How to Check Myzox CL-28 CL-36 Auto Level with a Two-Peg Test Malaysia
How to Check Myzox CL-28 CL-36 Auto Level with a Two-Peg Test Malaysia
A two-peg test is a common field procedure used to check whether an optical auto level's line of sight is providing consistent leveling results.
For contractors, engineers and surveyors using the Myzox CL-28 or CL-36 Auto Level, performing a field check can be useful when measurement accuracy is in doubt, especially after transportation, impact or intensive construction-site use.
The Myzox CL-28 provides 28X magnification and ±2.0 mm accuracy for 1 km double-run leveling, while the CL-36 provides 36X magnification and ±1.0 mm accuracy.
MTM Precision Sdn. Bhd. is an authorized distributor of Myzox in Malaysia, supplying Myzox surveying instruments and accessories for professional applications.
What Is a Two-Peg Test?
A two-peg test is a field method commonly used to evaluate the line-of-sight condition of an optical level.
The test compares the elevation difference between two fixed points using observations taken from different instrument positions.
The objective is to determine whether the line of sight remains appropriately horizontal when the instrument is properly leveled.
A two-peg test is useful for field verification, but it should not be treated as a substitute for professional calibration when documented accuracy is required.
When Should You Perform a Two-Peg Test?
Consider checking your auto level when:
The instrument has been transported to a new site
It has been dropped or knocked
The tripod has fallen
Repeated readings appear inconsistent
Benchmark transfer does not close as expected
The instrument has been used heavily
You are beginning an important project
You suspect the instrument may be out of adjustment
Regular verification can help identify potential problems before incorrect elevations are transferred into construction work.
What Do You Need?
For a basic field test, you will normally need:
Myzox CL-28 or CL-36 Auto Level
Stable surveying tripod
Leveling staff
Two stable reference points
Field book or recording method
Suitable test area
The exact procedure used by your organization should follow its surveying and quality-control requirements.
Step 1: Establish Two Stable Points
Choose two stable points, commonly referred to as Point A and Point B.
The points should be clearly identifiable and should not move during the test.
Avoid locations where:
Ground is soft
Heavy machinery creates vibration
Staff positions may shift
Traffic interferes with observations
A reasonably open and stable area makes the test easier to perform.
Step 2: Position the Auto Level Between the Two Points
Set up the Myzox Auto Level approximately midway between Point A and Point B.
The exact field arrangement should follow the checking procedure being used.
A central instrument position is useful because the sight distances to both staffs are approximately equal.
When sight lengths are balanced, certain line-of-sight effects largely cancel when calculating the elevation difference.
Step 3: Take Readings at Point A and Point B
Properly level the instrument and focus the telescope.
Take a staff reading at Point A.
Record it carefully.
Then take a staff reading at Point B and record that value.
The difference between these readings establishes the reference elevation difference between the two points for the test.
Step 4: Move the Instrument Closer to One Point
Move the auto level to a position significantly closer to one of the two points.
Set up and level the instrument again.
Take new readings at Point A and Point B.
Because the two sight distances are now unequal, a line-of-sight error—if present—can become more apparent in the comparison.
Step 5: Compare the Results
Calculate the elevation difference obtained from the second instrument position and compare it with the reference difference obtained from the approximately central setup.
If the differences agree within the tolerance appropriate to the instrument, test geometry and required work, the level may be performing acceptably.
If there is a significant discrepancy, further inspection or adjustment may be required.
For critical work, follow the manufacturer's procedure or arrange professional instrument inspection.
Why Does the Two-Peg Test Work?
Suppose an auto level has a small line-of-sight error.
When the instrument is positioned approximately midway between two staff locations, both sight distances are similar.
The effect of the error on each observation is therefore also similar and largely cancels when the elevation difference is calculated.
When the instrument is moved much closer to one staff, the sight distances become unequal.
The same error no longer affects both readings equally.
Comparing the two calculated elevation differences can therefore reveal a possible line-of-sight problem.
Common Two-Peg Test Mistakes
Unstable Staff Positions
If Point A or Point B moves during the test, the comparison becomes unreliable.
Staff Not Vertical
A tilted staff can affect the observed reading.
Poor Focusing
Make sure the reticle and staff graduations are properly focused.
Incorrect Recording
A simple transcription error can make a correctly adjusted instrument appear inaccurate.
Tripod Movement
Make sure the tripod is stable during each set of observations.
Poor Test Geometry
If the instrument positions and sight distances are not suitable for the chosen procedure, the test may not clearly reveal the condition being checked.
What If the Auto Level Fails the Test?
Do not immediately attempt internal adjustment unless you are qualified and following the correct manufacturer's procedure.
If a significant discrepancy is confirmed:
Repeat the test to rule out operator error.
Check the tripod and leveling staff.
Confirm that all readings were recorded correctly.
Inspect the instrument for signs of impact or damage.
Arrange professional inspection if the discrepancy remains.
For important engineering work, avoid relying on an instrument whose accuracy is uncertain.
Two-Peg Test vs Calibration
A two-peg test and calibration are not necessarily the same thing.
Two-Peg Test
Useful for:
Field verification
Detecting possible line-of-sight error
Checking an instrument after transportation
Troubleshooting inconsistent readings
Professional Calibration
May involve:
Controlled inspection procedures
Reference equipment
Instrument adjustment where appropriate
Documented results
Calibration certification where required
Project specifications may determine which type of verification is required.
Myzox CL-28 Accuracy
The CL-28 has a specified accuracy of:
±2.0 mm for 1 km double-run leveling
It also provides:
28X magnification
36 mm objective aperture
0.4 m minimum focusing distance
±15′ self-leveling range
Myzox CL-36 Accuracy
The CL-36 has a specified accuracy of:
±1.0 mm for 1 km double-run leveling
It also provides:
36X magnification
36 mm objective aperture
0.4 m minimum focusing distance
±15′ self-leveling range
Because the CL-36 has the higher specified accuracy, maintaining proper instrument condition and good field practice remains particularly important when it is selected for more demanding leveling work.
Frequently Asked Questions
What is a two-peg test for an auto level?
It is a field procedure used to check the line-of-sight performance of an optical leveling instrument.
Should I perform a two-peg test after dropping an auto level?
A field check is advisable after a significant impact. If accuracy remains uncertain, arrange professional inspection.
Can a two-peg test calibrate the instrument?
The test primarily checks performance. Any adjustment should follow the correct manufacturer's procedure and be performed by appropriately qualified personnel.
How often should I check my auto level?
The frequency depends on usage, transportation, project requirements and the consequences of measurement error.
Can I perform the test on a Myzox CL-28?
Yes. The two-peg method is applicable as a field check for optical auto levels such as the CL-28.
Can I perform the test on a Myzox CL-36?
Yes. The same general principle can be used to check the CL-36, subject to the correct procedure and required tolerance.
Myzox CL-28 & CL-36 Auto Level Malaysia
MTM Precision supplies Myzox CL-28, CL-36 and professional surveying equipment in Malaysia.
As an authorized distributor of Myzox in Malaysia, we support contractors, engineers and survey professionals requiring reliable equipment for construction leveling, benchmark transfer and civil engineering work.
Contact MTM Precision
MTM Precision Sdn. Bhd.
Showroom & Service Centre
No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia.
Website: www.mtmpre.com.my
Email: mtmpre@yahoo.com
WhatsApp: +6016-6607346
Contact MTM Precision for enquiries about the Myzox CL-28, CL-36 Auto Level and professional surveying equipment in Malaysia.
16 Aug 2026
