1. Temperature problem: display value drifts in one direction

Possible cause: The balance is not warm enough for preheating; there is a temperature difference between the sample and the surrounding environment, resulting in airflow in the weighing container. The air flowing along the sides of the container produces an upward or downward force, resulting in an incorrect weighing result. This effect is called dynamic buoyancy. This effect does not disappear until the temperature balance is reached. The principle is as follows: cold objects display heavier, warm objects show lighter. This effect can lead to a variety of problems, especially leading to differences in the weighing results of microbalances, semi-microbalances and ultra-microbalances.

Corrective Action: Do not directly weigh the sample taken from the drying oven or refrigerator; the temperature of the sample is the same as the temperature in the laboratory or weighing chamber; use a tweezers to remove the peeled container; do not put your hand in the weighing room; Peeling container with small surface area

2. Moisture/volatilization problem: The display value continues to drift in one direction.

Possible cause: You are measuring the loss quality of the volatile material (eg evaporation of water) or the increased mass of the hygroscopic sample (atmospheric humidification).

Corrective Action: Use a clean and dry peeled container and avoid dust or water droplets on the weighing pan. Use a container with a narrow neck and install a lid or stopper. Do not use cork or cardboard for flasks with a round base. This will increase or deplete a lot of water. It is recommended to use a round bottom flask that is superior to the XP/XS balance.

3. Static problem: Each weighing shows different weighing results. The display value is unstable. The repeatability of the weighing result is poor.

Possible cause: The peeled container or the sample has been charged with static electricity. Low conductivity materials such as glass, plastic, powder or particulate matter cannot or can only remove electrostatic charges very slowly (several hours). This discharge phenomenon is mainly caused by agitation or friction during handling or transport of containers or materials. Dry air below 40% relative humidity increases the risk of this problem. The weighing error is generated by an electrostatic force acting between the sample and the environment. Microbalances, semi-microbalances and analytical balances are affected by electrostatic charges during operation, causing the above errors.

Corrective measures: increase atmospheric humidity; electrostatic discharge is a particularly obvious problem in winter heating rooms. In an air-conditioned room, it is helpful to increase the humidity (relative humidity 45% to 60%) by setting the air conditioner; to shield the electrostatic force; to place the peeled container in a metal container; to use other peeled containers; plastic It is preferable to generate static electricity with glass. Metal is a good material; an antistatic gun is used; however, commercially available products are not effective in all cases; use the destaticizing device provided by METTLER TOLEDO.

4. Magnetic problem: The weighing result of the sample depends on its position on the weighing pan. The repeatability of the weighing result is poor. However, the displayed value has remained stable.

Possible cause: You are weighing a magnetic material. Magnetic and magnetically conductive objects exert mutual attraction. The other forces generated are misinterpreted as loads. Almost all objects made of iron (steel) are highly magnetically (ferromagnetic) to the magnetic force.

Corrective Action: If possible, place the sample in a container made of a material such as a Mu magnetic alloy film to remove the magnetic force. Since the magnetic force decreases with increasing distance, the sample can be moved further away from the weighing pan by using a non-magnetic bracket (eg, beaker, aluminum bracket). In addition, the same effect can be achieved by weighing the lower hook. Most METTLER TOLEDO microbalances, semi-microbalances, analytical balances and precision balances have a lower weighing function.

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