1 Introducon
3
The position of the shadow edge is measured digitally using a CCD element (Fig-
ure 1.4) and is converted to a refractive index value n
D
by a processor inside the
sensor. This value is then transmitted together with the process temperature via an
interconnecting cable to the Indicating transmitter for further processing, display and
transmission.
Figure 1.4 Opcal image detecon
1.3 General safety consideraons
The process medium may be hot or otherwise hazardous. Use shields and protective
clothing adequate for the process medium - do not rely on avoiding contact with the
process medium.
Precautions when removing a standard sensor from the process line :
• Check irst that the process line is depressurized. Open a vent valve to the atmos-
phere.
• For a prism wash system, close a hand valve for the wash medium and disable the
wash valve.
• Loosen the lange or the clamp cautiously, be prepared to tighten again.
• Ensure you are clear of any possible spillage and you have a clear emergency es-
cape path.
• After removal of the sensor, it may be necessary to mount a blind cover for security
reasons.
Note: For the Safe-Drive™ system safety rules, see Section 11.5 and for additional
precautions required by explosive atmosphere, see Section 9.10.2.
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