Re: Looking for Red LED gauge to measure oxygen sensor output

that I will use

pictured below is

oxygen sensor

LEDs are bright

is used to make

Why don't I

high. I'm

If you don't know much about electronics you won't save much money trying to make one.

There is something about that: you can't measure the output of an O2 or Lambda sensor with a standard DVM.

I have also heard that you can damage one trying to measure it with a DVM. I don't know if I buy this, except maybe if the loading during the warmup stage screws it up. Far fetched I think.

I do know this, you don't really get any kind of meaningful reading on a DVM from an O2 sensor.

JURB

You need a really high impedance meter, and very short or well shielded wire runs. The O2 sensor has a very high impedance output and is easily interfered with.

Funny you should say this...I've made this measurement a number of times using my Wavetec DVOM. I just wanted a permanent fixture that I could have somewhere on my dash. The panel gauge pictured in my message was being sold for that precise purpose, measuring the Lambda sensor output...I'm just trying to duplicate it without spending alot of money. Today I ran a wire from the engine compartment O2 sensor wire to the front of the car (VW Vanagon) and drove around with the DVOM hooked up to the wire and was getting readings that were consistent with open loop and closed loop status.

I looked in AllElectronics and some other sites, they have LED panel meters but so far none with .001 resolution and none that operate with 9-14 volts. I'm also not sure what kind of circuit(board) is needed to use these panel meters as a voltmeter. On the other hand buying a cheap DMM might be a solution if Il could find one that used LEDs and read millivolts. Is there such a thing?

John

used LEDs

No, they're all LCD these days and have been for years.

Maximum Input: 199.9mV DC

Supply Voltage: 5Vdc (Zener off battery should work)

Common Ground - Can monitor own voltage - very important for this application.

Your Price: $15.00 each

What I'd like to see is a DPM with a fast pointer like the Fluke '87-88 series of meters and high-impedence mV readings to 0.001 resolution. Averaging would be nice, too.

JazzMan

Hi...

I'd give my right arm for a meter that incorporated both a digital readout and a very lightly damped moving pointer...

Kinda like those wrist watches that have both hands and a digital readout at the bottom.

Take care.

Ken

On 17 Jun 2005 21:47:01 -0700, snipped-for-privacy@aol.com put finger to keyboard and composed:

No, it's true. Measuring its voltage with a standard high impedance DMM is perfectly OK, but trying to measure its resistance will inject a current into it. This current may damage the sensor.

- Franc Zabkar

My thoughts would be along the lines of using an LED VU meter originally designed to measure sound levels. With an instrument grade OP amp on the front end to provide a high impedance input. And probably some mods to make the input to the VU device DC coupled.

But you'd not do this for near $10

You could with some salvaging or utilizing free samples from semiconductor companies but not without some electronics knowledge or at least a fair amount of reading up on stuff.