Messtechnik Sachs Irinos IR, User Manual

Page: 148 / 214

148
Irinos IR Users Manual © 2015 - 2016 Messtechnik Sachs GmbH, Germany
Measurement / Control via MscDll
2880 Bytes for the
// measurement values; assign these buffers to the MscDll
for (i = 0; i < 2; i++) {
buffer[i] = malloc(720*4);
result = MSC_AttachSubChannelBuffer(pDevice, opcRDM1, i,
720*4, &buffer[i]);
if (result != MSC_STATUS_SUCCESS) return -5;
}
// Activate trigger
ansiString = “ #1# ”;
WriteCommandStr(opcAT, ansiString);
if (ansiString != “ #0# ”) return -6; // An error occured: cancel
starting measurement
// An error occured: cancel starting measurement
do {
result = MSC_GetPosition(pDevice, opcRDM1, &nSamples);
if (result != MSC_STATUS_SUCCESS) return -7;
Sleep(50); // Take a break for 50ms
} while (nSamples < 720);
// Inactivate trigger
ansiString = “ #1# ”;
WriteCommandStr(opcIT, ansiString);
// The measurement values are available now and can be used for
further processing
Starting the dynamic measurement
A common problem with such measurements is the start of the
dynamic measurement. In the example above, the start position 0 is
expected. This works only, if the rotational disk is turned backwards,
until the incremental encoder T12 has a negative value. This neither
always possible, nor does it make sense.
In order to solve this problem, the position of the incremental
encoder T12 can be set to a negative value by software. The
function
MSC_WriteCommand
together with the opcode
opcSP
(0x35)
must be used for this purpose. If the incremental encoder has an
index signal, the following solution is a good choice:
a) Before starting the measurement, the position of the incremental
encoder is set to a negative value, e.g. -100.000. Simultaneously
the index evaluation is activated.
b) Measurement is started. The drive starts turning.
c) If the incremental encoder crosses the index signal, the position
of the incremental encoder is set to 0. The dynamic
measurement now starts sampling the measurement values.