Contents

Modifications

The following modifications were made to the standard 6500 Ranging Board to enable it to drive the new Series 9000 Environmental Grade Transducer. 

• The 420 kHz ceramic resonator is changed to a 385 KHz resonator.  This changes the final drive frequency from 50 kHz to 45 kHz. 
• The L1-C1 filter circuit should be retuned for 45 kHz.  To do this:
• Replace capacitor C1 with a 0.012 uF capacitor or add a 0.0022 uF capacitor in parallel with the existing .01 uF capacitor C1. 
• Fine tune L1 to obtain the maximum amplitude voltage signal of the returning echo as observed on the Analog Chip (SN28784), Pin 9. 
• Add the impedance matching RC circuit consisting of a 470 ohm resistor and a 1000 pF capacitor.  These will need to be rated to handle the 400 Volt difference created when the board drives the transducer. 
• Replace R1 with a 25K ohm potentiometer, VR2, to provide finer adjustment of overall circuit gain.he specified values, the window is roughly 2.30V to 2.70V. 

Schematic with modifications.

Impedance Adjustment

One option to adding the RC impedance matching circuit is to instead switch the XDCR wire (E1) to connect directly to the center tap of the transformer on the 6500 board .  The transformer has two pins on one side and three on the other side.  The center tap is the middle pin side with three pins.  This pin is currently not used on the board.  This roughly adjusts for the impedance mismatch of the Series 9000 Transducer instead of using the RC circuit shown above. 

Circuit Gain Adjustment

You may not need to switch R1 to a variable resistor.  This has not been necessary on some of the boards we have modified.  You may want to try the other modifications first and test the board before making this change. 

Related Links:

Senscomp (Polaroid) Sonar Ranging Primer