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UNIVERSAL RADIO FREQUENCY
INTERROGATOR (URFI) USER’S MANUAL
(PRELIMINARY VERSION)
AMERICAN METER COMPANY
AUTOMATED SYSTEMS BUSINESS UNIT
107 ERSKINE LANE
SCOTT DEPOT, WEST VIRGINIA 25560
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Overview
The Universal Radio Frequency Interrogator® (URFI®) is a portable radio transceiver
used in conjunction with any customer-supplied handheld or portable computer to
provide remote meter reading of Trace® system transponders. The Trace system is
designed to convert the mechanical index reading of a utility meter to a duplicate
electronic register reading. This electronic register reading is transmitted via radio
frequency (RF) signals to the URFI. The URFI reads each transponder b y means of an
RF interrogation that consists of a unique serial number along with a command
requesting the contents of the electronic register. The meter reading route data, which
contains the street address and serial number of each transponder that is to be read, is
stored by the computer, as is the actual meter reading following a successful
interrogation; no data is stored in the URFI itself.
The URFI is controlled by a number of commands sent from the computer. Primary
functions controlled by the computer’s route-reading application are: initiation of
interrogation; setting of receiver channel; and setting of power up/down modes.
A typical interrogation sequence consists of the following.
1. The computer powers up the URFI and the URFI performs its initialization routine,
which includes programming the receiver and transmitter frequency synthesizers.
2. The computer sends the serial number of the transponder to be interrogated to the
URFI through a serial port connection.
3. The URFI transmits a synchronization data pattern followed by the transponder serial
number. This transmission is approximately 1.5 seconds in length.
4. A transponder ‘wakes up’ at some point during the URFI’s synchronization data
pattern transmission, hears the serial number and replies with the meter reading data
if the serial number heard matches its own. Otherwise, the transponder goes back to
sleep.
5. The URFI receiver listens for the transponder reply. If no valid data is d etected, the
receiver scans a range of adjacent channels for valid data. In this way, the receiver
finds a drifted transponder signal, and the URFI sends the transponder channel to the
computer; the URFI then re-interrogates with its receiver set to the new channel.
6. When the URFI receiver receives a valid transponder reading, this data is passed from
the URFI to the computer for storage.
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URFI System Components
Transmitter
451.35MHz,
AM
RF Board
Digital
Board
URFI
Receiver
415MHz,
FSK
PC Device
(Handheld, VID, Laptop)
Serial
Port
Battery
(12VDC, 2.0AH)
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Connections
The URFI has four ports which need to be connected to peripheral devices.
Transmit BNC connector.
1.
side of the front face of the unit. This shall be connected to an antenna having a
nominal 50 Ohm impedance at 451 MHz. Three antennas are available from
American Meter: 1) roof mount antenna for mobile use; 2) right angle 5/8 wavelength
antenna; and 3) right angle 1/4 wavelength antenna.
Receive BNC connector.
2.
side of the front face of the unit. This shall be connected to an antenna having a
nominal 50 Ohm impedance at 415 MHz. Three antennas are available from
American Meter: 1) roof mount antenna for mobile use; 2) right angle 5/8 wavelength
antenna; and 3) right angle 1/4 wavelength antenna.
Serial port connector.
3.
connected to the appropriate serial port (COM port) of the user’s computer via a serial
cable.
Power connector.
4.
connected to the right angle plug of the power cord supplied with the unit. The other
end of the power cord shall be connected to the supplied 12VDC battery for portable
use or directly to the cigarette lighter receptacle of an automobile for mobile use.
The DC power connector, located on the bottom of the unit, is
The transmit BNC connector is the connector on the left
The receive BNC connector is the connector on the right
The nine-pin serial port, located on the bottom of the unit, is
Indicators
Two light emitting diodes (LEDs) are located on the top end of the unit.
The green LED indicates that the URFI is powered on. For the URFI to be powered, it
must have a sufficient DC supply and a logic level ‘high’ on the DTR pin (pin 4) of the
serial port, which is supplied by the computer.
The red LED indicates that the URFI is in the transmit mode.
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Specifications
Power source:
Transmit frequency:
Transmit power:
Transmit modulation:
Receive frequency:
Receive bandwidth:
Receive sensitivity:
Operating temperature:
Storage temperature:
12 VDC vehicle power or sealed, rechargeable 12VDC lead
acid battery
450 – 460 MHz (determined by customer’s FCC licensed
frequency)
2 Watts average power into 50 Ohms at antenna connector
(factory set)
Double-sideband, large carrier AM; 85% nominal
modulation index
412 – 416 MHz, wideband FSK
200 kHz
-100dBm typ. (50 Ohm source at antenna connector)
-30ºC to +60ºC (-22ºF to +140ºF)
-40ºC to +85ºC (-40ºF to +185ºF)
Size:
Weight:
FCC compliance:
6.25 x 4.25 x 2.00 inches (does not include connector
protrusion)
2 lbs. (approximate)
Part 90 (FCC ID: G8JURF01)
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