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| resources:eval:user-guides:eval-ad7441x0:tools:commissioning [14 Sep 2021 15:41] – [Case Study: Load Identification in a Temperate Control Process] Bríde Ní Riagáin | resources:eval:user-guides:eval-ad7441x0:tools:commissioning [14 Sep 2021 16:09] – second draft Bríde Ní Riagáin | ||
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| =====Commissioning made easy with AD74412R/ | =====Commissioning made easy with AD74412R/ | ||
| - | \\ During the installation stage of a process or building control system, sensors and actuators need to be connected to their respective control/ | + | ====Introduction==== |
| - | \\ By using the flexibility of the AD74412R/ | + | \\ During the installation stage of a process or building control system, sensors and actuators need to be connected to their respective control/ |
| + | \\ The Analog Devices Software Configurable I/O product family has 2 quad-channel Software Configurable | ||
| + | \\ By using the flexibility of the AD74412R/ | ||
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| ===Understanding the Instrument Characteristics=== | ===Understanding the Instrument Characteristics=== | ||
| - | \\ To begin, the characteristics of the sensors and actuators required for this process should be determined. Once the characteristics are understood, | + | \\ To begin, the characteristics of the sensors and actuators required for this process should be determined. Once the characteristics are understood, |
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| * A typical Control Valve for this process requires two channels, one to sense the position state of the valve using a voltage input channel, and one to control the actuator of the valve using a current output channel | * A typical Control Valve for this process requires two channels, one to sense the position state of the valve using a voltage input channel, and one to control the actuator of the valve using a current output channel | ||
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| ===Determining how the Channels are Configured=== | ===Determining how the Channels are Configured=== | ||
| \\ Now that the characteristics of the sensors & actuators are understood, the next step is to determine which channel is connected to which instrument. This example starts with the Control Valve as it uses 2 channels which have a “cause and effect” relationship that can be used for confirmation. The valve is controlled by a current in 4mA – 20mA range. The position sensor returns a voltage corresponding to the position of the valve. | \\ Now that the characteristics of the sensors & actuators are understood, the next step is to determine which channel is connected to which instrument. This example starts with the Control Valve as it uses 2 channels which have a “cause and effect” relationship that can be used for confirmation. The valve is controlled by a current in 4mA – 20mA range. The position sensor returns a voltage corresponding to the position of the valve. | ||
| - | \\ Start by sourcing a current (using current output mode) on a single channel while monitoring the voltage (using voltage input mode) on the other 3 channels for a correlating input signal. | + | \\ A current |
| - | \\ Figure 2 shows that when sourcing a current on Channel C, a correlating voltage input is observed on Channel D, confirming Channel C as the actuator control channel and Channel D as the position sensor channel. Confirmation of these channels is achieved in a maximum of 4 attempts. | + | \\ Figure 2 shows the response on all 4 channels |
| {{ load_confirmation_of_control_valve.png }} | {{ load_confirmation_of_control_valve.png }} | ||
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| - | While the two actuator channels have been confirmed, there is also an indication of the components on remaining channels. | + | To confirm which channel is connected to the RTD, the remaining channels (A & B) are configured |
| {{ load_confirmation_of_rtd.png }} | {{ load_confirmation_of_rtd.png }} | ||
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| - | By a process of elimination, | + | By a process of elimination, |
| - | * If the emergency button is pushed, the switch appears as an open circuit. An open-circuit alert will have been observed while determining control valve channels using Current Output mode | + | * If the emergency button is pushed, the switch appears as an open circuit. An open-circuit alert will have been observed while determining control valve channels using Current Output mode. The alert condition is asserted in the ALERT_STATUS register of the AD74412R/ |
| - | * If the emergency button is not pushed, the switch appears as a short circuit. Configure the channel in voltage output mode and check for short-circuit error alert | + | * If the emergency button is not pushed, the switch appears as a short circuit. Configure the channel in voltage output mode and check for short-circuit error alert. |
| - | \\ | + | |
| - | \\ In summary, by using simple electrical properties of the connected instruments and the on-board configuration and diagnostic tools of the AD74412R/ | + | |
| + | \\ This is an example of confirmation, | ||
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| - | ====Introduction==== | ||
| - | In the commissioning stage of building or process control and factory automation systems, sensors and actuators can often be placed large distances away from the control modules, or crowded cabling can become a tangled nest of wires. This can lead to an exhaustive exercise when confirming which sensors/ | ||
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| - | \\ The Analog Devices Software Configurable I/O product family has 2 quad-channel Software Configurable I/O parts for building and process control applications, | ||
