Shaft encoder

Flow meters have traditionally been classified as either electrical or mechanical depending on the nature of the output signal, power requirements, or both. However, improvement in electrical transducer technology has blurred the distinction between these categories. Many flow meters previously classified as mechanical are now used with electrical transducers. Some common examples are the electrical shaft encoders on positive displacement meters, the electrical (strain) sensing of differential pressure, and the ultrasonic sensing of weir or flume levels. 

Pulse Inputs Where the sensor within the measurement device is digital in nature, analog-to-digital conversion can be avoided. For rotational devices, the rotational element can be outfitted with a shaft encoder that generates a known number of pulses per revolution. The digital system can process such inputs in either of the following ways ... 

A DC motor is feedback-controlled by a current sub-control loop and a primary speed control loop. In order to close the control loop, the actual current value is fed back to the current control loop and a speed signal to the speed control loop. While current is measured in the power converter, a shaft encoder on the motor is required for speed signal feedback. Either a tacho-generator or a digital encoder is used as a speed transmitter. If speed measurement accuracy is not very important, the speed feedback can be measured via armature voltage. In this case, this measurement can also be done within the power converter. Static control accuracy reaches... 

Figure 17.9 Shaft encoder with insulated bearings...

Today, infrared LEDs are used in a wide variety of applications, where they are typically paired with photodetectors. Infrared flux emitted by an LED source is transmitted a distance ranging from a few millimeters to many meters, and at the receiving end a photodiode or phototransistor detects the flux and converts it to an electrical signal. Silicon devices are most commonly used to detect the light emitted by Al Gai-xAs DH LEDs. Photodetectors made from In Gai-xAs are used with Ga Ini- AsyPi-y LEDs. Such emitter-detector pairs are used for the remote control of televisions and other consumer electronic products. Other applications for infrared LED-detector devices include intrusion alarms, blood gas analyzers, bar code readers, limit switches, and shaft encoders. 

A binary shaft encoder, which produces 100 pulses per revolution of its input shaft, is geared to the lead screw by means of a timing belt. This shaft encoder supplies its output to a beam switching counter which stores the pulses and presents the total accumulated number of pulses to the digital printer on command. With a 50-ml syringe one pulse or count is approximately... 

Shaft Encoding. LDV measurements in stirred vessels are typically combined with shaft encoding so that the velocity can be analyzed either as a long-time... 

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