Here we learn about optical pyrometer, advantages of optical pyrometer, disadvantages of optical pyrometer, also learn about Safety tools with images.
Optical Pyrometer :
~ When radiation from heated body at high temperature falls within the visible region of electromagnetic spectrum.
~ An image of radiating source is produced by lens and made coincide with filament of lamp.
~ In optical pyrometer wavelength of radiation accepted is restricted by colour filter and its brightness is compared with standard lamp.
~ In an alternative approach, current through the lamp filament is maintained constant.
~ An optical wedge of absorbing material is moved up and down and its variable thickness accentuates the incoming energy to match the filament.
~ The wedge position is then calibrated for temperature.
~ The pyrometer is calibrated by sighting it upon a black body at various known temperature.
~ However if the temperature of filament is higher than that required for equal brightness, filament become too bright in Fig. 3.7.2(a) and if the temperature of filament is lower, it becomes too dark as shown in Fig. 3.7.2(c).
~ The intensity of light of any wavelength depends upon the current flow through the lamp; the optical pyrometer can be directly calibrated in terms of filament current. But filament current depends on resistances of the filament, therefore modern type of pyrometer are calibrated in terms of resistance of filament.
Temperature-Colour Relationship.
Advantages of optical pyrometer :
State advantages of optical pyrometer.(1) Optical pyrometer is portable.
(2) It can be used to detect the temperature of moving object.
(3) It measures the high temperature with accuracy.
(4) It is also used to detect the temperature at distant places.
Disadvantages of optical pyrometer:
State disadvantages of optical pyrometer.
(1) Device is very costly.
(2) More chances of human error while adjusting the image.
(3) It measures the temperature of only hot surfaces.
Safety Tools
~ Safety tools are used to protect the persons using the electrical equipment and installations from getting electric shocks and injuries associated with electrical hazards.
~ Safety tools are classified into two categories :
1. Primary safety tools
2. Supplementary (or secondary) safety tools
~ Primary safety tools will allow the operator to touch the conducting parts if necessary.
~ Such tools are designed for operating voltages above and below 1000 V
~ Coupling and measuring hooks, insulating and measuring tongs, fuse pullers, voltage indicators, insulating devices and appliances for repair work are some examples of primary
safety tools.
~ Supplementary safety tools are also used in addition to the primary protection devices.
~ This includes dielectric gloves, shoes, mats and insulating pads.
~ Safety tools are used to protect the persons using the electrical equipment and installations from getting electric shocks and injuries associated with electrical hazards.
~ Safety tools are classified into two categories :
1. Primary safety tools
2. Supplementary (or secondary) safety tools
~ Primary safety tools will allow the operator to touch the conducting parts if necessary.
~ Such tools are designed for operating voltages above and below 1000 V
~ Coupling and measuring hooks, insulating and measuring tongs, fuse pullers, voltage indicators, insulating devices and appliances for repair work are some examples of primary
safety tools.
~ Supplementary safety tools are also used in addition to the primary protection devices.
~ This includes dielectric gloves, shoes, mats and insulating pads.
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