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| - | \\ This process of sensor confirmation highlights the flexibility and value of the Software Configurable I/O parts. This flexibility makes the AD7441xR more than just an I/O circuit; its configurability makes it suitable for any customer configuration, | ||
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| - | \\ To demonstrate how the AD7441xR can be used to confirm the sensors and actuators on a channel, two hypothetical commissioning scenarios are examined below; the first examines a process control scenario for a hot water mixing tank, and the second examines a building control scenario for controlling lighting intensity with regard to room brightness and occupancy. In each of these scenarios the sensors and actuators required for control are identified, followed by an examination of the electrical properties of the components to determine how those properties can be used to differentiate the components so that they can be correctly identified on the relevant channel. | ||
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| - | \\ The examples are of confirmation, | ||
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| - | \\ ====Case Study: Temperature Control Process==== | ||
| - | This example scenario focuses on a process in which temperature control of a water mixing tank is required. This is a common process in production lines where precise water temperatures are required in large quantities. | ||
| - | As shown in the diagram in Figure 1, a water tank has a cold and hot water input. A valve placed on the hot water input pipe from a boiler adjusts the input flow of hot water to control the tank temperature. A temperature probe is placed in the tank to monitor the water temperature. An emergency stop button is also placed near the tank to shut off input flow in case of an emergency. All components are connected to the control module for the process, which uses an AD7441xR Software Configurable I/O as an interface. | ||
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| - | {{ Temp Control Process.png }} | ||
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| - | \\ Figure 1: Temperature Control Process Diagram | ||
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| - | \\ ===Components Required=== | ||
| - | Three components are required for the process outlined above; an electrically controlled ball valve to set the input flow rate of hot water, an RTD temperature probe sensor and an emergency stop button. For this example, a generic current-controlled control ball valve, a Pt100 Resistance Temperature Detector (RTD) and a generic latching emergency stop button are used. The control ball valve requires two channels, one to control the position of the valve by current output, and another to sense the current position of the valve by voltage input. The Pt100 RTD is suitable for the range of temperatures of this process, as Pt100 RTD’s are suitable for the -200°C to 600°C range, and have a resistance of 100Ω at 0°C. | ||
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| - | ===Confirming Channel Connections=== | ||
| - | In this example, the determination process is started by determining the characteristics of the sensors and actuators that will allow them to be differentiated. | ||
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| - | \\ The control ball valve uses two channels. One channel is used to control the actuator position by current output, and another is used to sense the current position of the actuator by voltage input. This is exploited to determine which channels are connected to the actuator and sensor due to the relationship between the two. Given the configuration flexibility of the AD7441xR Software Configurable I/O, current output and voltage input can be configured on any channel. By sending current output control signals to one channel and monitoring the other 3 channels to observe a correlating voltage input, the channels which are being used for the control ball valve can be determined in a maximum of 4 attempts. | ||
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| - | \\ The Temperature Probe is a Resistance Temperature Detector, which is simply a resistor whose resistance changes linearly with temperature in a defined range. Thus, the channel being used for the RTD can be confirmed in two ways. The first involves using knowledge of the expected value of resistance for the RTD. Since this is a water-based process, the temperature range limits are 0°C to 100°C. A Pt100 RTD has a resistance of 100Ω at 0°C and approximately 138Ω at 100°C. A resistance measurement can be made on all 4 channels to scan for a resistive value that falls within the expected range of 100-138Ω, which will indicate with reasonable certainty that the RTD is on a given channel. The second method of confirming the channel of the RTD is to exploit the heating effect of a resistor. Since the RTD is a resistor, start by recording the resistance of the RTD, then sourcing a small amount of current to the RTD for a short time. This should be enough to induce a small heating effect in the resistor without being significant enough to damage the device. After this, re-measure the resistance, which due to the heating effect will have increased, confirming that this channel is the RTD. Care should be taken when using this method to limit the current excitation to prevent damage to any connected components. | ||
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| - | \\ The Emergency Stop Button is simply a push-to-break latching button, which will electrically present as either an open-circuit or short-circuit. The AD7441xR is equipped with advanced on-board diagnostics, | ||
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| - | \\ ====Case Study: Building Control System==== | ||
