Make a test circuit (cheap 2 resistors used instead of the LSU4 sensor) for initial WBO2 pump_pw_zero and nernstdc_target (or even pump PID) calibration:
Pump- (100Ohm) Nernst (100 Ohm) Pump+
- Rm=100 Ohm between nernst and pump-
- Rp=100 Ohm between nernst and pump+
- measure the resulting voltage (with DVM, DC voltage mode), with the pump- signal as base. Connect the DVM black wire to pump-
Typical voltages with wbo2 OFF (engine not running, trigger signal not played)
- pump- : 0V (what we measure against)
- GND : -4.1V (since we measure against pump- that is +4.1V above GND)
- Adjust wbo2_pump_pw_zero until OK. Higher value results in higher voltage, typical calibrated value: 0x65+-03 (that is 101+-3). Restart before measurement, but after the changed wbo2_pump_pw_zero is saved
- nernst: +-2mV (/100 Ohm)
- pump+ : +-4mV (/200 Ohm)
Typical voltages with wbo2 ON (engine running or trigger signal played or wbo2 forced on with mde02 command)
- pump- : 0V (what we measure against)
- wbo2_pump_pw_zero can be calibrated this way, usually 0x65+-03 (that is 101+-3). Restart before measurement, but after the changed wbo2_pump_pw_zero is saved
- nernst: +450mV +-30mV Adjust wbo2_nernstdc_target until OK. Higher value results in higher voltage. Typically 0x86 +-5 (that is 134+-5)
- pump+ : appr +900mV (is required here so the nernst voltage will be 450mV above pump- .... but the exact voltage here is not very interesting as nernst is used for feedback)
- note: 12V or higher supply voltage needed for this test. The pump will not maintain target nernst voltage with this test-setup if VBATT<12V
Misc notes
- wbo2_pump_pid_kd=00 (I doubt that any other value makes sense)
- wbo2_pump_pid_kp=20..40 ... too high value will result in significant oscillation.
- Make sure the multiple of config values: wbo2_pump_pid_ki * wbo2_pump_pid_ilimit is high enough. If this is too low, pump+ will be limited: as a result, nernst_dc_target can not always be reached.
- I revised a theoretical reasonable maximum for the multiple : wbo2_pump_pid_ki * wbo2_pump_pid_ilimit (sg. like 0x80 * 0x0A) but in practice 0x80 * 0x40 was used to reach target.
- the PID integral term will rail faster for lower pump_pid_ilimit
Don't connect real sensor until PID (and nernst_dc_target) is tuned with that so nernst is stable and fine (450mV above pump- ).
[[Detailed.Sensor.Wide.Install]]
See also: