Best Affordable Device To Measure How Much Current A 36v Motor Is Using?

[rs14smith]

Actually it is pretty simple.

The shunt is no more that a very high power low resistance resistor. When current runs through the low resistance there is a small subsequent voltage drop. That voltage drop is proportional to the current passing through to the load. The tie points on the block for the meter are precision points across the resistance. I can post a few images of shunts I have laying around if it would help but what you see is what you get.

Ron

Yeah I figured it worked similar to that, just did not appear that way. So would I have to worry about my nonstandard 36v if I just go with an analog meter?

Like if I found a 50A > analog meter (includes shunt), would it be as simple as hooking it up in series with my motor, and I'm done? Or will I still probably have to use a regulator of some sort?

 

[KeepItSimpleStupid]

The SHUNT is a very low value resistor with 4 Terminals. Why 4 terminals? Two of them get small wires attached to them and the resistance between those terminals is very controlled. If it's a 50 mV shunt for 100 A, then the resistance is 0.050/100. The other HUGE terminals is where you attach your heavy wire.

A Hall effect sensor depends on the current being measured and a fixed magnetic field. This generates a voltage that is signal conditioned. For a 3 dimensional solid that exhibits the properties, the vectors (magnatude, direction) are perpendicular to the edges.

The Digital Panel Meter gets tricky because it's circuitry doesn't like sharing ground hence the need for an isolated power supply.

Yeah I figured it worked similar to that, just did not appear that way. So would I have to worry about my nonstandard 36v if I just go with an analog meter?

No. An analog meter is internally a very sensitive current meter, like 50 uA. it's configured to read a voltage because of a series resistor. Scales are drawn on the meter face for whatever engineering units that are desired. No external power is required. Not sure how well mechanical movements hold up under vibration and humidity.

Like if I found a 50A > analog meter (includes shunt), would it be as simple as hooking it up in series with my motor, and I'm done? Or will I still probably have to use a regulator of some sort?

I gave you one such link for a 100 A analog meter and shunt. Both have to be purchased separately from the same source. No power source is required.

Standard power supply voltages are 5, 12, 15, 24 and 48 V. There are some voltages below 5 V that are becoming standard too. the lower the voltege, the lower the power required to operate. The next set of standards are multiples of the dry cell (1.5 V). Way back when 6.3 VAC, 22.5, 45 and 300 V were standard.

 

[rs14smith]

The SHUNT is a very low value resistor with 4 Terminals. Why 4 terminals? Two of them get small wires attached to them and the resistance between those terminals is very controlled. If it's a 50 mV shunt for 100 A, then the resistance is 0.050/100. The other HUGE terminals is where you attach your heavy wire.

Thanks, I learned something today

What is your take regarding the analog meter, as far as what additional components will be needed other than a shunt?

Like this great one that has the shunt already built in, and it's located in the US!: **broken link removed**

 

[KeepItSimpleStupid]

That will work. This one, https://www.allelectronics.com/make-a-store/item/PMD-100A/100-AMP-DC-PANEL-METER/-/1.html is $25.50 with an external shunt.

take your pick!

 

[Reloadron]

Attached is an image of a 50 Amp 50 mV shunt. Now as we have covered a current shunt like this is no more than a very low resistance, very high power resistor. The image tells us the actual resistance between the sense terminals should be about .001 Ohm. Sure as hell a low resistance huh?

Now, do you have a meter as in a small maybe hand held digital voltmeter that can measure milli-volts? Got a small piece of maybe AWG 12 solid conductor wire, as used in home wiring, like a chunk of ROMEX cable? Making a basic shunt to learn from is pretty easy. A very short length of copper wire in a large gauge like AWG 12 or 10, a meter and a few alligator clips is all you need.

Beyond that, any of the solutions recently linked to will work but making a small home brew shunt would maybe help the learning process.

Remember something. Earlier I asked if you ever plan to reverse polarity (motor direction). If you do it is important to place the shunt upstream from the load polarity switching. This is especially true when using an analog meter designed for unidirectional input.

Ron