Ultrasound - AD600 ground problems???

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
    I知 a Brazilian researcher designing an ultrasound range finder fo
Biomedical Department. This is a picture from Orcad project schematic:
http://vesatur.sites.uol.com.br/temp/schematic.jpg
I placed an AC generator (Vin) to simulate the ultrasound reflected wav
with 1mV amplitude and 700kHz.
This is the simulation:
http://vesatur.sites.uol.com.br/temp/simulation.jpg
Gain = 41dB.

    I知 designing an ultrasound receiver with AD600 (Analog Devices) t
amplify the reflected wave with a preamp supplied by an OPA350. I知 reall
confused with all those AD600 ground connections and I知 aware if I make
mistake it will produce a lot of noise and it will interfere in m
measures. The AD600 IC provides separated ground references for inpu
(A1LO/A2LO) and output (A1CM/A2CM). Datasheet warns: 的t is important tha
A1LO and A2LO be connected directly to the input ground. Significan
impedance in these connections reduces the gain accuracy. A1CM and A2C
should be connected to the load ground.
    I知 using the same single transducer element for transmission an
reception then transducer has to be connected with transmitter an
receiver circuits. In my schematic, I labeled ground plane with number 1
These are my ground considerations:
    Label 1 - I attached all transmitter components and DC regulator
connected to VPOS (pin 13) and VNEG (pin 12) in AD600 to ground plane.
    Label 2 - I presumed that I should connect the input grounds (A1LO pi
3 /A2LO pin 6) and gate input (GAT1 pin 4/ GAT2 pin 5). At the sam
reference, I connected the voltage limiter made by 1n4937 diodes and th
preamp ground connection.
    Label 3 - I connected the output ground pins (A1CM pin 15 / A2CM pi
10) with the load resistor as an output ground reference.

    Where should I connect the transducer? There are 2 options: the groun
plane with the transmitter components or with the AD600 input groun
reference.
Should I isolate AD600 ground reference from next stage (buffer + pea
detector)? Is it safe connecting peak detector and AD ground output t
ground plane?

    I知 so sorry for my poor English.
        Thanks in advance,

 Claudio Klein



        
-> This message was sent using the  web interface o
www.EmbeddedRelated.com <-

Re: Ultrasound - AD600 ground problems???
Quoted text here. Click to load it
... snip ...
Quoted text here. Click to load it

You are making things over-complicated.  You simply want to make
sure that no noise induced currents (which includes digital
circuits) appear in impedences in the signal circuit or in any
voltage reference circuits.  So be aware of the currents, and make
your connections accordingly.  Also beware capacitive coupling.

--
"If you want to post a followup via groups.google.com, don't use
 the broken "Reply" link at the bottom of the article.  Click on
We've slightly trimmed the long signature. Click to see the full one.

Site Timeline