[SI-LIST] Re: Electrical wiring questions
- From: steve weir <weirsi@xxxxxxxxxx>
- To: powersurf@xxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Fri, 17 Feb 2006 16:06:22 -0800
Mike, you need to do a noise sensitivity analysis.
If you are relying upon a common rail to make ratiometric
measurements, then you will impair the results by some amount with
your proposed arrangement. If your measurements are not ratiometric,
then you need to insure sufficient absolute accuracy end to end to
meet your requirements. The various analog players, LTC, Maxim, NS,
TI, ADI etc all have substantial appnotes.
Steve.
At 03:43 PM 2/17/2006, Mike S. wrote:
>Hello to all,
>I would like to ask for some advice and orientation on electrical
>wiring matters!
>I believe this configuration is very common:
>I have an analog sensor with 3 wire leads (Vcc -5 V-, GND, signal)
>that will be sampled by a fully differential ADC that is on a separate
>PCB. I only have one 5 V power supply to power both the sensor and the
>ADC PCB (this card is also 5V). I believe that the best way to connect
>this setup is to power the ADC PCB and then, with a single connector
>from the ADC PCB to sensor, containing 3 pins (Vcc,GND and signal).
>This way would avoid ground loops. The problem is that I don't have
>such a connector in the ADC PCB. In fact, I only have a connector with
>2 pins (Signal+ and Signal-, that are the ADC differential pins). So
>the sensor must be powered from the same power supply, but with a
>different cable that will not originate in the ADC PCB, but directly
>in the power supply.
>Since the connector to the sensor in the ADC PCB doesn't have any
>ground pin the sensor return current would have to return in the power
>supply ground wire. Although the ADC has fully differential inputs
>(that would cancel any induced currents in the loop) I don't think
>this is a good solution. Is it?
>
>Any suggestions or comments are welcome.
>References like books or other publications that deal with these
>matters are also welcome.
>
>Thanks in advance
>Best Regards
>
>B. Mike
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