A&D Weighing BM-20 - Manual (Page 13)

BM series 11
3.3.
Cautions During Use
(For Precision Weighing)
Note the following items to get accurate weighing data.
Discharge static electricity from the weighing material. When
weighing sample (plastics, insulator, etc.) could have a static
charge, the weight value is influenced. Ground the balance, and
Eliminate the static electricity using the built-in static eliminator.
Try to keep the ambient humidity at or above 45%RH in the room.
Use a metal shield case.
Wipe a charged material (plastic sample etc.) with a damp cloth.
This balance uses a strong magnet as part of the balance assembly,
so please use caution when weighing magnetic materials. If there is
a problem, use the underhook (on the bottom of the balance) to
suspend the material away from the influence of the magnet.
Eliminate temperature differences between the weighed sample and
the environment. When a sample is warmer (cooler) than the ambient
temperature, the sample will appear lighter (heavier) than the true
mass. This error is due to the rising (falling) draft next the sample. If
you touch the sample, the same type error will occur. Do not touch the
sample directly with your hand. Use tweezers or other tools.
Do not drop things upon the weighing pan, or place a weight
beyond the range of the balance on the weighing pan.
Make each weighing gently and quickly to avoid errors due to
changes in the environmental conditions.
We recommend that the fine range ring and separation plate are
used to avoid weighing error caused by drafts when BM-252 displays
a weighing value in unit of 0.01 mg (minimum display: 0.01 mg).
We recommend that the small fine range ring, fine range ring
and separation plate are used to avoid weighing error caused by
drafts when
BM-22 and BM-20 display a weighing value in unit of
0.01 mg and 0.001 mg (minimum display: 0.01 mg and 0.001 mg).
Take into consideration the affect of air buoyancy on a sample
when more accuracy is required.
Do not use a sharp instrument (such as a pencil or ball point pen) to
press the keys, use your finger only.
Press the RE-ZERO key before each weighing to prevent possible
errors.
Avoid foreign matter (dust, liquid or metal fragments) that could get
inside the balance.
Operate your balance gently. Shorten the operation time as much
as possible (Opening and closing door, putting and removing
sample). Use a pair of tweezers to avoid temperature changes due
to heat from inserting your hand into the weighing chamber.
Grounding
Metal case
Charged material
Magnet material
40°C 20°C
Draft
Weighing pan
Fine range ring
BM-252
Shock
BM-20
BM-22
Fine range ring
Small fine range ring