lambda sensor simulator

hi,
i have a other circuit with a 32bit processor that is managing one wood boiler. The other PCB is working with a Lambda sensor.
but if i want to simulate the boiler is a bit difficult to light out some fire and make the test. also it is difficult to create constant air mixture to make a simulation.
this is the point that i am thinking to use arduino. i can produce a constant signal to simulate the sensors signal.
and here is the problem. arduino has a 1024 steps on analogue output. so, every step is 4.883mV but the arduino is working in an area form 0-40mV. that mince that i have less than 40/4.88=8.19==8 steps.
and this is my question. how i can make the 0-40mV with 100 steps? external D/A?

Bosch.pdf (207 KB)

The Arduino has not analog output.
It does have a digital PWM signal to dim motors and leds.

Only the Arduino Due has analog outputs

You can use a regulator Arduino board, with some external components. That can be a DAC, but perhaps also a programmable resistor.

and here is the problem. arduino has a 1024 steps on analogue output. so, every step is 4.883mV but the arduino is working in an area form 0-40mV. that mince that i have less than 40/4.88=8.19==8 steps.
and this is my question. how i can make the 0-40mV with 100 steps? external D/A?

It's confusing, if you mean analog output, than analogWrite supports only 256 steps. You can get any voltage in a range you need simply smoothing out PWM by resistor + cap circuits, than two resistor voltage divider could bring it down to 40 mV. And 256 steps become compressed in 0 - 40 mV

From what I read about these sensors, they just produce a voltage.... If that's correct (and I'm not missing something, which is quite likely because it's 6am here), can't you just produce a varying voltage using a potentiometer with the sensor's input voltage across the ends and the varying output on the wiper?