Injector driver question...

[rr]

Doesn't make sense, I'd have a look at everything that could
effect the current reading. Your test equip, P/S voltage, inj
resistance. Somethings not right. Try just 12.0v and a DVM in
current mode across the sat inj, see what that gives.

You'll probably find something goofy someplace.

BobR.

Hugo Villeneuve wrote:
> 
> Hi all,
> 
>     I have designed and tested an injector driver based on the LM1949. I
> want to be able to run low impedance as well as high impedance type
> injectors. I tested it with low resistance (2.4 ohms) injector and the
> operation was as expected (at least on the scope screen!) with a peak
> current of 4 A and hold at 1.0 A. The rise time is 0.8 mS.
> 
> When I tested it with a high impedance injector (14.9 ohms), the peek
> current was about 2.5 A and it took 4mS (seems very long to me...) to
> rise to this value. After that 4 mS period, the timer fonction of the
> LM1949 lowered the current to the hold mode of 1 A, as expected.
> 
> My question is : why the current is so high with the high impedance
> injector ? If we divide the battery voltage by the impedance of the
> injector, we get 12 / 14.9 = 0.8 A, which is the value of the current in
> the steady state.
> 
>     Hugo Villeneuve.