Types of rabbur and information about it.

1) Glass Thermometer

- The glass thermometer is one of the best & most common type of temperature measuring device. 

- The unit consist of a glass enveloped a responsible liquid & indicating scale.

- The envelope compressed a thick wall glass tube which a capillary tube & a cylindrical bulb filled with the liquid.

- The two parts are based & fused in together & top end of the capitllary tube is shilied.

- The size of the capillary depends on the size of the sensing bulb, responsive liquid & the desired temperatylture range of the insturument

- The changes in the temperature will caused the fluid tube expamded & rise up to the capillary.

- Sibce the area of the capillary is much less than the bulb.

- The relatively small changes of fluid volumme, will results in significant fluid rise in the capillary.

- The thermometer bulb usyally filld with mercury

>  Chracteristics

1) Simplicity of used & relatively low cost.

2) easily poutable

3) Easy of Checking for Physical damage.

4) No need of additional indicating insturument

5) Range limited to about 30°C.

6) Time up between change in temp.&  thermometer response is due to relatively high heat capacity of the bulb.

2) Bimetalic Thermometer

- when two metal stricks having different Co-efficient of expansion are based on brazed together change in temperature will cause of free deflection of essemble .

- The alloys are used in special nature & setected for there physical poroperty over a broad range of temperature.

- The bimetalic stricks wound in a helix form as showed in figure, basis of the thermometer

- one end of helix is fixed on a fix Sharp & other end is free & attuch with movable shaft which has a pointeet it's end.

- such a strip is subjected to temperture will toti unwined it self & the rototion of movable Shaft is calibrated in turn of temperature

>  Characteristics

1) in expansive

2) Simple compact & rotobust            
constuluction

3) Practically range & accruacy are large or rare 

4) Speed of response are simillar to glass thermometer.

>  Application

-  inportant application in put the switc hing device use in domestic ovens for electric iron, car winker temp. &  the refrigera tor & air conditionar system.

3) Pressure Spring Thermometer

- The system is define as thermal system filled with a gas and operating on the pressure change with temp.change.

- The expansion on a gas is general by the ideal gas law
                  PV = nRT
             for  a constant volume
                  P~T

- The system consist of a temp. senstive filled with exapannding gas the flexible capillary tube a pressure sensitive devich such as bourdan tube & a device for indicator or recording a signal related to the measure  temp. under the inflence of the increasing temp the filled material under goes an  increase in the volume & Puressure

The effect is trasmitted thruough the  fine capillary tube to the bourdan tube which converts to the signal for a more usefull

- This may either be a mechanical  linkage to drive a pointer or may be a Paenumatic or an electrical device to transmit the signal overa long distamce.

N² (Niturogeg) is the gas most often used for such a system because it is chmically inert & having favourable co-effici of eapansion futher it is readily available both in quantity & quality

- The temp.limits of the thermometer is  -130 to 540°C.