Starter solenoid current?

All you do is use a shunt if that is what you are worried about. But the easiest way is to use a clamp meter.

That's a rather optimistic view of the effectiveness of the fuse. The fuse is intended for personnel protection - they rarely protect the meter from *high* currents - errant students demonstrate the art of meter destruction to me at regular intervals.

They often blow the tracks away before the fuse blows, sometimes even the internal shunt goes before the fuse does.

I've got one. Actually, a couple.

Please stop trying to lend me stuff. Everything that I've ever borrowed uses up space in my shed. ;-)

I also have a hand-held, digital 'scope. One of the clamp meters has peak-hold -- I'd forgotten about that. It might do the trick.

Well, it'd tell me the current through the circuit. Which isn't necessarily the same current that'll be drawn when the long wire is replaced with a short one and a transistor switch.

That's a rather optimistic view of the effectiveness of the fuse. The fuse is intended for personnel protection - they rarely protect the meter from *high* currents - errant students demonstrate the art of meter destruction to me at regular intervals.

They often blow the tracks away before the fuse blows, sometimes even the internal shunt goes before the fuse does.

Cheers, Paul Saccani Perth, Western Australia.

Face it, when you pay $5 for a DVOM today (WalMart, Harbor Freight, etc.) any fuse is a luxury.

Careful someone may take you up on that!

Many (better) clamp-on meters have a peak read feature that will save the highest reading as well display the current value. Very useful for seeing start-up surges.

Again, some DVOMs have RS-232 or other computer output that may allow similar features.

Ah, but we're over testing, I think, the OP's problem!

Walmart? Harbor Freight?

Surely you mean Bunnings or Repco :)

he he!

...and now we get to what you are really up to. No doubt with a MOSFET in mind. Don't neglect the back EMF, and the transient inrush current could be significant.

You could always buy a COTS solid state relay - for you to engineer as good a solution from parts for the hostile environment it can expect to live in, is something that will cost you a good deal more than the $23 for a COTS 80 A 0-100VDC solid state relay.

Uh, sure...

Shouldn't you be waiting for some sucker to post in alt.marketing.online.ebay? I wonder how Lumpy is going...

That's my main concern. The inrush and other transients.

BTS50055-1TMB is designed for the environment, provides useful feedback and therefore diagnostics (at about $6). I need to determine the solenoid current to allow for an adequate "overkill".

In retrospect (?), I can prototype just the power circuit to make sure that it doesn't release the magic smoke. Although testing would only be for the conditions under which I'm testing ... so need to make them as bad as possible.

A lot of DMM don't come with HRC fuses. I always replace those with HRC before letting the unwashed use them. Nonetheless, it still happens with depressing regularity. I also use a cheap $1.50 6A fuse instead of the $60 13A fluke DMM fuse. The cheap will never blow later than the expensive one for an overload, but of course, is not rated for 13A continuous. As none of the training program requires more than 6A continuous, it is OK.

I did a test program before doing that, and it was quite interesting. At 4.5 A constant, the Fluke blows after a while, even though it is rated at 13A constant, whilst the 6A is happy, and always blows sooner than the fluke fuse with a genuine overload.

Besides us not being merkins, the fuse is there to protect you more than the meter.

Bernd never borrows from me...

Not actually that good for inrush currents.

That will not do the job. The measurements are not take frequently enough.

It isn't really designed for the environment, nor is it directly suitable for inductive switching. Honestly, go the SS relay - it is made for the job, has suitable contacts and is a dead easy integrated solution.

Unless. you have a bucket of the BTS you need to get rid of, of course.

A lot of DMM don't come with HRC fuses. I always replace those with HRC before letting the unwashed use them. Nonetheless, it still happens with depressing regularity. I also use a cheap $1.50 6A fuse instead of the $60 13A fluke DMM fuse. The cheap will never blow later than the expensive one for an overload, but of course, is not rated for 13A continuous. As none of the training program requires more than 6A continuous, it is OK.

I did a test program before doing that, and it was quite interesting. At 4.5 A constant, the Fluke blows after a while, even though it is rated at 13A constant, whilst the 6A is happy, and always blows sooner than the fluke fuse with a genuine overload.

Cheers, Paul Saccani Perth, Western Australia. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Have you tried RS Components for HRC Fuses. My fluke takes them and they are $28 for a pack of 5 last time I bought one. The downside for me is that they only sell them in packs of five, for you that is a bonus ;o)

I see a bunch of posts there, so I suspect he's going balls to the wall!

As for cheap DVOMs, I was in Harbor Freight the other day. The deal was spend a relatively nominal amount, and they gave you a free DVOM. So I got two!

I tested their accuracy, it was OK (not great, but usable) so for the price a winner.

I know the ones you mean.

A fluke fuse is a HRC fuse, but it is a very special one. You won't get an equivalent from RS for less than $50 each. You will get ones that are HRC and the same size, but they are not equivalents.

Inside a fluke fuse, you have the usual sand, but the fuse itself is a perforated strip, folded concertina style on the perforations. That's what lets it react so quickly to overload to protect not just you, but the meter too (though fluke meters usually have VDRs as well).

The ones that you are getting, if rated to 1000 V and 5kA will provide personnel protection, but will diminish the meter protection significantly.