@dron_gus says just a resistor divider and we are in business? What about heater control - is there any strategy or just constant power?
Huh? They require current sensing on a constant voltage source. Supply 0.4v, measure current source/sink.
Re: Medium-band oxygen sensor
Posted: Fri Nov 25, 2022 8:35 pm
by AndreyB
Forgot to attach the schematics
Re: Medium-band planar oxygen sensor
Posted: Fri Nov 25, 2022 8:40 pm
by mck1117
It needs the voltage to be stable, and yet have enough sensitivity to actually measure useful information. The sensor's linearity is only assured when the voltage is stable. 0.36 to 0.50 volts probably doesn't count as stable. You could probably use the sensor if we had the characterization information about its behavior, but that's only really available for stable voltage, not variable voltage.
That's also a 0.14v range, most ECU divide that so it's actually 0.096v at the ADC, which is only 119 ADC counts. Not a lot of significant figures, but maybe enough.
yes, I did a design a while ago that uses a jellybean dual opamp and some passives. Never fabbed it, though. Will share it if I still have it when back from my trip.
Re: Medium-band planar oxygen sensor
Posted: Sat Nov 26, 2022 7:58 pm
by AndreyB
Cold sensor, heater resistance 3Ohm. Lab power supply reports 3A starting consumption which falls to 2A in 20 seconds. Three minutes later current falls to around 1.7A and stays at 1.7A for next hour. Heater resistance when hot 6A-ish.
Looks like this heater just needs constant power and it does the rest itself.
Re: Medium-band planar oxygen sensor
Posted: Fri Dec 02, 2022 7:50 pm
by AndreyB
Between two DMMs in 20mA mode I am failing to see any life from the sensing part of the sensor. Have I fried my sensor or do I have to heat it to get current flowing?
white wire: signal negative
blue wire: signal positive
WhatsApp Image 2022-11-27 at 11.31.03.jpg (342.94 KiB) Viewed 14685 times
Re: Medium-band planar oxygen sensor
Posted: Fri Dec 02, 2022 7:51 pm
by mck1117
it needs to be hot to work - extremely high impedance when cold