipulates: The bath liquid level should be approximately 15cm from the upper cover. The design basis for this height is:

After inserting the graduated cylinder into the bathtub, the liquid level of the sample in the graduated cylinder should be lower than that of the bath liquid - only in this way can the sample be fully surrounded by the bath liquid, ensuring that the temperature of the sample is equal to that of the bath liquid. If the liquid level of the bath liquid is too low and the liquid level of the sample in the graduated cylinder is higher than that of the bath liquid, the part exposed to the air will be affected by room temperature and deviate from the set temperature.

Regularly replenish bath liquid

The bath solution will decrease due to evaporation after long-term use, especially at higher temperatures (such as 70-100°C) where evaporation accelerates. Regularly check the liquid level and replenish with the same type of bath solution (purified water) in a timely manner if the liquid level is found to be below the required level, ensuring that the liquid level remains at the correct height.

Stability of ambient temperature during measurement

Special reminder in the instruction manual: In the area where the density measuring cylinder is placed vertically, the ambient temperature change during the experiment should not exceed 2℃. If the ambient temperature changes too much (such as sudden air conditioning shutdown, frequent personnel entry and exit), heat will be transmitted into the sample through the cylinder wall, causing the sample temperature to deviate from the set value, affecting the measurement results. If the laboratory temperature fluctuates significantly, the measuring cylinder should be immersed in the constant temperature bath of the HZMD-2001 for measurement, rather than being left to stand in the air for measurement.