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D.F. Tester
D.F. Tester S-Type
C.T. Meter
   
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Last Update: 04/04/2014

Product Guide
Circular Texture Meter ASTM :E-2157-01
 

C.T. MeterThe C.T. Meter (Circular Texture Meter) is a road surface macrotexture profiler, in which a CCD (Charged Coupled Device) Laser Displacement Sensor is used. It is designed to measure on the same circular track on which the D.F. Tester measures the dynamic coefficient of friction. There are various methods to characterize road surface macrotexture profiles. The C.T. Meter reports the MPD (Mean Profile Depth) and the RMS (Root Mean Square). The IFI (International Friction Index) can be computed using the C.T. Meter in combination with the D.F. Tester.

This instrument is also contained in the FHWA's (Federal Highway Administration) Measuring
Instrument Guide.

 
  U.S. Patent : US 6,679,106 B1
  European Patents : No.EP1203928
<Designated States>
England , France , German , Italy ,
The Netherlands
  Japanese TradeMark : NIPPOCTRM
Pictures
FRONT VIEW BACK SIDE
FRONT VIEW BACK SIDE
Specifications
 
1. Displacement Sensor : CCD Laser Displacement Sensor
2. Measuring Range of the Laser : 30 mm (65 - 95)
3. Laser Beam Spot Size : ø70 µm
4. Wave Length : 670 mm
5. Vertical Resolution : 3 µm
6. Measuring Radius : 142 mm
7. Number of Samples : 1,024 per revolution
8. Sample Spacing : 0.87 mm (± 0.05 mm)
9. Divides one rotation into 8 segments and computes the MPD and/or RMS of each segment.
10. Number of Samples per segment : 128
11. Tangential velocity : 6 m/min.
Features
 
1. Small (approx. 13 kgs.) and Portable
2. Short time for a measurement (approx. 45 seconds)
3. Reports MPD and RMS with good reproducibility
4. Easy measurement without operator influence
5. An automobile battery (12V DC , 24W) is used for power supply
6. Four directions of data can be obtained in one measurement, i.e., driving direction, perpendicular to the direction of travel, 45° to the direction of the travel, and the whole circumference.

The number of samples per one rotation is 1,024 (892 mm) which is divided into 8 segments
for the computation of each MPD and/or RMS.
Analysis of the individual segments can be performed to examine the profile parallel to the
direction of travel (Segments A and E) and perpendicular to the direction of travel (Segments C and G). The average of B,F and D,H indicates MPD for 45° to the direction of travel.
The overall MPD can also be obtained as an average of the A through H segments.

Measuring Principles
 

The displacement sensor for this instrument is a CCD which is mounted on an arm that rotates at 80 mm above the surface in a circumference of 142 mm radius. The arm is driven by a D.C. Motor at a tangential velocity of 6 m/min. The CCD is sampled 1,024 times per revolution providing a sample spacing of 0.87 mm by an A/D converter. The data are recorded in memory in a notebook computer. The data are segmented into eight 111.5 mm arcs of 128 samples each. The computer software computes the MPD and/or the RMS of each segment. Optionally the MPD and RMS can be computed for the middle 100 mm of each segment.

Schematics of the measuring system
Schematics of the measuring system
Use

 

Sidewalks, pavements, floor surfaces of buildings, sports facility floors, etc.
Size & Weight
 

C. T. Meter :
400mm (W) x 400mm (L) x 270mm (H)
13 kgs.

With Carrying Case :
470mm (W) x 590mm (L) x 330mm (H)
24 kgs.

Working Scene
 

 

 
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