Q.When measuring samples on an analytical balance, numerical values deviate gradually a little at a time. What are the probable causes of this? And, are there any means of correcting this?
A : Analytical balances are susceptible to the influence of temperature, and changes in the surrounding temperature sometimes cause numerical values to gradually deviate. Various measures including the following are effective in reducing the influence of temperature: 1) Keep changes in temperature of the installation site to a minimum (preferably to 2 °C or below). 2) Leave the balance powered on at all times (in a warm up running state). 3) As far as possible, limit the opening/closing of doors to reduce the intrusion of wind from the outside. And, 4) prevent the air blast from air conditioning from directly striking the balance. Also, the indication of electronic balances, by nature, changes slowly even if the load does not change. Changes near the zero point can be eliminated by turning the "zero tracking" function for canceling out changes near this point ON.
For examples of how the indication changes when the sample or container is charged with static electricity, click here.