Laser Range Finder PDF

37 CHAPTER 2 MME IN THE IAF: FUNCTION, CARE AND MAINTENANCE LASER RANGE FINDER (LRF) 1. Laser Range Finder is an instrument to find out the range (distance) of the obj...

37 CHAPTER 2 MME IN THE IAF: FUNCTION, CARE AND MAINTENANCE LASER RANGE FINDER (LRF) 1. Laser Range Finder is an instrument to find out the range (distance) of the objects. In meteorology, it is used for measuring the distance (height) of clouds. Laser beam is generated and emitted in the atmosphere by this instrument. This beam is reflected by the cloud (object). This reflected laser beam is received by the LRF instrument. Processing unit installed in the instrument calculates the time taken by the laser to return back and calculates the distance of cloud (object). This distance is displayed on display unit in metres. Accessories 2. Laser Range Finder has the following accessories: - (a) Tripod carrying case, rain proof. (b) Tripod stands with Telescopic legs. (c) Case carrying (d) Case nylon (e) Battery Charger (f) AC Adaptor (g) Lens cleaning kit (h) 2 x 14.4 volt batteries Technical Specification 3. Technical specifications of Laser Range Finder are as follows: - (a) Range. Maximum 20,000 m and minimum range 80 m (with attenuation filter). It is advised that filter should be used for ranges less than or equal to 1 km. (b) Accuracy. 5 m. (c) Duty Cycle. One shot every 6 seconds up to 2 minutes followed by one shot every 2 minute up to 8 min.  38 (d) Power Supply. Nickel Cadmium or Lithium rechargeable (14.4 V). (e) Operating Voltage. 10 V to 30 V DC Function Button 4. The functions buttons of LRF are illustrated in Fig. 2.1. Fig. 2.1 Parts of LRF Battery Charging 5. The battery charger (Fig. 2.2) has an option to charge one or two batteries at a time. Insert the battery to be charged in the battery container. Close the container with the battery charger. Keep the Normal / Off / Fast switch on Normal position. The charging indication LED will be off after completion of charging cycle. The time required for charging the battery in normal mode is 16 hours and in fast mode it is 4 hours. Do not use fast mode till urgent / emergency requirement arises as it reduces the battery life.  39 1. On / Off Switch 2. +12V DC Fig. 2.2 - Battery Charger AC Adaptor Operation 6. AC adaptor is used to supply +12 V DC for charging the batteries. Connect AC adaptor cable to 230 V AC mains supply and output to charger battery input by cable supply. Power "ON" LED should glow. Power status LED of charger will glow. Operating Procedure 7. Check the voltage of Ni-Cad (Nickel Cadmium) battery. If it is 12 volt it is ready for use. Open the cap of battery housing of LRF, and insert the battery with positive (+) terminal facing inside the battery compartment. Press the battery cap inwards and turn the cap clock wise to secure the cap in locking position. 8. LRF can be used by holding with hands or it can be mounted on tripod stand (using mounting bracket). Tripod stand provides stable support at the time of ranging a target. 9. Open the lens cover from the front sight channel and laser transmitter window by rotating upwards. 10. Attenuation filter is used for ranging targets of shorter distance and in dusty environment. Adjust the eyepiece by rotating dioptre setting ring till graticule is in sharp focus. Look through the eyepiece and aim the LRF in the direction of the target. The target must be visible within the small circle in the centre of the cross hair. 11. Press the LRF power ON button. The equipment is ready for ranging if green LED glows after pressing power switch, which must be kept pressed during entire range measuring procedure. Press and release the range switch after lightening of green LED in the eyepiece. The range in metres will be displayed in the eyepiece for three seconds.  40 12. If an error (e.g. shaking of hands) occurred during measurement, the display 13. Illumination of the five decimal points below the digits indicates that no reflection has been received or the target is < 50 m or > 20,000 m or the reflectivity of the target is too low to be detected. Installation of LRF on Tripod (Fig. 2.3) 14. Fix the mounting bracket on the tripod with the mounting stud provided on the stand. Mount the LRF into the mounting bracket. 