This unique addition to the Phoenix Contact signal conditioning line utilizes 915-928 MHz ISM band spread spectrum frequency hopping technology to guarantee a license free, interference free link between remote devices and the control room. Costly cable and conduit runs on new projects, or retrofitting of existing systems, are eliminated and replaced with a maintenance free, reliable and versatile wireless solution.
Common applications include monitoring/control of pressure, level, temperature, flow, switching and alarms in situations where cable and conduit are either impossible or too costly to install, for example, retrieving pressure readings from a device on the other side of a railway track. The modules are available as a transmitter/receiver pair and come factory programmed, calibrated and tested as a set. Further switch configuration and programming are not required. Each set is given a unique address at the factory enabling multiple MCR-RAD systems to work independently in the same area without interference. The transmitter and receiver are powered separately by a 12-30 Vdc source (power supply, battery, solar etc). Quick and easy to install, the process signals are simply wired to the input terminals of the transmitter and output via wires connected to the receiver. No wiring is required in between. Typical in-plant range is 200 – 300 meters with no line-of-sight, much farther with outdoor
applications. Both the transmitter and receiver are DIN-rail mountable and with their dimensions of 102 mm (length) x 114.5 mm (height) x 17.5 mm (width) they offer a small wireless solution for every control cabinet. The MCR-RAD provides LED indicators for digital input/output signal status at both radios and radio link status at receiver.
What is Frequency Hopping Spread Spectrum Technology?
Prior to its introduction to Industrial, Scientific and Medical (ISM) use in 1987, this technology was used by the military for battlefield communications and weapons control due to its extreme tolerance of interference, and the difficulties it presented to those wishing to jam or intercept it. The key elements for the success of these radios are:
a) their ability to frequency hop,
b) their use of powerful narrowband signals (highest transmit power available under FCC guidelines), and
c) their reliance on the redundant nature of the data being sent. Broadcasting within the 915-928 MHz band, MCR-RAD radios transmit the status of their inputs on one frequency, then hop to transmit again on a different frequency. Hopping approximately every 20 milliseconds, the status of their inputs is updated 50 times per second in an interference free environment. In an industrial application, where interference is encountered from a variety of sources, EMI, motors, arc welders, etc., some hops will be affected. Anticipating interference the MCR-RAD receivers’ error-check the data packet on every hop. When corrupted packets are received they discard the bad data and, hopping in synch with their transmitters, they look for the next clean update, which is then output. Since interference is encountered in most industrial applications it is assumed that all updates will not get through. Even so, if only 50 to 75% of the packets make it through unscathed this is more than adequate to update pressure, level, temperature, flow, ON/OFF and alarm.
MCR-RAD-T Transmitter
Diagnostics
MCR-RAD-T-DIN:
- RF LED is solid green when unit is transmitting normally.
- LEDs 1 and 2 show status of digital inputs 1 and 2. Solid green = ON.
MCR-RAD-T-DC: (optional weatherproof DC system)
- Green LED on top of unit is solid green when unit is transmitting normally.
- This unit does not have LEDs for digital inputs.
MCR-RAD-T-AC: (optional weatherproof AC system)
- Green LED on top of unit is solid green when unit is transmitting normally.
- This unit does not have LEDs for digital inputs.
MCR-RAD-R-DIN Receiver
Diagnostics
- The receiver features an RF link relay (alarm) that closes when RF link is established and locked with the transmitter. This provides solid indication (to PLC or other monitoring equipment) of the wireless link.
- RF link LED blinks once every 2 seconds when receiver is ON but transmitter is either OFF, or out of range.
- RF link LED continually blinks very rapidly when marginal signal is being received. This is an indication that one or both radios should have their antennas moved to an area where they will get better reception.
- RF link LED blinks occasionally (random). This is an indication that interference is being encountered on some hops. This will not affect the performance of the radio and the installation should be considered successful.
- RF LED is solid when an extremely secure link is established.
- LEDs 1 and 2 show status of digital outputs 1 and
2. Solid green = ON.
Default Output Status
As default the 4-20 mA analog signal on the receiver is designed to maintain last state. The default status of the two digital outputs is to also maintain last state. For diagnostics and alarm purposes the RF link output can be used to drop the 4-20 mA to 0 mA if the analog output is wired through the RF link contact (or with an external relay) - this gives you 0 mA when the link is lost. The RF link relay can be used to turn ON/OFF one or both of the digital outputs by wiring them through the RF link contact (or an external relay connected to it) - this gives you options for the digital outputs when link is lost.
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