Test your skills boys

[tmann45]

Big story there, I've had a FLUKE 88A for 25+ years and make my living with it.. if your checking Amps in millivolts,,, somethings WRONG !! most DVM's are fused at 10 Amps... Carry On............

With an external shunt you are checking the voltage drop across a known resistance, thus telling you amps using ohm's law, simple way to measure greater than 10 amps that your Fluke (and most other DMM's) is limited to.

But if you have a clamp on forget about it.

[zenoahphobic]

How accurate would a clamp meter be?
I've never used one because they seemed to be used in high voltage dangerous stuff.
And I guess that they are more of a troubleshooting test equipment that is also expensive hard to justify as a "home" tool.
With outboard or engine stuff, I guess the large current items are starter motor, alternator and lesser current users such as trim, fans etc.
The first two generally are not fused as I suspect absolute measurement values tend to not be very usefull.

If one was to teach mechanic students about the use of DMM in the marine environment , the most important thing is to use sharp tipped probes and ensure absolute good contact, as invariably everything is well coated/sealed to avoid corrosion.
The second is the understanding that everything has electrical resistance so readings vary along points in a circuit. And that means understanding what is significant and what is not e.g. Voltage drop. (Boscoe might tell you like vacuum there is no such thing. There is only more or less voltage)

[rodbolt17]

sorry Zeno
your wrong.
FIRST thing I teach is NEVER EVER breach the wire insulation.
just don't do it.
but this stuff is actually easy if you sit back and observe.

[rodbolt17]

maybe boscoe can simply post the 4 articles and yall figure out which are simply WRONG.
march 2016 onboard.
wrong information.

[zenoahphobic]

sorry Zeno
your wrong.
FIRST thing I teach is NEVER EVER breach the wire insulation.
just don't do it.
but this stuff is actually easy if you sit back and observe.

You're absolutely right (I didn't say to breach the insulation).
At some point, termination or connector, one has to have a "clean" contact. To minimise damage (there has to be some disruption), a sharp small point is the only way to achieve a good electrical connection for voltage and small current measurement.
Sitting by and observe is fine if we can be there in person. Internet that's hard but getting better with quality pictures and video.
Yes might be arguable what is the first thing to teach.
The reason for wire puncturing, is confined space , or length of wire. There are physical limitations in the length of meter probe leads, and most importantly the length of our arms and the length of our necks to see the meter. Good tuition required to get around these physical difficulties.

[rodbolt17]

NEVER EVER pierce the wire insulation, JUST DONT DO IT.
make jumper extensions.
make connector adapters.
use paper clips slid up the wire at the connector.
just NEVER pierce the insulation.
it wont seal and possibly will nick a wire.

I have a few jumper leads about 12ft long.

[rodbolt17]

so no one wants to figure out and post the WRONG stuff on the march 2016 onboard?
its ok, no one at the shop has figured it out yet either.

[99yam40]

Post a link for people to see it.
I have no idea where to find it

[MNY4m4h4]

I'm just an electrician who comes here to learn from the guys here who know more about my motor than I do and have been kind enough to help me in the past.

Let me say I don't know what kind of meters you use and I would just use a clamp on to measure current. As to the shunt issue, I'm sure it would work but it wasn't explained well and voltage is not "Consumed", it drops as a result of the resistance in the wire and by knowing the resistance value and the drop in the voltage one can calculate the current. The dropped or "Consumed" voltage is actually converted to heat.

That said I can offer these comments that may help clarify electricity and how it works.

Voltage is always constant in parallel and amperage is constant in series. So when you measure voltage you do it in parallel. This is why we wire in parallel, if we didn't all of our devices would not work as they wouldn't have the proper voltage to operate, which can damage components if you deviate too much either way.

Meters have a setting for measuring volts or amps and if you are set to measure volts and complete the circuit with your meter you will let the smoke out and damage your meter. Always make sure you check the setting on your meter.

Amperage is constant in series, so when we measure amps we do it in series. As such you need to make sure you set your meter to read amps and then use your meter to complete the circuit to read the current. As electricians we use clamp on meters for safety, at 12V it is not as dangerous, but electricty should always be respected. Honestly we only did this in labs in school many many years ago with old fused analog meters, in the field you ALWAYS use a clamp on, as you can only read current when the load is energized.

Resistance in ohms law is simply load, which can be a motor, heater, light, whatever. Often measured in watts or horsepower. So if you know any two of the three, Volts, Amps, or Load you can calculate the third.

For instance if you have a light bulb that is 12W and its hooked up to 12V, the current should be 1 Amp. Unless you have transformers in your systems, the voltage should always be 12V. Voltage drop could be a concern but if you use a big enough wire it shouldn't be and if its factory wiring I would't think its an issue.

Amperage is a result of a given voltage across a load. Amperage is never a constant you bring to the situation (We don't wire things in series). In short you should know the voltage and you know the load, so you should know what the amps should be from a simple calculation. If you read the amps and it is not what you expect to see then you have a problem. Either not the right voltage or something is wrong with your load.

Amps X Volts = Watts (Load)

Amps = Watts(Load)/Volts

If this helped great, if it made it more confusing then you know how I feel when I come here looking for answers,

[zenoahphobic]

Post a link for people to see it.
I have no idea where to find it

Here here.

Or is that where where?

[zenoahphobic]

MNY,

I like the description of load as resistance although you also call it power (different equation V/I as opposed to VxI).

That doesn't matter as it does reduce confusion as people sometimes think if you increase resistance you increase the load; the opposite, of course is true.

Different professions use different terminology.

[rodbolt17]

rather than read erroneous info on the net.

google kirchoffs law of voltage and kirchoffs law of current.

yes you can wire series and parallel as well as series parallel circuits.

[zenoahphobic]

rather than read erroneous info on the net.

google kirchoffs law of voltage and kirchoffs law of current.

yes you can wire series and parallel as well as series parallel circuits.

I think MNY was referring to the type of wiring he is exposed to. I don't know if he has anything to do with house wiring, that example holds true to what he is saying- nothing is wired in series except the fuse/switch (might look like GPO's are but they are not).

Now this Kirchoff fellow.

[rodbolt17]

Kirchoff knew his trons.

[zenoahphobic]

Kirchoff knew his trons.

Yes, when working with electronics, very important to know his two laws.