Proceq Equotip 550 User Manual

© 2016 Proceq SA 33
6.4.2 Methods for Setting Up Custom Conversions
The Equotip 550 provides three techniques to accomplish custom con-
versions, each can be used for all of the three different measuring princi-
ples (example HLD  HRC):
One-point method: The Leeb hardness HLD and the hardness in the
desired scale (i.e. HRC) are determined for a reference work piece. A
standard conversion function HLD-HRC is then adapted through vertical
offset until the measured reference data pair lies on the shifted curve.
Two-point method: Two reference samples are tested, one as soft and
one as hard as possible to find two data pairs (i.e. HLD / HRC). A standard
conversion function HLD-HRC is then adapted through adding a straight
line until both of the measured reference data pairs lie on the tilted curve.
Conversion polynomial: If a custom conversion needs to be applied
throughout a wide hardness range, several reference samples shall be
tested to find a stable basis for interpolation. Up to 5th order polynomials
can be programmed into the Equotip 550 indicating device by defining
the polynomial coefficients A
i
in
HRC(HLD) = A
0
+ A
1
· HLD + A
2
· HLD
2
+ A
3
· HLD
3
+ A
4
· HLD
4
+ A
5
· HLD
5
see Equotip Technical Guide under Information  Documents or in the
download section of the Proceq website.
NOTE! When using a polynomial conversion of a higher or-
der, please make sure to have the coefficients with sufficient
digits to avoid inaccuracies in calculations.
6.4.3 Example of a Custom Conversion (Two-Point Method)
The data pairs (640 HLD / 41.5 HRC) and (770 HLD / 54.5 HRC) were
measured on two reference samples made from “special steel”.
To measure “special steel” in the future using an adapted HLD-HRC con-
version, the original HLD-HRC conversion curve for “1 Steel and cast
steel” is tilted using the two data points. In this example, the special
conversion is defined as valid for the range 41 to 55 HRC.
Once this curve has been created, it can be selected via material group
“Customer defined” – “Special steel”, using the hardness scale “HRC
Rockwell C” also see chapter “3.3.1.8 Testing Thin Samples”.
Figure 23: Two-Point Conversion
Table of Contents
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Proceq Equotip 550 Specifications

General

Brand	Proceq
Model	Equotip 550
Category	Test Equipment
Language	English