Page 65
Appendix | Thickness Measurement
capaNCDT 6500
Formula for the thickness measurement:
Data channel = Measuring channel 1 + Measuring channel 2
i
The result of the mathematic function is output via the Ethernet interface. It is not
shown on display of the DD6530. The output as analog signal is possible via the
optional available analog output card DO6510, see Chap.
5.2.3
or EtherCAT and an
appropriate output terminal.
Do not change the measuring range of the output channel subsequently, since the
entered offset of the mathematic function refers to this measuring range and this is not
changed automatically. Otherwise you must enter again the mathematic function.
If you do not use the Web interface, you can work with the Ethernet commands, e.g. set
mathematic function „SMF“, see Chap.
6.4.16
.
Note that the offset based on the measuring range of the output channel must be input
here.
Example: Offset 4,000 µm, measuring range of the output channel 10,000 µm. Thus cor-
respond 10,000 µm = 0x3FFFFF and the offset of 4,000 µm = 0x199999
A 6.5
Interpretation of the Measuring Values
During the Ethernet transmission the data format reduces from 24 bit to 21 bit. Thus
0x3FFFFF corresponds 100 % of the measuring range (of output channel), in the exam-
ple 10,000 µm.
During the EtherCAT transmission the data format does not reduce to 21 bit. Thus
0xFFFFFF corresponds 100 % of the measuring range (of output channel), in the exam-
ple 10,000 µm.
A 6.6
Example
Sensor measuring range to small
Measuring range overlap
MR 1 + MR 2 < Offset
MR 1 + MR 2 > Offset
Sensor 1
Sensor 2
Offset
Input
1
Input
2
MR 1
MR 2
Thickness
Sensor 1
Sensor 2
Input
1
Input
2
MR 1
MR 2
Offset
Thickness
MR 1/2: Measuring range sensor 1/2
Distance of the sensors to each other is
too large or thickness measurement is not
always possible at target vibration.
Thickness measurement even possible
at a low target vibration.
The double-sided thickness measurement gets along without complex target layer. The
main advantage is that vibrations of the target do not lead to a measurement uncertainty
if offset and measuring ranges of sensors are well chosen.
The position tolerance of the target is determined from the offset and measuring range
(MR) of sensors.
Summary of Contents for capaNCDT 6500
Page 67: ......
