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Summary of change:
Make a '''test circuit''' (cheap 2 resistors used instead of the LSU4 sensor) for initial WBO2 PID tuning: * Rppn=100 Ohm between pump+ and nernst * Rnpm=100 Ohm between nernst and pump- That's all. This way the current "pump" (current generator) is tested, which is an important part of the WBO2 circuit. You can measure the resulting nernst voltage (with DVM, DC voltage mode): Over Rnpm, Urnpm=appr. 450 mV (400..490mV) should be measured. ----- '''Setup''' * Urnpm, Rnpm does not mean much, except to the firmware folks.. * Lets look at what stuff means.. * This setup is on an unmodified 3.2 board using the new 12x12 firmware code as released.. no changes yet. * The board is being triggered and running @1200RPM Signal hookup... *Pump- (100Ohm) Nernst (100Ohm) Pump+ Resultant Voltages... * Pump- --> Pump+ '''0.415V''' * Nernst --> Pump- '''0.210V''' * Nernst --> Pump+ '''0.205V''' * Gnd --> Nernst '''4.18V''' * Gnd --> Pump- '''3.97V''' * Gnd --> Pump+ '''4.38V''' Questions: *Now which of these measurements is important? *How do I adjust the values to make it right? *What should the default values be for a LSU4 setup? In fact you can disturb the circuit by changing the resistors to some degree, or connect a resistor (like 1..10k) between nernst and GND (or between nernst and 5V). The (faked) lambda reading will change, but the Urnpm=appr. 450 mV should hold. '''Reading is slightly off, say pump- is 3.98V (relative to GND) and Unernst=4.3V (relative to GND) instead of 4.43V. How can it be tuned?''' * 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. * '''nernst_dc_target ''' adjusts above mentioned Urnpm (target-value). If other factors are OK, the target nernst DC voltage (ideally Upump- + 450mV) can be directly set with this. Adjust until OK. * Make sure the multiple '''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 that might be off a few bits (dunno where I got it wrong): ** in practice this multiple was not enough to raise pump command sufficiently (from 0x63 to FF) so I had to use higher, appr. '''0x80 * 0x40''' values. ** While the multiple value is the most important, for same multiple value, the PID integral term operation will be faster for lower pump_pid_ilimit (and necessarily higher wbo2_pump_pid_ki, so the multiple remains same) Don't connect real sensor until PID (and nernst_dc_target) is tuned with that so nernst is stable and fine (450mV above pump- ). [http://megasquirtavr.sourceforge.net/manual/Detailed.Sensor.Wide.html#Install [Detailed.Sensor.Wide.Install]] ---- '''Go back to:''' GenBoard/Manual/WBSensor GenBoard/Manual
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