What does it do?

Measures a distance (and target velocity) providing analog 4-20mA output (2 relays, digital serial port I/O and quadrature pulse output available).

Suitable in general non-contact distance, level or object intrusion detection requiring fast response time,2.5cm accuracy and narrow beam spread angle (4 degree, 75mm diameter of a lense-horn antenna). It can be used in partially obstructed applications, through narrow openings, or through microwave-transparent windows (plastic, ceramic, 6mm glass, 2.5cm wood  etc ).   Standard range is 0.5-50m with 75mm antenna (long range with larger antenna) .    Works through rain, snow, dust etc.  Tolerates dusty environment, moisture splashes on the lense and environmental temperature variations.

 How does it work?

Emitting, receiving and processing frequency modulated (FMCW) microwave signal at 77GHz (50mW). Can be re-tuned for 62 or 122GHz ISM bands.    Bult-in microprocessor performs FFT and proprietary signal analysis. 

 Interface and wiring (3 or 4 wire device):

Powered by 24V DC, 0.5A.

*  Analog output 4-20mA current loop (linked as isolated sink or 3 wire sourcing),
*  Quadrature pulse output mimicking rotary pulse encoders (5 or 24V),
*  Digital serial data port (use generic ASCII terminal program or VelTerm.exe application for WinXP)
    (Note: serial-to-USB, Bluetooth or Ethernet gateways should be used for longer distances).

 Product description - download the manual:

User Manual (pdf)

Additional software:

Text terminal emulator with graphics capability to communicate with the device, configuration and data display:
- Download  VelTermSetup.zip (full setup installation 3MB)

Firmware:
- Download  "FastRanger" firmware update (zipped .mot file, use Renesas programming tool for M16C/62P-M30626FHP)

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 Communication with the radar device and screen shots from VelTerm.exe:

Main startup screen. On prompt >  type ? <ENTER> to display the command help page from the radar device.  Click on command button (top banner) to execute following functions: 

- open parameter configuration screen

-  display results (autorepeat every 2 seconds)

- display history file (graphic plot)

- display FFT spectrum

- display FFT with autorepeat every 2 seconds

- display raw signal plot in time ("oscilloscope") 

- display frequency modulation ramp profile

Configuration Screen

History plot.  

Note: the above graph represents stability test results.  Data was logged in the sensor (Unit #27) over 7 days from a fixed target (steel plate 35X43cm) at 30m distance .   Stability of the output was 0.3% (standard deviation), max-min spread  0.9% (900 data points excluding the 72-nd hour).  Time "0" date was 26-Aug-2008, 3PM. The sensor was configured with no temperature compensation.  Temperature range was 16-33C  as measured on the circuit board (with no enclosure). The actual air temperature was 8 degrees lower.  The target was disturbed by strong wind and had to be re-aimed at 72-nd hour.

    

FFT spectrum plot.
 Modulus of amplitude, the same target and situation as above.

Scope screen: raw signal versus time  (different situation from the above two plots).

FMCW tunning ramp plot.

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  Field testing of unit 27 - long term stability under environmental exposure.

  28-Aug-2008

Unit 27: Photograph: radar setup (75mm lens-horn) and a small perpendicular steel target plate 35X43cm, at 30m (approximately).   The setup was partially shielded from rain (under a deck) but exposed to variation of environmental factors for  7 days.  Resulting history file is shown on one of the previous pictures (History plot).

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  Linearity test.

Unit 20: linearity curve, planar target (partition wall).

Unit 20: linearity test, deviations plot, using planar target 1.8X1.8M (office partition wall).

Unit 20: linearity test results, irregular target using plastic pellets (3mm size).    The sensor was hung on a rope above a 3x3m square skip filled with plastic pellets (size about 3mm).  The surface was irregular with waves and groves ~30cm high

Unit 21: linearity test results, planar target (partition wall).

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   Temperature test.

Unit 27:  Distance versus temperature scatter plot (6.25 days) compiled from the history data log
               downloaded from the unit to a spreadsheet.  

Comments: 
 
a) The unit was tested with the temperature compensation coefficient set to zero.

b)  Data scatter is not well correlated with temperature (nor with amplitude) and has probably other contribution to variation that is stronger than the thermal drift.  That limiting factor is most likely the mechanical stability (machine screws torquing) and assembly quality of the transmitter chamber.  
              

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History

07-July 2007 - Long distance range testing.

Photo of the working prototype Rev.2.

Test using a biscuit tin as a target, placed at 90 ft (27.5m) distance. The tin size is 23x28cm and was placed with the large side perpendicular to the line of sight.

Power spectrum graph downloaded through serial/USB link, displayed using VelTerm.exe program.  Averaging accumulation length = 8 (repetitions).  Estimated (extrapolated) maximal range: 120ft (with 1" horn antena).   Estimated maximal range for the same target using 3" lens-horn antena: ~360ft (110m).  Estimated distance measurement resolution: +/- 1cm (software dependent).

Target view (click photo for higher res.)   /   Prototype radar unit view.  

3 hour stability test, history data log using target plate 13"x17" at 100ft.  10s data logging interval.  Results: standard deviation 5.24mm, average reading 31.24m.
    

  

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Contacts:

Stan Bleszynski,
R.R. 1  Lakefield,
1668 Lakehurst Rd. (Buckhorn),
K0L 2H0  Ontario Canada
+1-705-6572419
stanb (a.t) velsensor.com
stanb (a.t) ptbo.igs.net

Other products and services by Stan Bleszynski:
http://www.ptbo.igs.net/~stanb/
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