The RMC supports a wide range of Magnetostrictive Displacement Transducers. To select the type of the transducer and polarity of the drive output, the following settings can be changed:
Support for Pulse-Width Modulated or Start-Stop MDTs.
Support for between 1 and 15 recirculations on PWM MDTs.
Support for using either edge of a Start-Stop pulse. This is required to support some Balluff transducers.
Support for short and long blanking periods. The correct setting of this parameter depends on the transducer housing type. See the description below.
Support for reversing the drive output in software.
These settings are set from software; no jumpers are required. Except for the blanking period, these settings are all in the Configuration word parameter; refer to that help topic for further details. See the descriptions below for details on the blanking period settings.
Blanking Period
The blanking period determines the amount of time to delay before starting the counter for an MDT. The time delay begins after the rising edge of the Start pulse on a Start/Stop MDT or the return pulse on a PWM MDT. Refer to the following diagram:
The reason for the blanking period is to ignore noise that occurs after edges on the Start or PWM pulse. This was especially a problem with older transducers. As shown in the diagram above, noise during the blanking period is ignored.
However, the longer the blanking period is, the longer the minimum distance measurable by the motion controller becomes. That is, if the Stop pulse comes back during the blanking period, it is not registered, and no position can be read. This becomes a problem only with the newer clevis-mount transducers (for example, the IP-67 housing type from Temposonics).
Therefore, to allow for this trade-off, the blanking period can be set through RMCWin to be either 5ms (recommended for clevis-mount transducers) or 21ms (recommended for all other transducers). This setting cannot be changed from a PLC, but must instead be set through RMCWin and saved in the RMC’s Flash memory.
Therefore, to allow for this trade-off, the blanking period may be configured:
On the Tools menu, click Module Configuration.
In the Slots list, click the MDT module you want to edit.
Click Slot options. The MDT Options dialog box will be displayed with a tab for each axis on that slot.
Click the Axis 0 tab.
Click Standard (21ms), unless the transducer on that axis is a clevis-mounted transducer, in which case you would click Short (5ms).
Click the Axis 1 tab.
Click Standard (21ms), unless the transducer on that axis is a clevis-mounted transducer, in which case you would click Short (5ms).
Click Update RMC.
The Update Module Configuration dialog box will be displayed to indicate the progress. If the module could not be reset automatically, you may be prompted to reset the module yourself.
See also:
Copyright (c) 1997-2015 by Delta Computer Systems, Inc.