Delta RMC101 Manual de usuario descargar pdf (Pagina 615)

100

101

SSI 6.6

Transducer Interface Modules 6-71

2. Set all options to your desired settings.

3. Click the Axis 1 tab.

4. Set all options to your desired settings.

5. Click Update RMC.

6. 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.

7. In the RMC Configuration dialog box, click Close.

Data Length

SSI devices may be purchased which provide a specific number of bits of data. Some common

values include 13, 24, and 25 bits of data. Set the data length field to match your device.

Certain SSI devices have a number of bits but pad it with a zero, which means the total Data

Length must be one greater than the manufacturer's stated data length.

If the most significant bit from the SSI feedback is set, the RMC100 will see the value as a

negative number and will report a transducer overflow. The counts will go to zero.

Output Format

SSI devices may be purchased which use either Gray code or binary data output. Although the

RMC supports both, binary is preferred. Gray code is generally used internally by most absolute

rotary encoders, but it offers no advantage when the data is transmitted to the RMC over the SSI

interface. More importantly, there are some cases where using Gray code can interfere with

transducer error detection. Under Output Format, click the appropriate option to match your

device.

Error Method

Choose the method of indicating an overflow error on the transducer.

• Bit 20

If bit 20 in the SSI data turns on, or if the SSI data bits are all zeros, the Overflow bit in the

Status word will turn on. While the SSI standard does not specify the use of an overflow bit,

Balluff does provide an overflow bit (bit 20) on some of its BTL-5 series of transducers. When no

magnet is detected, the Balluff transducer sets this bit to indicate an error.

• All Zeros

If the SSI data bits are all zeros, the Overflow bit in the Status word will turn on. Most linear SSI

transducer manufacturers set the SSI data bits to all zeros if a magnet is not detected.

Count Offset

The RMC imposes a restriction that all positions must be specified as a 16-bit value in position

units. A position unit is a user scaled value and therefore is quite flexible. However, there are

limitations to this situation. Consider the following example:

A user is using a 2m-long, 5µm-resolution transducer, and wishes a position unit to equal 10 µm.

Therefore, the scale is set up so that 1 (one) position unit equals 2 (two) counts.

The user wishes to control the positions beginning at 1500 mm and ending at 2000 mm on the

transducer. This would result in position units of 150,000 and 200,000. Because the maximum value

for a 16-bit number is 65,535, this would not work. This is where the Count Offset is used.

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Delta RMC101 Manual de usuario Pagina 615

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