Analytical Balance

Overview

The analytical balance is a precision laboratory instrument that determines mass to a readability of 0.1 mg within a draft-shielded weighing chamber. It is the standard tool for preparing standards, weighing reagents for quantitative analysis, and gravimetric calibration. Sub-milligram resolution at 220 g full scale demands isolation from air currents, vibration, thermal gradients, and electrostatic charge, which shapes nearly every element of its construction.

Unlike a spring or strain-gauge scale, the balance never deflects under load. The Weigh Cell holds the pan at a fixed null position and reports the electrical effort required to keep it there, giving high resolution and excellent long-term stability.

How it works

A sample placed on the Pan Assembly couples through the draft-shield floor to a monolithic flexure lever inside the weigh cell. As the load tries to deflect the lever, the Position Sensor detects the displacement and the control loop increases current through the Force Coil, which sits in the field of a permanent magnet. The current needed to restore the lever exactly to its null is proportional to the applied mass.

That current is digitized by the Main Board through a high-resolution converter, temperature-compensated against the on-board sensor, and shown on the Display Module. Because the magnet's strength and the local gravity both affect the result, the balance performs automatic span calibration: the Calibration Mechanism lowers an internal reference weight onto the lever and the system corrects its scale factor.

The Draft Shield encloses the pan with sliding glass doors so that air movement does not register as drifting mass. The Housing anchors the cell on a die-cast base and carries the leveling feet and bubble level; the electronic level sensor warns the operator if the instrument tips out of plane, which would otherwise bias the reading. An optional static ionizer neutralizes charge on plastic vessels and powders, while the Interface Board exports results to a LIMS over RS-232, USB, or Ethernet.