The TORBAL model EA-1 balance is a null type single pan balance using taut metal bands as the fulcra in place of knife edges or friction pivots. Placing an object on the pan displaces the beam from its zero position. Through substitution weighing combined with electronic control, the beam is returned to its zero position. The digital indication shows how much weight change was required to accomplish this.
The capacity of the balance is 160 g. with a precision (standard deviation) of ±0.03 mg. The smallest directly readable value is 0.1 mg. and estimation can be made to within 0.05 mg.
The following practices must be adhered to in the use of the balance:
1. Solid chemicals are not to be placed directly on the pan.
2. Spills of solids or liquids must be cleaned up at once.
a. Solids can be brushed from the pan on to the floor of the balance and then swept
out of the balance with the small brush provided for that purpose. The pan and
bow should be held gently, but firmly together as a unit when brushing material
from the pan.
b. Liquid spills on the pan should be cleaned by removal of pan from the balance
and rinsing the pan with deionized water followed by thorough drying of the
pan with tissue (Kimwipes). At no time should the pan be handled with the
bare fingers. Place the “dried” pan on a clean watch glass in an oven at
110°C. for 15 minutes; remove and allow 15 minutes for cooling to room
temperature. Check pan to see that it is lint free. Replace pan in balance.
c. Spills on the floor of the weighing chamber should be taken up with tissue,
and then the area wiped several times with moistened tissue and finally
wiped with dry tissue. (In the case of liquid spills, students should carry
out the clean-up in the presence of their instructor).
3. All objects to be weighed should be at room temperature.
4. Do not bump or lean on the balance tables.