If you are having difficulty setting the zero, this may have to do with the way the machine is set up. The following checks should be made:
Stability: Ensure the machine is stable. A weight should be placed on the back leg to keep the instrument in a fixed position. Even a slight movement can affect your zero reading
Level: Using the bubble level, ensure the machine is horizontal across the plane. Make any adjustments necessary using the levelling screws.
Assembly: Ensure that you have fitted the pendulum arm to the head unit correctly. When you release the pendulum, the clearance between the foot and the head unit should remain constant throughout the swing.
Arm Alignment: With the pendulum arm locked in the raised position, use a spirit level to check that it is horizontal.
Pointer Stop Bracket: When it is in its starting position, the pointer should be parallel to the pendulum arm. If it is off kilter, this may indicate that the pointer stop bracket has been damaged or bent. The pointer stop bracket is located on the central hub and includes a white nylon screw. This acts as a stopper for the pointer. It is carefully positioned and should not be adjusted.
If the leather handle is in a forward position when the pendulum swings, the pointer stop bracket may get caught underneath it, causing it to bend. This will affect the positioning of the white nylon screw.
Always ensure the leather handle is out of the way so that it does not hinder the swing of the pendulum.
Rubber Slider: Although it does not come into contact with the surface, a rubber slider should be fitted when testing the zero. This is to keep the weight of pendulum constant.
If you continue to experience issues, please contact Munro Instruments. Your instrument may need repair or re-calibration.