Choosing a Laser Level

Choosing a LaserThe purpose of this document is to set out some considerations, which hopefully may help when selecting a laser for your requirements. There are hundreds of lasers on the market and some are very much alike and different. There are many things to consider. Some not to important and some very important. So lets look at the most obvious first. Rotating and non-rotating lasers. Rotating lasers emit a collimated beam of laser light as a spot varying in dia from around 3 mm to 15 mm. 360 degree reception of the rotating beam is achieved by a rotating penta prism similar to a lighthouse in operation. This feature allows the laser beam power to be concentrated in a very small area and enables greater range than a 360 degree fixed beam laser which utilizes a conical prism to split the beam into a 360 degree plane of laser light. For this reason the laser beam power is greatly reduced as it spread out over the job sight and much lower operating ranges are achieved. If you are considering operations of more than 100 mts, your selection should be rotating. 360 degree fixed beam lasers work well under these distances and have the advantage of fewer moving parts. Laser construction has progressed enormously recently and rotating laser now have less and less moving parts therefore this is less and less a consideration, although some manufactures persist in producing complicated instruments. Machine compatible. You should consider whether you may now or sometime later require controlling a machine laser system for example a dozer or excavator with your laser. If this may be the case then your selection should be a rotating laser. 99% percent of machine laser receivers are designed to operate with a rotating laser as the internal circuitry is designed to detect a pulsating laser source. If you choose rotating you also have the advantage of operating your laser with machine systems from other manufacturers (e.g. A contractor). Rotating lasers also vary in the rotation speed anywhere from 100 to 1400 rpm the most common being 600 rpm. Although it is sometimes possible to operate a machine system from a laser with 150-rpm rotation speed, some lag will be experienced so stick with 600 or more. Visible beam or infrared (non visible) do you need to see the beam? There are many situations were the ability to see the laser beam is an advantage if not a necessity. For example, a pipe laser were the beam is focus on a target and visualized. Pipe lasers are generally very powerful and easily visualized outdoors. Another example is the interior laser. Although not essential it is very convenient if you can see the laser beam. But some visible beam lasers have very poor beams to visualize outdoors and therefore unless specifically required for interior it doesn't matter.Visible beam diodes have now become popular with manufacturers so expect to see less and less infrared lasers. Some interior lasers are sold without a hand held receiver so given there poor operation in bright light you may require to purchase a hand held receiver for outside operation and this can be a significant expense when purchased separately, so check what you are getting. Remote controlled. Generally remote control features come with interior lasers and make the job much easier. For example when doing ceiling work you dont need to climb up to the laser to make adjustments to grade, scan or other features. In general construction this is less important but does have advantages. You should check to see what functions are available with the remote feature for that laser as the features offered vary between manufacturers. For example some offer grade adjustment and some dont. You should look at the work you intend to do and see if the remote control has features you would use. Lets say you are setting up a line of posts. You have set up the laser in the vertical mode over your first reference point where the first post will be and you now walk to the reference point where the last post will be. You detect the laser beam and find some adjustment to the alignment is required if you have a remote with that feature you can simply make the required adjustments. If not you may require a second person or you may have to walk back and forth making adjustments by trial and error. Fully automatic - compensated - manual. All these term refer to how the laser operates and what you need to do to set it up and start working. The most basic manual lasers have a diode that is basically rigidly mounted to the frame of the laser and have level vials that you adjust to create a level beam. This type of operation is dependent on two things. The calibration of the beam to the level vials, your ability to determine the bubble in the centre of the vial. They can be very inaccurate and do not compensate for any movement of the instrument if knocked or movement created by temperature changes. They are generally manufactured by want to be laser companies so forget these pieces of junk. Compensated lasers have an internal compensator that overcomes the problems associated with the manual versions but also have level vials that the operator has to adjust to bring the level of the laser into the range that can be compensated. The operator sets the unit onto the tripod and adjusts the foot screws to roughly level the instrument. The compensator, then takes care of any small errors in the level of the instrument. If the unit is knocked or moves the laser will stop operation until the set up is checked alerting the operator. Fully automatic lasers are just that fully automatic you put the laser on the tripod providing the tripod is roughly level push the button and the unit self levels and operation begins. Usually these lasers will simply re-level if moved or knocked but some have an elevation alert that alerts the operator if there as been any movement in his set up. There are some that offer automatic in the horizontal plane but only manual in the vertical plane. Accuracy.Dont get to hung up over this specification it really is only significant over large distances as seen in agricultural operation or large construction jobs. For the average builder or concreter 10, 15 even 20 arc seconds is fine and refers to a worst case scenario. Have a look for sure but dont make your decision on just a couple of arc seconds. But if you are hung up, lets have a quick look at the difference between 10 and 15 arc seconds over 30 mts. Here is the formula to convert arc second into millimeters for. 10 arc sec over 30 Mts. 10 arc sec divided by 207.47 multiplied by 30 Mts. = 1.44mm15 arc sec over 30 Mts. 15 arc sec divided by 207.47 multiplied by 30 Mts. = 2.16mmSo as you can see we have a difference of .72 mmSome times spec sheets give these specs in elevation error over a distance and dont list the arc second values at all so here is the formula basically the reverse of the above.Error divided by the distance and multiplied by 207.47. Lets do the above examples backwards.1.44mm error over 30mts1.44mm divided by 30mts and multiplied by 207.47 = 9.958 arc seconds2.16mm error over 30 Mts.2.16mm divided by 30 Mts. and multiplied by 207.47 = 14.93 arc secondsSometimes you will see instruments with specs like 6 mm in 30 Mts. (Or inch in 100 feet) thats about the worst I have seen and that was plus or minus. When you convert this out it is a possible total error of 83 arc seconds. So dont be fooled. Need more info e-mail kent@swiftdsl.com.auKENT FULLERLASER AND MACHINE CONTROL AUST37 KIMBARRA CL KOTARA NSW. 2289 Phone 0419551173