An output block is the logical image or memory map of a command, and describes its properties. Within the program, the Present Value is made available to the block as a program value. The block converts the program value and transmits the raw data to the physical I/O.
If an output is deleted from an existing system in the course of a modification, the I/O module will retain the last valid value which it received from the system. You can return the I/O channel to the default status by switching the power off and on again. This problem can be avoided by performing a complete download.
Binary Output (BO)
The binary output block is the logical image, or memory map, of a binary switch command and describes its properties. Within the program it is made available to the block as a program value, and its parameters are set via the "Polarity" pin. The block converts this program value and transfers the raw data to the physical I/O, where it is converted into a digital signal, e.g., which drives the field device via a contact.
The following functions are integrated in the block:
- Evaluation of the priority array [PrioArr]
- Inversion of the switch value and the feedback value (Polarity of feedback [Bop])
- Interruption of the output signal [OoServ]
- Feedback monitoring (OFFNORMAL alarm)
- Reliability monitoring [Rlb] (FAULT alarm)
- Change of state messages (events / system events)
- Configurable switch types (Normal, Trigger, Pushbutton, Pushbutton with delay)
- Runtimes and monitoring periods
- Switch-command delays
- Process monitoring [StaFlg]
- Runtime totalization and maintenance messages
Feedback monitoring for dampers with one end switch
To monitor the damper position of dampers with one end switch, the switch position must be set by defining the polarity of the feedback signal [Bop].
OPEN end switch -> Feedback polarity [FbPol] set to NORMAL
CLOSED end switch -> Feedback polarity [FbPol] set to INVERTED
Feedback monitoring for dampers with two end switches
The monitoring of dampers with two feedback signals (Open/Closed) is implemented via the address string of the Feedback Address [FbAddr]. The first address in the string must be that of the end switch which indicates that the damper is closed. The end switch indicating that the damper is open is set in the second part of the address string.
Example with PX modular:
P= M1.K1; M2.K2 (D20)
- 1. 1st address: Damper-CLOSED switch
- 2. 2nd address: Damper-OPEN switch
- Feedback polarity [FbPol] NORMAL
M1.K1 = True; M2.K2 = False -> Feedback value: Closed
M1.K1 = False; M2.K2 = True -> Feedback value: Open
When the damper is being driven to the OPEN or CLOSED position, this transient state [TraSta] is displayed. If the preset monitoring time is exceeded, an alarm is initiated. If the damper fails to reach an end position, the alarm is reset again after the monitoring time has expired. There is otherwise no automatic block reaction, that is, if a switch response in the plant is required as a reaction to this alarm, this response must be programmed in CFC via the disturbance output [Dstb].
Multistate Output (MO)
The multistate output is the logical memory map of a multi-state switching command, and describes its properties. Within the program, the current value is made available as a program value to the block and transmitted after conversion into raw-data format to the physical I/Os. Here the raw data is converted into a digital signal, e.g., which drives the field device via a contact. It is also possible to connect a multistate feedback signal, which is used for alarm evaluation.
The following functions are integrated in the block:
- Evaluation of the priority array [PrioArr]
- Interruption of the output signal [OoServ]
- Feedback monitoring (OFFNORMAL alarm)
- Reliability monitoring [Rlb] (FAULT alarm)
- Change of state messages (events / system events)
- Configurable switch type (Normal, Motor, Trigger)
- Runtimes and monitoring periods
- Hardware mapping (refer to Section 0)
- Runtime totalization and maintenance messages
- Process monitoring [StaFlg]
Analog Output (AO)
The analog output is the logical image, or memory map, of an analog control command and describes its properties. Within the program, the Present Value is made available to the block as a program value. The block converts the program value and transfers the raw data to the physical I/O, where it is converted into a 0…10 V signal, e.g., to drive a field device.
The following functions are integrated in the block:
- Evaluation of the priority array [PrioArr]
- Interruption of the output signal [OoServ]
- Conversion of the process value and feedback signal with slope [Slpe] and
- intercept [Icpt]
- Configurable switch type (Normal or Trigger)
- Limit value monitoring (OFFNORMAL alarm)
- Deviation monitoring
- Reliability monitoring [Rlb] (FAULT alarm)
- Change of state messages (events / system events)
- Process monitoring [StaFlg]
The value [PrVal] from the program is converted into the physical positioning value by use of a conversion curve. This present value is then available at [PrVal] for further processing in the program while at the same time, the raw data is transmitted to the associated I/O system, where it is converted into an electrical signal to drive the field device.
The conversion curve is a linear function which takes the following form:
Raw Value [RwVal] = [PrVal] * Slope + Intercept
The values for slope [Slpe] and intercept [Icpt] must be defined specifically for the application concerned in accordance with the I/O system in use and the signal type.
For slope [Slpe] and intercept [Icpt] values for SBT products, see Slope [Slpe] and Intercept [Icpt].