40 



The Dalhjj Profile Recorder 



This plane is called the Plane of 

 REFERENCE. Thc plane of reference in the 

 timber sample corresponding to the lines on 

 the record is defined by any selected point on 

 the timber surface to be explored. Having 

 selected a suitable point the exploring roller 

 of the apparatus is set to the point and then 

 the plane through this point parallel to thc 

 plane defined by the surfaces of three studs 

 to which the sample is clamped is the plane 

 of reference from which ordinates to the 

 surface are to be measured. The roller was 

 set on the sample to the point corresponding 

 to Z in Fig. 1. 



A reference to Fig. 2 will make this clear. 

 A, B, C are three supporting studs in the 

 machine. The upper surfaces of these studs 

 define a plane. Let a piece of timber be laid 

 on these three points. Let Z be the point 

 in the upper surface of this piece of timber 

 to which the exploring roller is set. Then 

 a plane through Z parallel to the plane 

 defined by the points A, B, C is the Plane 

 OF reference from which all ordinates are 

 measured to the undulating surface. In all 

 forms of the machine there will be found 

 three supporting studs corresponding to the 

 points A, B, C. These studs may be regarded 

 as three blunted points, the upper surfaces of 

 which define what may be called the Plane 



OF THE MACHINE. 



The plane of reference is parallel to the 

 plane of the machine at a distance from it 

 determined by the particular point in the 

 surface to which the roller is set at the 

 beginning of the process of taking a record. 



The traces of these planes are shown in 

 the vertical elevation Fig. 3. 



If the point Z is in the same plane as the 

 points A, B, C then the plane of the machine 

 and the plane of reference coincide. This 

 condition is practically fulfilled in some 



Fig. 1. Profile curves from an 

 artificially prepared surface 

 of a piece of pine. 



In the original record the da- 

 tum lines are 1 inch apart. 