| - | This example scenario focuses on a building control system in which the lighting in the building is controlled based on room brightness and occupancy in order to reduce energy usage (see demo system in Figure 2). This is a common scenario in building control applications, | ||
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| - | {{ building control demo.png }} | ||
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| - | \\ Figure 1: Building Control Demonstration | ||
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| - | ===Components Required=== | ||
| - | As detailed above, the required components for this scenario include an occupancy sensor, a light intensity sensor, a light intensity control and a temperature sensor. These components are all present on the system demo shown in Figure 2. A PIR (Passive Infra-Red) occupancy sensor is used to sense motion by detecting changes in the ambient levels of infrared radiation, which is disturbed when a warm body such as a human passes by. The PIR sensor uses a refracting lens to allow it to monitor a large area for such changes, allowing it to accurately detect if a room is occupied or not. The sensor acts as a digital input, pulsing the voltage high when motion is detected. This is used with the Digital Input function of the AD7441xR. The light intensity sensor measures luminosity in the range detectable by the human eye, allowing for an accurate indication of how bright the environment is. It returns a 4-20mA Current Input measurement of the light intensity within a given range, with the default being 0 to 1 kLux which is within the intensity range of most buildings. The LED Dimming Controller is a voltage controlled analog dimmer, which uses a 0-10V analog input to control the dimming level of the LED strips attached to it. This allows for full control of the light intensity in the range of the lighting fixtures in an environment being completely off or completely on. The temperature sensor is a Pt100 Resistance Temperature Detector (RTD), electrically similar to the RTD temperature probe used in the previous scenario. A Pt100 RTD has a resistance of 100Ω at 0°C and approximately 138Ω at 100°C. | ||
| - | Aside from the RTD Temperature Sensor, all other components are externally powered. | ||
| - | \\ Note that the system demo above uses the AD74412R Software Configurable I/O evaluation board. | ||
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| - | \\ ===Confirming Channel Connections=== | ||
| - | The components used in this scenario are similar in ways to the previous process control scenario – the RTD measures temperature by a variable resistance, the PIR occupancy sensor returns a true or false digital input, the LED dimming controller and light intensity sensor form a sensor and actuator pair with a cause-and-effect relationship similar to the control ball valve in the previous example. However, in this scenario, the electrical components are not as robust, and are more likely to be damaged if the same approach from the process control scenario (of sending control signals on all channels to observe the changing response as a starting point for determining channels) is used. In this scenario the opposite approach is used, by using characteristic differences to determine all other channels and using the cause-and-effect observation to provide final confirmation. | ||
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| - | \\ The Pt100 RTD temperature sensor can be determined by using the expected resistance value for a building control application. A Pt100 RTD has a resistance of 100Ω at 0°C and approximately 138Ω at 100°C, which changes linearly throughout this range. The resistance in a comfortable building environment can be expected to be in the range of 104Ω - 116Ω (10°C to 40°C). Since the AD7441xR enables RTD measurements on any channel, a resistance measurement is done on all 4 channels to find a resistive value that falls within the expected range, which will indicate with reasonable certainty that the RTD is on a given channel. | ||
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| - | \\ The PIR occupancy sensor is a digital input which pulses a high voltage (digital “1”, or true) if the sensor detects motion in the environment. This type of sensor uses 3.3V logic and is externally powered, so a true condition returns a 3.3V voltage input, which can used to differentiate the PIR occupancy sensor from the RTD, which returns no voltage input, and the LED dimming controller and light intensity sensor which operate at 10V. | ||
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| - | \\ The Light Intensity Sensor is an analog input sensor that returns a 4-20mA signal dependent on light intensity in the environment. At least 4mA of current is measured from the sensor, even in the case that the room is in complete darkness. The AD7441x current input mode can be used to detect a current in the 4-20mA range and this measurement differentiates the light intensity sensor. | ||
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| - | \\ ====Conclusion==== | + | ====Conclusion==== |
| - | Using the host of configuration options | + | By using simple electrical properties |
| - | This process highlights the flexibility and value of the AD7441xR Software Configurable I/O. The availability of various excitation & measurement functions on each channel enables this capability | + | \\ This process highlights the flexibility and value of the AD7441xR Software Configurable I/O parts and can dramatically reduce the installation time and avoid mis-wire problems seen during installation, saving significant time and expense. |
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resources/eval/user-guides/eval-ad7441x0/tools/commissioning.txt · Last modified: 14 Sep 2021 16:10 by Bríde Ní Riagáin