Encoder type for PCI - 6220

[JTMX39]

I am trying to select the correct Rotary Encoder to use on my PCI-6220 card (and PCI-SCB68) and I am getting confused on what style I need. I read on here that a "Push/Pull" is recommended but I'm not sure what type that is. Will the 6220 accept the NPN 5V type? I am just doing angular mesaurements in LabView. Thank you! I am looking at an Omron Encoder and they offer 3 types:

1)Complementary output with this specs:

A, B, and Z

12 VDC −10% to 24 VDC +15%

Output voltage:

VH: Vcc − 3 V min. (Io: 30 mA)

VL: 2 V max. (Io: −30 mA)

Output current: ±30 mA

2)Voltage output (NPN output)

A, B, and Z

5 VDC −5% to 12 VDC +10%

Output resistance: 2 kΩ

Output current: 35 mA max.

Residual voltage: 0.7 V max.

3) Line driver output

A, A-, B, B-, Z, Z-

AM26LS31 equivalent

Output current:

High level (Io): −10 mA

Low level (Is): 10 mA

Output voltage:

Vo: 2.5 V min.

Vs: 0.5 V max.

 

[JTMX39]

Also found this on the Complementary Output:

Complementary Output:

The complementary output has two output transistors (NPN and PNP) as shown below. These two output transistors alternately turn ON

and OFF depending on the "H" or "L" output signal. When using them, pull up to the positive power or pull down to 0 V. The complementary

output allows flow-in or flow-out of the output current and thus the rising and falling speeds of signals are fast. This allows a long cable

distance. They can be connected to open-collector input devices (NPN, PNP).

[RT4CY]

Hi JTMX39,

The PCI-6220 would work with either the NPN (open-collector) or the PNP (line-driver) encoder.  One concern is the output current of the NPN encoder has a max of 35 mA, which exceeds the sinking current limit of the PCI-6220 (16 mA).  However, this should not be a problem because the input impedance of the PFI lines is 20 kOhm minimum.  Applying Ohm's Law, the current input should be as follows.

I = {5 V / (20 kOhm + 2 kOhm)} = 0.227 mA

The Complementary Output (Push-Pull) encoder will not work with the PCI-6220 because we are exceeding the maximum input voltage of the counters on the device (5 V). 

For your information, I have provided some informative KnowledgeBase articles as well as the NI 622x manual below.

KnowledgeBase 3JAF2BVB: What is the Difference Between a Line Driver, Open Collector, and Push-Pull ...
KnowledgeBase 2WO9LA59: Can I Connect Both PNP and NPN Signals to a National Instruments DAQ Board?
Developer Zone Tutorial: Quadrature Encoder Measurements: How-To Guide
NI 622x Specifications

Let me know if I can be of further help.

Message Edited by RT4CY on 09-25-2009 10:54 AM

[JTMX39]

Thank you Ron for the information. I have looked over the links and have a better understanding of the encoders. I still have a question on why the Complementary Output will not work. I understand the PCI-6220 will only take 5 Volts max. Since the Complementary takes (12-24VDC) does that mean it will output 12-24VDC when it is high? I see it said 2V max on low. Thanks again! I don't want to buy the wrong one.

[RT4CY]

Hello JTMX39,

Can you provide a link to the data sheet for the Complementary Output encoder?  Thank you.

[JTMX39]

Page 5 shows the circuits.

http://www.omron247.com/doc/pdfcatal.nsf/BAFEAF32CD168AC486256DC000657FED/$FILE/D05E6C31003.pdf

After talking to Omron & NI it sounds like the Line Driver is the way to go.

[JTMX39 · Accepted solution]

I purchased the Line Driver type from Encoder Products Company and it works great!