楼宇第10次课 CHAPTER 4 Electronic Control Fundamentals 电气及其自动化自动化专业选修课 楼宇自动化(英文版教学课件).pptVIP

Transmitter: A device that converts a sensor signal to an input signal usable by a controller or display device. function of the relative humidity, causing a change in resistance of the sensor. An electronic controller connected to this sensor detects the changes in resistance which it can use to provide control of relative humidity. * * CHAPTER 4 Electronic Control Fundamentals INTRODUCTION This section provides information about electronic control systems used to control HVAC equipment. An electronic control system comprises a sensor, controller, and final control element. The sensors used in electronic control systems are simple, low mass devices that provide stable, wide range, linear, and fast response. The electronic controller is a solid-state device that provides control over a discrete portion of the sensor range and generates an amplified correction signal to control the final control element. Features of electronic control systems include: — Controllers can be remotely located from sensors and actuators. — Controllers can accept a variety of inputs. — Remote adjustments for multiple controls can be located together, even though sensors and actuators are not. — Electronic control systems can accommodate complex control and override schemes. — Universal type outputs can interface to many different actuators. — Display meters indicate input or output values. The sensors and output devices (e.g., actuators, relays) used for electronic control systems are usually the same ones used on microprocessor-based systems. The distinction between electronic control systems and microprocessor-based systems is in the handling of the input signals. In an electronic control system, the analog sensor signal is amplified, then compared to a setpoint or override signal through voltage or current comparison and control circuits. In a microprocessor-based system, the sensor input is converted to a digital form, where discrete instructions (algorithms