Mettler Toledo LJ16 Spécifications télécharger pdf (Page 40)

Chapter 4: Environmental Considerations

Vibration

(12/99) 4-9

• Add mass to the scale platform.

• Use a shock-absorbing material such as (1) Fabreeka



pads, (2) coil springs, (3)

railroad ties, or (4) build a sandbox (foundry).

(Fabreeka is a registered trademark of Fabreeka International, Inc.)

Vibration

If a scale vibrates constantly, it might not come to rest long enough to capture an

accurate weight reading. METTLER TOLEDO indicators have built-in filtering systems that

can eliminate most of the effects of vibration. When installing a weigh module system,

you should take steps to reduce any external or internal vibration that the indicator

cannot eliminate.

External Vibration: A scale can be affected by vibration from its foundation or from the

surrounding environment. We recommend finding the source of the vibration and

correcting it to eliminate its effect on the scale. Cutting the floor slab or separating the

scale support frame from surrounding structures can also prevent external vibration from

affecting a scale’s stability.

Internal Vibration: Vibrations produced inside a tank are normally caused by sloshing

liquid or agitation. In large tanks, sloshing can produce low-frequency vibrations that

are difficult to eliminate at the scale indicator. You can reduce sloshing by installing

baffles in a tank. If an agitator and its drive motor are permanently attached to a scale,

you might need to incorporate isolation pads (such as Fabreeka



, available from

METTLER TOLEDO) in the mounting of the weigh modules to minimize the internal

vibration. To improve weighing accuracy, make sure the agitator is stopped while weight

readings are taken.

It is difficult to analyze the effects of vibration that is caused by wind. If high accuracy is

required, we recommend shielding the scale from wind. Any time a tank is located

outdoors, it should be designed to minimize vertical forces resulting from wind.

Temperature Effects

Temperature can affect a weigh module system by causing structural supports to

expand and contract or by exceeding the operating limits of the strain-gauge load cells.

As a tank expands and contracts, it pushes or pulls on attached piping. If the piping

connections are rigid, this can cause weighing errors. The following equation can be

used to calculate the change in the length of a tank as the temperature changes:

∆L = a × L × ∆T

Where:

∆L

= Change in Length

= Coefficient of Linear Expansion

= Original Length

∆T

= Change in Temperature

Table 4-3 lists temperature specifications for METTLER TOLEDO load cells. The

compensated range is the temperature range in which the load cell will meet or exceed

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