E019 - Loadcells For The Vacuum Environment
Novatech manufactures loadcells for force measurement with specifications suitable for vacuum use, whether the application requires strict out-gassing characteristics or simply to operate precisely within a negative (relative to atmosphere) pressure environment.
We have experience within various vacuum classifications as shown below.
|Degree of Vacuum||Absolute Pressure Range(Pascal)|
|Low vacuum||1 x 105 to 3 x 103|
|Medium vacuum||3 x 103 to 1 x 10-1|
|High vacuum||1 x 10-1 to 1 x 10-4|
|Very high vacuum||1 x 10-4 to 1 x 10-7 (currently in progress)|
NB The magnitude of absolute pressures is expressed with respect to a theoretically perfect reference vacuum. Typical normal atmospheric pressure is 1 x 105 Pa.(1Pa = 1N/m2)
Vacuum Process Tooling Applications: Very High Vacuum
These loadcells are built from materials exhibiting low out-gassing properties and to high temperature specifications to enable cleaning prior to use in baking processes with a maximum temperature of 250°C (482°F). The baking process produces out-gassing (a product of time and temperature). The lower the temperature specification the better the performance of the loadcell. See Engineering Application sheet E018.
Materials are carefully selected with low vapour pressures and permeability. We can also offer vacuum chamber feed throughs suitable for our loadcell cables.
In addition to vacuum process compatibility these loadcells also need to mechanically withstand and perform without negative pressure effects (see below) however normally vacuum processes are achieved at constant pressures approaching zero absolute.
We cannot certify loadcells to meet specific degassing requirements, we expect the client to test for this following their own cleaning procedures. Once a sample loadcell is tested positively we do undertake to follow strict repeatable manufacturing handling processes.
Industrial Process or R and D Vacuum Applications: eg Space Applications
In these applications we apply mechanical design principles to ensure the force measurement is not affected by pressure fluctuations. Strict manufacturing process techniques are used that eliminate signal fluctuations created by pressure changes to the strain gauges and micro wiring contained within the loadcell. Normal vacuum loadcells do not require the baking process and do not always need to be built to high temperature specifications. They also do not need to offer a low out gassing coefficient. We may also be able to offer a cable feed through if required.
We are happy to work with our clients following test schedules in order to prove loadcell compatibility with their application requirements.