15. Insert the dovetail (union) of the bracket into the matching groove provided on the back panel of the LRF and tighten the locking nut provided with mounting bracket. The LRF is ready for use. Fig. 2.3 - Tripod End of Operation 16. After the completion of cloud observation follow the following procedure: (a) Take out the attenuation filter (if used). (b) Close the lens cover. (c) Remove the battery from the LRF. (d) Repack the LRF and accessories in the case Nylon and case carrying.  41 Remote Control Unit (RCU) 17. Remote Control Unit can also be used for operating the Laser Range Finder. This unit operates with 4 x 1.5 V AA size batteries and has two switches, for switching the power on/off and finding the range. 18. For operating laser range finder through remote control unit, connect the RCU cable to the LRF. Switch on the RCU On / Off button. It powers RCU from 4 x 1.5 V which indicates the connectivity between RCU and LRF. Power switch should be kept 19. condition. By pressing range switch, fire command is activated in LRF. Following messages can be displayed on the LCD of RCU after activating fire command: - (a) Display. Target range (distance) in alpha numeric display in meters. (b) RM BT LO. This message is displayed when RCU batteries are discharged and need replacement. (c) No Target. This message is displayed as default when RCU and LRF indicates that there is no target within 80 m to 20475 m. (d) NSP. No start pulse message indicates problem in LRF. (e) NO MAXR. No maximum range message indicates problem in LRF. (f) Supply LO. Supply low indicates LRF battery has to be recharge and replaced. (g) Comm ERRS. Communication error is displayed when communication is not established between LRF and RCU. (h) LRF and RCU. When this message is displayed LRF will not be operated with RCU. 20. Use of LRF to Determine Visibility Landmarks. The equipment may be used to determine visibility landmarks in and around the airfield. However, general precautionary measures are to be strictly adhered while operating the equipment in a short range. Attenuation filter must be used while determining the distance of an object within a range of 1 km or less. 21. Laser light generated by this equipment can cause serious damage to human eye. The following precaution must be taken while handling the Laser Range Finder.  42 (a) Proper precaution is to be taken while handling this sophisticated equipment. (b) Check the battery voltage with the help of multimeter before inserting the battery in the battery compartment. (c) Ensure the battery is removed when equipment is not in use. (d) Charge the, batteries regularly once in a month. (e) Close rubber lens cover (provided additionally) or the metallic lens cover when the equipment is not in used. (f) Clean the optical surfaces of the equipment with lens paper sheet and brush which is being provided as cleaning kit. (g) Use tripod stand to avoid error. (h) Use normal mode of charging as far as possible until unless urgent/emergency requirement arises, as fast mode reduces the life of the battery significantly. (j) Use Attenuation filter while ranging targets of shorter distance and in dusty environment. (k) Maintenance carried out by the operator at unit level is restricted to cleaning and inspection of external surfaces, lenses and window only. (a) LRF-LH 30 is a sophisticated electro-optical instrument. Don't drop/hit LRF on the hard surface. (b) Don't look into the laser beam. Do not point towards the human being. (c) Don't operate the LRF in a confined space/closed room. (d) Don't dispose the LRF batteries in fire. It may explode. (e) Don't apply extra pressure on switches. (f) Don't clean the lens with rough cloth. (g) Don't short the battery terminals. It can damage the battery permanently. (h) No unauthorised/unskilled person should open the LRF for repairs.  43 (j) If green LED doesn't glow in eyepiece within 5 seconds after switching on the power switch, release the power switch and check the voltage of the battery. (k) Do not exceed more than prescribed measurement per minute. (l) Do not charge the battery in fast mode except in extreme emergency. References 1. Procedures for IAF Met Service - IAP 3202 2. Reference Manual