A pull up resistor is used to "pull" the logic high voltage level up to the level of the operating voltage. This is useful when the output of the Open Collector is not reaching the voltage level needed to indicate a logic high signal or when noise is present on the signal line. When a logic high signal is present its voltage level will be approx. that of the operating voltage for an open circuit. The difference is due to the voltage drop across the pull-up resistor. This is not necessarily true if the load is referenced to ground.

Quadrature output refers to the fact that the signals A and B are separated by 90 degrees of phase shift with A leading B or B leading A depending on the direction of rotation. It does not mean that the output will be 4 times the amount of the Pulses Per Revolution of the encoder. The fact that the signals are 90 degrees out of phase enables the controller to determine the direction that the encoder is spinning. You must use both the A and B signal to have a quadrature output and to get X2 or X4 logic. (see What is the difference between Quadrature and x4 Logic?)

A differential output refers to the fact that each channel has a complement channel, i.e. Channel A and Channel A not. A differential line driver is used to help increase noise immunity (see What are the A not and B not Channels used for?). A differential line driver also allows you to sink or source more current than a Totem Pole output. A differential line driver will work both with a sinking or sourcing circuit. (see What is a Sinking or Sourcing input?) It can also help in increasing the distance in which a signal is transmitted.

It very possible for our dual output encoders to have multiple PPRs. All NorthStar SlimTach encoders offer different PPRs. However, the NorthStar RimTach dual output encoders must be from the same PPR family. For example, an encoder with a 256 PPR can be paired with a 512 but not a 600.

Although stainless steel is the most common choice for corrosive environments, you can also use anodized aluminum encoders. An anodized aluminum encoder is much lighter in weight than stainless steel, and offers benefits such as sulfur inertness, corrosion resistance and chemical inertness. However, it is common to paint the aluminum housing to help protect it from corrosive elements, such as salt.

Stainless steel encoders are preferred in applications that are subject to corrosive elements. For example, salt baths and wash downs are common in the Food and Beverage industry. In this case, a stainless steel encoder is most appropriate due to its ability to withstand salt water exposure over time.

The difference in single and dual output encoders is simple. A Single output encoders has one connector while a dual output encoder has two. Having a dual output encoder is like having two encoders contained in one housing. However, both outputs are electrically isolated from one another.

A unidirectional encoder, also known as a single channel encoder, is primarily used for speed sensing applications. A single channel encoder only generates one signal  as an output (signal A).