New Advanced Technologies forElectronic Precision Balances

A&DCompany,

Limited,aleading

manufacturer of laboratory and industrial
electronic balances, has recently released
the FZ-i Series precision balances (120 ~300g × 1mg, 1200 ~ 3000g × 10mg). Naoto
Izumo, chief engineer in A&D’s research &development

division,

explains

two

principal technologies incorporated in theFZ-i Series.
Background
Social and industrial infrastructures rest upon products supported by technology.
Particularly, weighing products are used in many fields and therefore occupy a role akinto a mother machine for industrials. In this regard, A&D believes that manufacturers ofweighing products assume great responsibility.
For many years, A&D has made an effort to provide high-performance weighing
products at reasonable prices in order to promote technology upgrades in as many fields
as possible. The FZ-i Series is a result of these efforts. Two technological innovations
characterize the FZ-i Series; the Compact Super Hybrid Sensor (C-SHS) and theair-pump controlled, direct-acting internal calibration unit.
C-SHS
Most electronic precision balances adopt an electro-magnetic compensation method fortheir weighing sensors. This method equilibrates the Lorentz (electro-magnetic) force
generated by the electro-magnetic unit at one end of a beam with the weight of theobject placed at the other end. The electro-magnetic unit consists of a force coil and amagnetic circuit, which requires an expensive rare-earth magnet to generate theLorentz force. In order to achieve more competitive pricing for the FZ-i Series, A&D
focused on reducing the size (and consequently the cost) of this magnet for the magneticcircuit.

Of course, reducing the size of the magnet lead to a smaller magnetic force. To
compensate for the diminished magnetic force, A&D invented what we call the “doublelever system.” Using this system, the lever ratio has been dramatically increased (morethan 300 to 1) by means of an integrated second lever (see Figure 1). The double leversystem can only be realized when there is highly precise processing. For example, thesecond lever is made by pressing a material with a thickness of only 1mm, with thethinnest area as thin as 0.3 mm. This kind of highly precise processing is a field inwhich Japan has traditionally excelled. Thanks to the double lever system and otherunique devices enabled by high-precision processing, the production cost of A&D’s
precision weighing sensor has been reduced by as much as three quarters in eight years.

WeightMagnetForce2Force1Force coilab
Fulcrum 1st leverFulcrum

2nd levercd(Figure 1:

Force2 = Force1 × a/b × c/d)

Air-Pump Controlled, Direct-Acting Internal Calibration Unit
Balances with an internal calibration function, while useful, are generally expensive.
By incorporating a mass inside the balance, it becomes possible to easily calibrate abalance and therefore ensure constantly accurate weighing. However, in such balancesa very complex mechanism is also incorporated to move up and down the internal mass,
which results in a substantial cost increase.

Conventionally, the device for moving the mass uses a geared motor. Despite the highcost of the geared motor, it is plagued by a number of inherent problems. For example,
drive failure due to galling of the gear itself, mechanical problems due to increased
complexity of the force transmission mechanism to convert the rotational motion of themotor to the up-and-down motion of the mass, or other problems such as those causedby dust getting inside the high precision driving mechanism.
In order to solve these problems, A&D has changed the rules of the game and adopted a
direct-driving method with a balloon-like actuator, which utilizes air pressure for its
power source. Using this method, the mechanism for generating the driving force has
been significantly simplified to consist of three elements; namely, a low-cost air pump,
an electromagnetic valve and an air container called a “bladder.” When there is an
unexpected interruption to the power supply, the pump will halt and the valve willremain open, naturally releasing the air inside the bladder and automaticallytransferring the mass (load) from the weighing sensor back to the original position. This
provides a fail-safe mechanism for the sensor. With enhanced reliability thanks to thesimplified structure, it has become possible to minimize possible problems that users
might have encountered otherwise.