Measurement Range and Choice of Film

There are eight types of films with their specific ranges available to cover the measurement range of 0.006 to 300 MPa. The latest type "Extreme Low" covers the range from 0.06 to 0.5 bars.

All slides are supplied in reels of 27 cm and 31 cm respectively. The length of the role depends on the sensitivity and starts at 2 m for “Ultra Extreme Low” up to 10 m for the less sensitive films.

If the expected pressure distribution cannot be covered by using only one film, more film types can be superimposed in order to expand the range.

A quantification of the pressure from the printed images is possible at different levels of accuracy.

The user manual that accompanies each package of Fuji Prescale Film presents two different calibration curves for different types of load cycles – short load contact and continuous load. One is for a 5 seconds load cycle only, the other for constant pressure for 2 minutes. These are examples of applications for short-term and in long-term applications.

The different colours at continuous load and short-term exposure is due to the continuous rupture and to a small extent when the microcapsules are at constant load, so that the same load at a longer period of action leads to a slightly darker result. Fuji guarantees an accuracy of about 10%.

Calibration

Measurements are more accurate when the films are calibrated initially under actual experimental conditions. This is especially advantageous on structured materials, different humidities, temperatures up to 300 °C and preesing duration.

Tiedemann has developed for this purpose the complete calibration system CALTEST. In this system, the film and the surrounding material are placed between two plane-parallel stamps with a known surface area and loaded coaxially with different forces.