Cal Club Autocross Forums

Does an inductive timing light gun need to be hooked to the car's battery or will any 12-14v source do?

Jay W

Jayson Woodruff wrote:Does an inductive timing light gun need to be hooked to the car's battery or will any 12-14v source do?

Jay W

Any 12v dc power source should do but you may need to ground the timing light. Try it and see.

George Schilling wrote:

Jayson Woodruff wrote:Does an inductive timing light gun need to be hooked to the car's battery or will any 12-14v source do?

Jay W

Any 12v dc power source should do but you may need to ground the timing light. Try it and see.

Or...you might have to ground strap the 12V source neg to the car's chassis. The timing light could have an insulated body.

Yeah that makes sense now. I was thinking about my clamp on amp meter not needing a ground point.

And the gun has a plastic case.

Jay W

But if I had to bet money...I suspect you won't need a ground. I think the inductance loop will sense current flow as magnetic flux. There is no electrical circuit involving the car. Maybe.

Bill Martin wrote:But if I had to bet money...I suspect you won't need a ground. I think the inductance loop will sense current flow as magnetic flux. There is no electrical circuit involving the car. Maybe.

That's my position. And I'm unanimous in that.

Bill Martin wrote:But if I had to bet money...I suspect you won't need a ground. I think the inductance loop will sense current flow as magnetic flux. There is no electrical circuit involving the car. Maybe.

Yeah, the priciple of my inductive amp meter. But the timing light needs to be highly accurate, so maybe the floating ground would hurt that.

I'll test it out both ways. I found a 12v point in my engine bay just for such purposes (actually I knew it was there, but the protection cap looked like a proprietary connector until I figured I could unsnap it).

Jay W

Jayson Woodruff wrote:

Bill Martin wrote:But if I had to bet money...I suspect you won't need a ground. I think the inductance loop will sense current flow as magnetic flux. There is no electrical circuit involving the car. Maybe.

Yeah, the priciple of my inductive amp meter. But the timing light needs to be highly accurate, so maybe the floating ground would hurt that.

I'll test it out both ways. I found a 12v point in my engine bay just for such purposes (actually I knew it was there, but the protection cap looked like a proprietary connector until I figured I could unsnap it).

Jay W

Spare 12V battery would solve this right?

It will work with external power. Well, mine does.

Jayson Woodruff wrote:

Bill Martin wrote:I found a 12v point in my engine bay just for such purposes (actually I knew it was there, but the protection cap looked like a proprietary connector until I figured I could unsnap it).

Jay W

If were talking the Prius... that little red flip cap in the fuse box is also where you jump start the car.... don't go messing with your battery 12 volt battery directly, unless you want to mess with the three phase electronics in your car.

You will find a large metal post near the head that sticks up, that's the official jump start ground point too, within easy reach of most jumper cable split ends without having to tear them farther apart.

All in the manual.... but who reads those?

Miata.

I doubt you can set the timing in the prius. I have "jumped" it with one of our little timing light batteries though.

Jay W

Craig Naylor wrote:

Jayson Woodruff wrote:

Bill Martin wrote:I found a 12v point in my engine bay just for such purposes (actually I knew it was there, but the protection cap looked like a proprietary connector until I figured I could unsnap it).

Jay W

If were talking the Prius... that little red flip cap in the fuse box is also where you jump start the car.... don't go messing with your battery 12 volt battery directly, unless you want to mess with the three phase electronics in your car.

You will find a large metal post near the head that sticks up, that's the official jump start ground point too, within easy reach of most jumper cable split ends without having to tear them farther apart.

All in the manual.... but who reads those?