Excitation Voltage

Some sensors require an excitation voltage to feed the Wheatstone bridge and generate their output signal as a ratio of the input excitation voltage. Thus, you need to establish if your DAQ or PLC can support the sensor’s input voltage or excitation voltage requirements. Simply put, an unstable excitation voltage input leads to an unstable sensor output. In case you need an amplifier module for PLC or DAQ and they do not provide a stable input excitation voltage, the amplifier will be the excitation voltage source to ensure the sensor provides a reliable and consistent output signal.

Filtering

Analog sensor signals are susceptible to electrical noise and/or residual ripple voltage, which can distort or skew measurements. Noise needs to be filtered out before you can capture an accurate signal. DAQs and PLCs designed to interface directly with full-bridge sensors will include pass band and other forms of signal conditioning and filtration. In a low noise signal conditioner, electronic filters eliminate some effects on accuracy by removing electrical noise and ripple effect above and below the analog sensor’s signal range, resulting in a low signal-to-noise ratio.

Amplification

Sensors can output a signal in the nanovolt through millivolt range. When your DAQ or PLC is limited to measuring volts, you will need an amplifier to convert millivolts to a larger signal. Some PLCs and DAQs come with built-in amplification; others will require an external amplifier. What if your existing DAQ or PLC does not provide built-in amplification, signal conditioning, and a stable power source for sensor excitation? In that case, you will need an amplifier to fill in the shortfalls in your instrumentation.

USB520 Features

• Supports Encoder Input: Quadrature Leading and Lagging Pulse
• USB 2.0 Communication Link;
• USB Bus-Powered (5V);
• Input/Output Short Circuit Protection;
• Streaming ASCII Output;
• Offered with DLL/Mac Dynamic Library;
• CE Approved Class A (required for Medical and Aerospace applications);
• Industrial metallic enclosure;
• Integrated DIN rail mount;
• Supports, VDC, mA, mV and TTL type input.

Dimensions

Specifications

What is an Incremental Encoder?

An Incremental encoder is an electro-mechanical device that converts the angular motion or relative position of a shaft into digital or pulse signals employing an optical disk. Incremental encoders are commonly used in rotary encoders.

This device consists of a rotating disk, a light-emitting source, and light-receiving elements (photosensor). The disk, which is mounted on the rotating shaft, has patterns of opaque and transparent sectors coded into the disk. As the disk rotates, these patterns block the light emitted onto the photodetector, generating a digital or pulse signal output, also known as quadrature pulse signal.

Incremental encoders provide rotational or angular speed. They can measure the change in position, but not the absolute position of the shaft. Since there are few constructive elements involved, it is a relatively simple and inexpensive transducer.

Commonly, the incremental encoder uses two output channels (A and B) to detect angular position. Using two code tracks with sectors positioned 90° out of phase, the two output channels of the quadrature encoder indicate both position and direction of rotation. If A leads B, for example, the disk is rotating in a clockwise direction (i.e. quadrature leading pulse). If B leads A, then the disk is rotating in a counter-clockwise direction (i.e. quadrature lagging pulse). Therefore, by monitoring both the number of pulses and the relative phase of signals A and B, you can track both the relative position and direction of rotation.

Advantages of Incremental Encoders

• Typically lower cost relative to absolute encoders;
• Good for simple pulse counting or frequency monitoring applications such as speed, direction, and position monitoring;
• Less complex than absolute encoders;
• High noise immunity.