Measurement Computing PCI-2513 User Manual page 24

PCI-2513 User's Guide
Maximizing encoder accuracy
If there are 512 pulses on A, the encoder position is accurate to within 360°/512.
For a position accuracy of 360°/1024, count both rising edges on A and falling edges on A.
You get maximum accuracy when counting rising and falling edges on A and on B (since B also has 512
pulses.) This gives a position accuracy of 360°/2048.
These different modes are known as X1, X2, and X4.
Connecting the PCI-2513 to an encoder
You can use up to two encoders with each PCI-2513 in your acquisition system. Each A and B signal can be
made as a single-ended connection with respect to common ground.
Differential applications are not supported.
For single-ended applications:

Connect signals A, B, and Z to the counter inputs on the PCI-2513.

Connect each encoder ground to GND.
You can also connect external pull-up resistors to the PCI-2513 counter input terminal blocks by placing a pull-
up resistor between any input channel and the encoder power supply. Choose a pull-up resistor value based on
the encoder's output drive capability and the input impedance of the PCI-2513. Lower values of pull-up resistors
cause less distortion, but also cause the encoder's output driver to pull down with more current.
Connecting external pull-up resistors to the PCI-2513
For open-collector outputs, you can connect external pull-up resistors to the PCI-2513's counter input terminal
blocks. You can place a pull-up resistor between any input channel and the provided +5 V power supply.
Choose a pull-up resistor value based on the encoder's output drive capability and the input impedance of the
PCI-2513. Lower values of pull-up resistors cause less distortion but also cause the encoder's output driver to
pull down with more current.
Wiring to one encoder
2513. The "A" signal must be connected to an even-numbered channel and the associated "B" signal must be
connected to the next [higher] odd-numbered channel. For example, if "A" were connected to CTR0, "B" would
be connected to CTR1.
* Connections can instead be made to the associated screw-terminals of a connected TB-100 terminal connector
option.
: Figure 13 shows the connections for one encoder to a 68-pin SCSI connector on a PCI-
Figure 13. Encoder connections to pins on the SCSI connector*
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Functional Details