Injector measurement
I was interested in injector opening/closing time regarding to flyback setups.
All of the below measurements made on a 12 Ohm Hi-Z injector dry -without fuel pressure-, and PowerFlyback installed inside the ECU. No PWM-ing was enabled, pulse width is ~14ms.
Voltage was 12.1-12.2V, voltage/current measurements were made after a 0.3Ohms resistance, so test setup is like:
+12.2V____[0.3Ohms]____*Measurement*____[injector]____INJ-OUT
The results:
Red channel means measurement voltage (or current).
Blue channel means mechanical movement/noise.
- 1. graph is one open-hold-close pulse with no external flyback. Closing time is 1.7ms
- 2. graph is similar open-hold-close pulse with 18V Zener flyback. Closing time is ~0.95ms
- 3. graph is similar open-hold-close pulse with 30V transient diode flyback. Closing time is 0.9ms
It's visible on the red channel that after opening (about 1ms later) current has a pulsation which shows the movement of injector iron core. At the same time mechanical noise started (blue channel).
At closing phase there's not visible current-pulse in red channel but a spike goes well over starting (+12V) voltage which is the inductive "kick-back" or flyback current. Blue channel's mechanical noise shows here the exact position of mechanical injector closing.
As my movement/noise detection (knock sensor) was nearly installed on the injector it's coil slightly picked up injector current, so on the blue channel it's also visible when injector current switched on/off (a single spike before noise).
