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Old 11-02-2016, 12:25   #16
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Re: Looking for DC current transformer rather than Shunt

We were discussing DC clamp meters in this thread: Solar Multimeter Testing

It turns out the Fluke unit I have is the "337". They don't make that anymore, which is why I didn't find the link.

The Sears meter I mention only costs about $45, and it seems to work well. Other inexpensive DC meters are also noted in the thread.
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Old 11-02-2016, 13:19   #17
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Re: Looking for DC current transformer rather than Shunt

I've bought a few DC clamp ammeters off Amazon with good results (under $60.00). I will look if I have part #'s. They were pretty close to the accuracy of our fluke in the shop as well.
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Old 13-02-2016, 09:20   #18
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Re: Looking for DC current transformer rather than Shunt

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Originally Posted by Frankly View Post
For your proposed set up don't see a compelling reason to know the AH or A draw from the bow battery. Your main interest is just keeping an eye on the fwd battery to make sure that it is getting recharged. The second voltage input on the Link 20 should take care of this. Just tap the front battery using the BS fuse block.

A DC clamp on ammeter to check on the two DC motors from time to time might be a nice preventative maintenance item. No DC transformers but magnetic sensors will give you the current in the wire.

Dig around in the Blue Sea technical info. They did some actual testing on ANL fuses. Turns out that they are really slow blow and maybe should be downsized depending on the application.
Franky

I'm begging to lean towards no ammeter installed, but just use a clamp on meter (which I have) to check every so often.

I will probably end up using an ANL fuse from Vetus which is designed for the thruster as it's curve is quite different than Blue Sea
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Old 13-02-2016, 10:05   #19
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Re: Looking for DC current transformer rather than Shunt

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Why would you not want to use a shunt? if the shunt is rated for 500 amps that should be fine. all your ammeter does (in reality) is measure volts. a 500amp 50mv shunt just reads 50mv by the meter (at 500amps of current passing through the shunt) . your windlass battery wont even notice the shunt.
The rating of the shunt tells you what the voltage drop will be, in the above case 50mv at 500amps of current draw. Shunts are pretty robust, trouble free devices and fairly low cost.

On the anchor winch application I'm not sure that knowing the current draw is going to be very helpful anyway as it depends on the load which varies considerably when pulling an anchor. Similar to a degree on the thruster.
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Old 13-02-2016, 10:14   #20
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Re: Looking for DC current transformer rather than Shunt

I note that my clamp on DC ampmeter has a a'zero' button, because the current measuring sensor tends to drift or there are outside fields. It probably would't work as well as a shunt in a permanent installation.
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Old 14-02-2016, 11:47   #21
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Re: Looking for DC current transformer rather than Shunt

Check eBay , reasonable DC current clamp meters starts under $50, Fluke 362
under $150.
But for continues monitoring of DC current, you need
Split Core DC Transformer conected to panel meter.
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Old 14-02-2016, 13:17   #22
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Re: Looking for DC current transformer rather than Shunt

If you want to roll your own DC current sensor (full-scale ranges from 50 to 200A) you can use one of these integrated circuits: Allegro MicroSystems - 50 to 200 A Integrated Current Sensor ICs
Or you can use a resistive shunt. One advantage of the sensor IC is that it has excellent isolation and can be placed in either the high side or the low side. One advantage of the resistor shunt is that it's simple and works well.
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