The SDI-12 interface allows for direct connection for up to 10 x RX32-FM receivers units to a suitable data acquisition or logger unit using only a digital interface without any requirement to first convert data to an analogue value using a digital-analogue converter. A self configuring installation protocol simplifies installations. Up to 320 sensor inputs can be used on SDI-12 port.

Direct Analogue Output Connection

Using the analogue output channels available on the RX32-FM module the unit can be connected to any data acquisition system or logger unit capable of measuring 0 - 2.5V inputs but requires thermistor linearisation software when temperature compensation is required. The 16 bit DAC enables up to 65,000 levels to be identified in the signal making up the analogue output.

Wireless Option

The RX32-FM in collaboration with the VibWire-108 vibrating wire interface and NDACS 2000 MicroLogger Systems enable cable-free distributed solutions to be easily created. Most vibrating wire sensors along with thermoucples, RTD, strain gauges etc. are supported and results can be passed to data loggers and acquisition systems. Fig 5 below shows an example of a single receiver unit connected to an NDACS 6000 series data logger unit. This logger can be connected directly to the Internet for remote data reporting applications.

Operations

The RX32-FM receiver supports 32 cable free sensors or 16 x full 4 wire vibrating wire sensors when the integrated temperature sensor is being used. The sensors can be deployed at any location away from the receiver so long as the sensor signal data can be heard at a suitable level.

The RX32-FM unit is fully user configurable using the on-board keys allowing the operator to define the operating frequency, observe the signal strength and examine the analogue output levels for specified channels without having to use a data logger or acquisition system to see results.

The receiver unit monitors continually all the input channels and updates the analogue outputs with any new levels as they are received. The new sensor levels are also made available for transmission across the network ports upon the next new data request. A timeout period can be set to force the output levels for any sensor inputs not receiving new data to OV. This time out level change can be used to trigger alarm level reporting within the Keynes Controls NDACS logger units.

So long as the received signal strength is maintained above level 1 then data from the sensors can be received and decoded. For applications requiring large channel counts be they distributed or local then up to 10 x RX32-FM units can be connected together using the SDI-12 network port. All receiver outputs can be recorded within a single logger supporting the SDI-12 protocol without any requirement to undertake a single digital-analogue conversion.

See: http://keynes-controls.com/receivers/RX32-FM.htm for data sheet on this product.

See: http://www.keynes-controls.com/ndacs6008productsheet.htm for further details of the NDACS logger units.

Basic system

Demodulation

Burst packet FM

Physical Dimensions

180 x 72 x 41 mm

Power Supply

9 - 18V DC @ 30 mA Average

Operating Temp Range

-40 to +85 Deg C

Environmental Protection

Protected against the ingress of moisture, dust and high humidity

User Display

5 digit x 7 Segment display,
Frequency Meter :- accurate to 1 Hz
Voltage Meter :- accurate to 10 mV

User Menu

Using the on board keyboard to define Individual Channel configuration such as

operating frequency and unit update rate

Communication Ports

Serial Port (Optional)

RS-485 Multi-drop network - supports up to
32 RX32-FM units representing up to 1024
Cable free sensor channels detected over the
1200 m network length.

SDI-12 Interface (Optional)

Digital Serial Interface, Direct connection 1 - 10 Units. To 320 cable free sensor inputs

Analogue Output Level

16 channels @ 0 - 2.5V using 16 Bit DAC

Analogue Output Parameter

Volts

Temperature Compensation

Analogue Output

0 - 2.5 Volts

Vibrating Wire Temp Sensor

Requires thermistor linearisation

Temperature Sensors

requires sensor linearisation. (thermocouple, RTD ect..)

Receiver Interface

Frequency of Operation

FM 433 MHz UK & Europe
FM 869 MHz use in Europe and most
other countries where 434 is prohibited.

Antenna

¼ wave whip - options for high gain directional antenna for improved range or reception quality depending upon site configuration.

(Optional Repeater Units)

receiver unit depends directly upon features of the local environment that can reduce the line of site operations.

Number of Channels

256 per Operating Frequency

Maximum number VW sensor inputs

1000 (when using temperature channels )

Installation

The antenna should be installed at least 1m
above the ground and in line of sight of receiver unit.

Data Encryption

Automatic data encryption for data security

Technical Specifications

The following table summarises the operating specifications for the RX32-FM receiver unit.