 The 905U-K wireless I/O module is an economical solution for the remote monitoring of process signals. The 905U-K connects to discrete, pulse or analog signals from process transducers, and transmits these signal values by radio. The 905U-K is suitable for alarm or metering applications, as well as general plant monitoring.
The 905U-K has an internal 900MHz frequency-hopping radio transmitter which operates on a license-free radio band. The 905U-K has an operating range of more than 20 miles (30km). It is suitable for monitoring in utility industries such as electricity, water and gas; and is also a cost effective solution for short range applications in factories and plants.
Mode of Operation
The 905U-K is compatible with the 905U range of wireless I/O products# - 905U units may be used to output the process signals, or act as a wireless interface connected to a PLC, DCS or PC. The 905U-K transmits the value of its input signals whenever the signal changes, or after a pre-configured update time. Each transmission message includes error-checking to confirm the validity of the message. The 905U-K can be configured to repeat the transmission several times to ensure that the transmission is received correctly. The input signal is output at a 905U unit either as an identical signal or across a serial data link (RS232 or RS485).
905U units may also be used as repeaters to extend the radio range of the 905U-K - up to five intermediate 905U modules may be used as repeaters in any radio path.
More than 10,000 905U-K units may operate together in a single system.
#refer to 905U product literature
Extremely Low Power Consumption
The power consumption of the 905U-K is very low as it conserves power by reverting to "sleep" mode between measurements of the input signals and transmissions.
The 905U-K can be powered from a 6 - 30 VDC supply. It can also be powered from one or more ELPRO BU-5 battery packs without any other power source. Each battery pack can power the 905U-K for over a year, depending on input signal configuration. The 905U-K unit provides an internal alarm on low supply voltage - this alarm can be transmitted by radio.
Weatherproof NEMA4 Enclosure
The 905U-K is enclosed in a heavy duty painted aluminum enclosure, weather-proofed to NEMA 4. Signal and power connections to the unit are made via a weatherproof connector.
Because of its battery power supply and weatherproof case, the final installed cost of the 905U-K radio telemetry module is very low, making it a cost effective solution for even simple plant monitoring applications.
Inputs
The 905U-K unit can connect to two discrete or pulse signals and one analog signal, and will transmit the value of an input when the value changes. The input value is also transmitted if the signal has not changed within a user-configured update time (configurable 10 sec to 7 days). Pulse signals use the same input connection as discrete inputs.
Alarm and Status Signals
The 905U-K can connect to two discrete inputs such as alarm or status signals which are voltage free contacts or TTL 5V signals. Whenever the discrete signal changes (off to on, or on to off) the 905U-K will interrupt its sleep mode and transmit the signal value. The 905U-K will also transmit the input values after a pre-configured update time. There are different update times for when the discrete signal is "on" or "off". For example, an alarm input can update once per day when it is inactive, but update every minute when it is active. This feature allows a large number of 905U-K units to share the same radio channel.
As well as the two external discrete inputs, there are two internal discrete "inputs" - low battery voltage and analog setpoint status.
Pulse Signals
The 905U-K will accept two pulse signals suitable for metering applications. The 905U-K calculates both totalized pulse count and pulse rate. The totalized count is a 32 bit count (2 x 16 bit registers) and is transmitted whenever the count has changed by a pre-configured amount and also after its update time. By transmitting the totalized pulse count, the 905U-K ensures that individual pulses are not lost, Should a radio transmission not be successful, the pulse count is still held in the 905U-K, and totalized value will be updated on the next transmission.
The 905U-K can be configured for use with a quadrature or incremental shaft-encoder, where the two pulse inputs operate on a single up-down counter.
The pulse rate is treated as an internal analog input, and transmitted when the rate changes and after its configured update time. The 905U-K can accept a pulse signal up to 10 KHz.
Analog Signals
The 905U-K model has one analog input (selectable 4-20 mA or 0-10V). The analog signal may be externally or loop powered; the 905U-K generates a 24VDC loop supply. During sleep mode, the loop supply is switched off. After a user-configured sample period, the analog loop supply is activated, and the analog measurement is taken. A warm-up time may be configured to allow the analog loop to stabilize before the measurement is taken. If the sample period is set to zero, then the 905U-K does not revert to sleep mode, and it will continually measure the analog signal (note that this is not suitable when used with the BU-5 battery pack). The analog measurement has 12 bit resolution. After the analog measurement is taken, the 905U-K will transmit its value if it has changed since the last measurement. A sensitivity value is configured to determine the minimum change to cause a transmission. The analog value is also transmitted on the update time.
Configurable setpoint values may be used to generate an internal alarm status which can also be transmitted. The setpoint status is treated as another discrete input. Both the analog value and the setpoint status may be transmitted. |
