How to check a Rotating Laser Level for Accuracy.

How to check a Rotating Laser

Rotating Laser Levels are great bits of kit for providing levels over both small and large distances. And the cost of a rotating laser level can be expensive. But a rotating laser level that is not accurate is worthless or could potentially cause costly mistakes. So, it is important to know that the rotating laser level you are using is accurate.

Is checking a Rotating Laser Level difficult?

No, checking a rotating laser level is not difficult at all. It should be done methodically and may take some time to check thoroughly. The checking of a rotating laser level is straightforward and a guide to doing a complete level check on a rotating laser level is described on this page.

Checking any Rotating Laser for level accuracy uses the same principle as checking a dumpy or Automatic Level. We should have the same height difference of two points when measured from different positions and different lengths of sight.  However, we should check all four quadrants from the rotating laser level. This means there are more steps involved for the rotating laser level check than the two peg test for checking an Automatic Level.

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Before checking a Rotating Laser Level.

Before checking a rotating laser level, it is important to check the condition of the tripod being used. If the tripod is in poor condition or has excessive movement the accuracy of the rotating laser level will be affected.  A quick inspection of the tripod should identify if there are any issues. A test for the tripod can be found on the page test your tripod.

Have a look at the video below. This tripod is not suitable for mounting any survey equipment. It has to much play in the tripod head.

Guide to checking a rotating laser level for accuracy.

First, setup your tripod on a firm and sturdy surface, one that will support the weight of the tripod and rotating laser level. The location should be an area not subject to vibrations from plant and machinery.  Ensure the top of the tripod is level, use a spirit level if needed.  You should choose a position for the tripod that is close (1m to 2m from the rotating laser/tripod) to a suitable upright surface that can be marked on and another suitable upright surface ideally over 30m away. 

 

How to check a rotating laser level for accuracy. Stage 1 of a rotating laser check
Step 1 of the Rotating Laser Level Check

Set the rotating laser on the tripod securely, square to the closest surface to be marked, and switch on and allow the laser to self-level and start up.  You will be turning the rotating laser 90degrees three times during the course of the test.  If you have a grade laser then ensure that the grades are set to 0% in all directions before attempting to carry out any checks.

How to check a rotating laser level for accuracy. Stages 2 of a rotating laser check
Step 2 of the Rotating Laser Level Check

With the rotating laser switched on you are ready to take some measurements.  Turn on the receiver unit and select the fine tolerance setting for taking all the readings.  Place the receiver on the upright surface (wall), or using an E-Grad Staff in good condition, and move up and down until the receiver is at the given level.  Mark the wall with a suitable horizontal line or note down the reading take on the E-Grad Staff.  Now move to the other wall that is ideally over 30m away in either the opposite or perpendicular direction and place the receiver on the wall or staff and move up and down until the given level is achieved.  Mark the wall with a suitable horizontal line or take a reading on the staff.

How to check a rotating laser level. Stages 3 of a rotating laser check
Step 3 of the Rotating Laser Level Check

Return to the rotating laser and turn off the laser.  Without moving the tripod, release the fixing screw enough to allow the laser to be rotated through 90 degrees.  Switch the rotating laser back on and let it carry out its self-levelling procedure.  Turn on the receiver unit and select the fine tolerance setting for taking all the readings.  Place the receiver on the upright surface (wall), or using an E-Grad Staff in good condition, and move up and down until the receiver is at the given level.  This should be the same level as before, but if there is a difference note this down.  Mark the wall with a suitable horizontal line or note down the reading take on the E-Grad Staff.  Now move to the other wall and place the receiver on the wall or staff and move up and down until the given level is achieved.  Mark the wall with a suitable horizontal line or take a reading on the staff.  At this point you should have the same level (or difference in level if noted) marked as the previous round.  If there is a substantial difference in level (more than the specified manufacturer’s tolerance) then you should get the rotating laser serviced at your preferred survey equipment specialist.  If the levels taken are the same then you should repeat the above process a further two times to check all planes that the rotating laser works in.  If the rotating laser returns the same level each time then all is good.

How to check a rotating laser level. Stages 4of a rotating laser check
Step 4 of the Rotating Laser Level Check

Remember though to always ensure that you have your rotating laser calibrated at least every year to maintain its accuracy throughout its life.

Top Tip for Getting the Best Results When Checking Levels.

Whenever you are checking a rotating laser level, or an Automatic (Dumpy) Level, or a Total Station, make sure that the tripod head is as close to being level as possible. Whenever I am carrying out these checks I like to use a bullseye spirit level like this one I bought from Amazon. Its 65mm diameter so it spans the tripod access hole and is large enough to be easy to set.

Large Bullseye Spirit Level
65mm Large Bullseye Spirit Level.

Is this checking process the same as a getting the Rotating Laser Level Calibrated?

No. all that you have done is to ensure that the rotating laser level you are using is accurate enough for the task you are doing, This is not the same as having the rotating laser level calibrated. During this checking process you have not altered the angle of the rotating laser beam, so you have not calibrated it.

Do I need to have a Rotating Laser Level Calibrated?

Only if you are going to be using it for commercial work. You need to be able to prove all the equipment you use is accurate. A calibration certificate from an independent source is the best way to prove the measuring instruments you are using are accurate.

If you are using laser levels for personal use, then checking them for accuracy is fine. If the rotating laser level is not giving the desired accuracy, then it needs to be adjusted. You maybe able to do this yourself or it may need to be calibrated at your survey equipment suppliers.

How long does a calibration certificate last?

It is generally accepted that calibration certificates last for one year. Depending on how critical your levelling measurements are you may require having your rotating laser level calibrated more often.

A Calibration Certificate only states that on the day of testing (or calibration) that the rotating laser level was working correctly. Your checks to ensure that the rotating laser level is still giving the desired accuracy are crucial to continued levelling success.

How often should you check a rotating laser level?

Rotating Laser Levels should be checked weekly if they are being used constantly. If they are used once a month then they should be checked every time they are used. Rotating Laser Levels should also be checked after periods of prolonged storage or before any critical levelling exercises.

The checking process should be completed as described above and the results recorded. The accuracy results should include the date and the name of the person carrying out the checking process.

Conclusion.

By checking your rotating laser level often and recording the results will prevent costly levelling errors. These checks should not take long and if you are doing them in the same place then setting a level line will speed up the rotating laser level checking procedure.

Setting up levelling base lines is something I do on bigger construction sites and is how I checked the accuracy of a rotating laser level. This exercise was to prove that rotating laser levels are accurate. Once a level base line is established, checking any rotating laser level is easy.

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