Adjust TTL Low Level/Differntial Encoder

[Blee66]

Hello,

I am using a USB 6366 to try and measure the position from a differential quadrature encoder.  I do not think the USB 6366 supports differential encoder measurements, so I am trying to make single-ended measurements.  When I do this, Labview misses several encoder counts.  I checked the signal into the counter with a scope, and the low part of the square wave is floating around 0.8 to 1 V, normally a TTL grey zone.  The low part of the signal does not go to zero even if I connect the negative part of the differential signal to digital ground.

Is there a way I can adjust what the counter considers TTL low?

Is there a way to make this differential encoder measurement with my DAQ?

-Brian

[Kevin_Price]

No, you can't adjust what the counter hardware will treat as TTL low.  You're going to need to convert from differential to TTL.  There's probably a lot of different varieties of such converters around, here's one that I've used personally without any issuesl:   Encoder Interface.  

-Kevin P