Bus System Products for On/Off Batching
(As seen at Chem Show '97) StoneL's AS-interface (Actuator Sensor interface) is a standardized protocol well suited to On/Off batching processing applications. Fully field proven, the system is easy to install, highly reliable, and readily interfaces with other bus networks and computer systems. The system communicates serially using one pair of wires and both power and signal can use the same pair of wires. The system has one master and up to 31 slaves (field devices) on a single network. The network is deterministic and, with 31 field devices connected, has a maximum cycle time of 5 ms. The network can be up to 100 m long with provision for 2 repeaters for a total of 300 meters or 984 feet.
System Components
A typical system consists of a master/gateway, power supply, field devices (attached to the valve actuator), and simple T connections to connect each field device to the bus. Repeaters could also be used if ommunication was desired beyond 100 m. Some interface software may also be required to tie the master to the host control software. For ease of installation, a handheld programmer is recommended to program a unique address into each field device before it is placed on the bus.
Masters/Gateways
The master is the interface between the host computer and the field device. It controls the communications on the network and provides error detection and correction to the network and error reporting to the host. Several different versions of AS-i masters are available.
Communication Modules (Field Devices)
The field devices provide the interface between the network and the sensors and actuators. Each field device can have 2 inputs and 2 outputs or 4 inputs or 4 outputs. The communication modules have 2 integrated solid state inputs and 2 outputs designed to switch solenoid valves up to 4 W.
Power Supply
Because power is supplied with the signal on the same pair of wires, a special AS-i power supply is required. A regular off-the-shelf supply will not work.
StoneL Valve Communications, One StoneL Dr., Fergus Falls, MN 56537. Tel: 800-843-7866.