A&D Weighing BM-20 - Manual (Page 81)

BM series 79
16.4. Checking The Balance Performance And Environment
The balance is a precision instrument. When the operating environment or the operating method
is inadequate, correct weighing can not be performed. Place a sample on the pan and remove it,
and repeat this several times. If the balance seems to have a problem with repeatability or to
perform improperly, check as described below. If improper performance persists after checking,
contact the local A&D dealer for repair.
Checking that the operating environment or weighing method is proper
Operating environment
Is the weighing table solid enough?
Is the balance level?
Is the operating environment free from vibration and drafts?
Is there a strong electrical or magnetic noise source such as a motor near the balance?
Weighing method
Does the weighing pan rim touch anything? Is the weighing pan assembly installed correctly?
Is
the RE-ZERO key pressed before placing a sample on the weighing pan?
Is the sample placed in the center of the weighing pan?
Is the fine range ring installed for weighing with a minimum display of 0.01 mg for the
BM-252?
Is the fine range ring and small fine range ring installed for weighing with a minimum display of
0.001 mg for the BM-22 and BM-22?
Has the balance been calibrated using the internal mass (one-touch calibration)?
Has the balance been warmed up for one hour before weighing?
Sample and container
Has the sample absorbed or lost moisture due to the ambient conditions such as temperature and
humidity?
Has the temperature of the container been allowed to equalize to the ambient temperature?
Is the sample charged with static electricity?
Is the sample of magnetic material such as iron? There are cautions about weighing magnetic
materials.
Checking that the balance performs properly
Check the balance performance using an external weight. Be sure to place the weight in the
center of the weighing pan.
Check the balance repeatability, linearity and calibrated value using external weights with a
known value.
16.5.
Asking For Repair
If the balance needs service or repair, contact your local A&D dealer.
The balance is a precision instrument. Use much care when handling the balance and observe
the following when transporting the balance.
Use the original packing material for transportation.
Remove the weighing pan, pan support, rings and dust plate from the main unit.