I have the output of a wheatstone bridge going into an ADS1115.

I am exciting the bridge with a 24VDC supply and the ADS1115 with 3.3VDC through a Raspberry Pi.

The issue I am having is that when I look at the output from the bridge I see around 6.5mV and as soon as I connect this to the ADS there is no output.

Nothing can been seen through my software even if I turn the gain up to the maximum.

I have tried commoning the grounds of both of my supplies and still no joy.

I was wondering if anyone else had seen this issue and could shed some light on this.

• Welcome to EE.SE - when asking about circuit operation, it helps if you can provide a schematic and identify all the items as this will attract better answers. If the bridge is an off the shelf component, please identify it. – Peter Smith Mar 21 at 11:20
• What are the bridge outputs relative to ground? I bet they're much more than 3.3v when disconnected, and maybe 3.9v when connected to your ADC. – W5VO Mar 21 at 11:29
• What does "no output mean?" Zero? Or no values at all? Does your ADC work if you connect it to other signals? – JRE Mar 21 at 11:42
• The ADC does work as i have tested other signals when the brige is connected there are no values given it is outputting a "0". I do apologise for the vaugeness of my description. – Shak Jamil Mar 21 at 11:59

• @ShakJamil If each element is 700$\Omega$ it is equivalent to a 12V source with 350 ohm source resistance, so ~18mA per input (assuming Vcc stays at 5V). – Spehro Pefhany Mar 21 at 14:49