O2 Sensor Voltage

[Peter D. Hipson]

most of these digital meters must have an isolated power supply, that is
the common power supply lead cannot be connected to the common measured
voltage. 

At 05:00 AM 9/8/1999 -0400, you wrote:
------------------------------
>
>Date: Tue, 07 Sep 1999 22:12:46 -0500
>From: Tom Sharpe <twsharpe at mtco.com>
>Subject: O2 Sensor Voltage
>
>Group, I made a 10 LED O2 display which worked fairly well but was hard
>to read as I used assorted LEDs, etc. and it flashed a lot.  I built
>another using an LCD display from a cheap meter (0-200 mv), a 9v power
>supply (7809 chip etc.) and a 1/10 voltage divider (set of 1/4w
>resistors). It works from a 12V power supply and a 1.5V battery -- reads
>.1593 volts
>
>It has 4 wires - sensor in, sensor ground, +12 and ground. I wired it to
>my efi harness - replaced the LED display. I used a common ground (same
>as the LED one). The meter displays 1 indicating the voltage is greater
>than scale (> 2 volts).  My volt meter shows +14v (ok here) and .4-.7 v
>on the O2 sensor (engine running).
>
>What's wrong? I thought O2 sensors read 0-1V.  Is the meter too
>sensitive? Am I getting feedback somewhere?  Do I need another ground?
>HELP!!!   TIA.  Tom
>
>------------------------------

Thanks, 
        Peter Hipson (founder, NEHOG)
        1995 White NA Hummer Wagon