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Hi,

I need to straighten a few things out.

I have a sensor that has four connections.

GND 5+ Volts (Power source) 0 Volts 1 Signal out a variable voltage, I read this signal for my output.

Normal I would imagine that I would connect my 0 volts to the neutral supply.

But I am trying to use the above device on a portable device.

I imagine I would connect the 0 volts up to the neutral. But how do I supply a ground? I'm guessing the ground is possibly connect to the electrical shielding on the cable but I'm not sure.

All the best Duncan.

"Normal I would imagine that I would connect my 0 volts to the neutral supply."

That sounds dangerous ...

Can you post a link to a datasheet for this sensor?

By neutral I mean negative.

I have connected the GND up to a physically grounded source.

My 0 Volts to the negative. And the 5+ volts to a volt supply.

Now via my signal out I am receiving a voltage that swings between the specified range of the spread sheet.

Here is a link to the sensor. www.plesseysemiconductors.com/doc/?id=291346

If you think I should be doing this another way I would love to know how I could improve this.

If I made this portable what would you suggest as an alternative ground?

You should just be able to connect Pin2 Earth (Green) to Pin4 0V (Blue).

There's no magic: the earth is just the screening can which connects to your system ground. If Pin3 +6V (Red) is connected to a positive supply of say +3V and Pin4 0V (Blue) is connected to a negative supply of say -3V, then Pin2 Earth (Green) would go to the mid point of these two supplies = 0V.

The datasheet and apps notes are very poorly written and do not make any of this clear.

Thanks for clearing this up.

I understand that the screening is designed to remove electrical interference. Will connecting the earth to the negative supply remove this? Or will it somehow create some other interference?

Thanks again.

Aaaaaah.

Simple question. Very complex answer.

The simple answer is yes.

A more complex answer is yes but only if the rest of your application is designed to minimise susceptibility to interference (noise, hum, spikes, pick up, blah, blah, blah).

You can think of the sensor as being a microphone in a PA system. They are in metal cases that are connected to the outer screen of the microphone cable.

This screen is connected to the signal ground of the mixer/amplifier input. The signal ground of the mixer/amplifier is usually connected to the mains earth where the supply comes into the case.

The signal is carried on the inner (screened) wire to the mixer/amplifier input.

These may help:

http://www.ofcom.org.uk/static/archive/ra/topics/research/RAwebPages/Radiocomms/index.htm

http://www.ce-mag.com/99ARG/Bjorklof137.html

http://www9.dw-world.de/rtc/infotheque/interfer_screen/interferscreen.html

Especially: have a look at the references on the last page of:

http://www.analog.com/static/imported-files/tech_articles/MS-2066.pdf