GB2245973A - Level monitoring using fibre-optic links - Google Patents

Abstract

A level monitoring system employing fibre-optic links 5 for level detection of flammable and non-flammable liquids. The system is built in order to eliminate the use of intrinsic safety apparatus and can be employed in areas of high electromagnetic interference and noise. A rack 3 and pinion mechanism is incorporated translating the rotational motion of the float, resulting from the varying liquid level, into a linear motion. The position of a variable optical attenuator 4 mounted on the rack 3 determines the amount of light, which is sent from a light source via fibre-optic links 5, to a light detector. <IMAGE>

Description

PANEL A Level Monitoring Using Fibre-Optic Links This invention relates to level monitoring using fibre-optic links.

Electrical techniques employed for monitoring the level of liquids are prone to electromagnetic interference and noise. They necessitate the use of intrinsic safety when monitoring the level of hazardous liquids. Non-electrical techniques have a slow response time and are problematical if remote indication is required.

According to the present invention there is a level monitoring system comprising a floater, a rack and pinion mechanism, a variable optical attenuator fixed onto the rack and fibre-optic links for signal transmission and feedback.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Figure 1 shows in perspective, the floater, the rack and pinion mechanism and the variable optical attenuator secured onto the rack.

Figure 2 shows in perspective, the variable optical attenuator and the fibre-optic links employed for the light transmission and feedback.

Figure 3 illustrates a system employed for level monitoring in an open tank containing a flammable liquid.

Referring the drawing the level monitoring system comprises a pinion 2 secured to the floater 1 by, for example a bolt, catch or similar means (not shown). A rack 3 is provided underneath the pinion 2 and the rotational motion of the pinion 2, resulting from the floater 1 motion, is translated into linear motion by means of the rack 3 as shown in figure 1.

The variable optical attenuator 4 secured on the rack 3 by, for example bolts, catches or similar means (not shown), moves linearly thus following the motion of the rack 3. The variable optical attenuator 4 is constructed by mixing gelatine with distilled water and Indian ink. The mixture is then sandwiched between two microscope cover glasses thus forming a wedge.

PANEL B Fibre-optic links 5 are mounted and supported by, for example clamps, or other means (not shown) on either side of the variable optical attenuator 4 as shown in Figure 2. The fibre-optic links 5 are centred and fixed onto a base of a frame (not shown) where the rack 3 slides linearly.

A light source 6 and a light detector 7 are employed on either side of the fibre-optic links 5 as shown in Figure 3. A fixed amount of light is fed from the light source 6 into one of the optical-fibre links 5. The amount of light detected by the light detector 7 depends on the position of the variable optical attenuator 4. The position of the variable optical attenuator 4 depends on the position of the floater 1. The position of the floater 1 depends on the level of the flammable liquid 8 which is held in the open tank 9 as shown in Figure 3.

Claims (4)

1. PANEL C

   Claims 1A level monitoring system comprising fibre-optic links for light transmission and feedback, and a variable optical attenuator which is secured to the rack of a rack and pinion mechanism and its position determines the amount of light to be detected by a light detector.
2. 2 A rack and pinion mechanism as claimed in Claim 1 which is translating the rotational motion of a floater, which depends on the liquid level, into a linear motion.
3. 3 A variable optical attenuator as claimed in Claim 1 which moves linearly following the movement of the rack and determines the amount of light to be transmitted via the fibre-optic link and detected by the light detector.
4. 4 A variable optical attenuator as claimed in Claim 1 or Claim 3 which is constructed by preparing a mixture of gelatine with distilled water and Indian ink, which is sandwiched between two microscope cover glasses forming a wedge.