Voltage/Current Panel Meter Installation

Users who are viewing this thread

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
I bought an electric vehicle awhile ago and had a EVSE (power box to recharge it - Electric Vehicle Support Equipment) installed which has been working great. The box just has simple status LEDs on it, and I was curious about the line voltage and current that was being drawn, so I just got delivery of a panel mount V and A meter. As a sanity check, since it came with absolutely no instructions, I wanted to double-check how to run the current carrying lead through the toroid. I'm pretty sure that I'd only run either L1 or L2 through the coil (toroid), and not both. Is this correct? Do I need to worry about trying to get it to run nice and straight through the coil, or doesn't it really mater? What about the other power lead, do I need to run it as far away as possible in the box, or doesn't it really matter? The ID of the toroid is about 3/4", and we're dealing with 8g power wire, so there's a lot of room for moving it around.

At least on the back of the thing they did label the inputs. The specs on-line indicate it should handle the voltage and current associated with the EVSE with a fair margin.
 

DonL

Jack of all trades Master of one
Messages
5,205
Reaction score
72
Points
48
Location
Houston, TX
If you are not using a Neutral then L1 And L2 should be carrying the same amount of current. And Yes only 1 Conductor should be going thru the core.

You need to make sure the Amp meter has the proper Shunt for your application.

Do you have a link to your New Meters ?


Have Fun.
 

Vegas_sparky

Digital Billy
Messages
486
Reaction score
42
Points
28
Location
LV,NV/ Nowhere,UT
For accurate measurement, pass only one of the line power leads through the coil of the current transformer(trade slang=donut). It doesnt have to be perfect. Do not wrap the wire around the coil. Multiple wraps around the coil will result in the displayed current equaling the actual current x # of passes(wraps) through the coil. The location of the other line conductor in the enclosure doesn't matter.

When installing status/proof circuits we often wrap the coils to ensure an adequate amount of current is "seen" by the donut. For that application a current switch is installed.
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
The meter is an induction reading device, so no shunt is used (it uses the line voltage to run itself and to monitor that as well).
I'm thinking of installing it with an on/off switch. Might get it in today, but if not, soon and I'll put up a picture.
 
Last edited by a moderator:

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
Okay, after a delay, I finally got the panel installed this evening, it shows, on average 243vac, but while I know I've got the coil around one of the power leads...it reads zero amps. I'm charging the car at the moment, so don't want to take the cover off and play with it more right now, but thoughts? With 8g wire in the box, it's a bit tough to move them around, and the wires to the induction coil are probably only 24g, so they could have been damaged when I put the cover on. I may buy a box extension, and then there'd be lots more room.

But, in the meantime, thoughts?
2014-10-29-020.jpg
 

Reach4

Well-Known Member
Messages
38,749
Reaction score
4,400
Points
113
Location
IL
Here are some possibilities that I see:
  • Meter is defective
  • Toroid sense wires are wired to the meter wrong
  • You ran the wrong wire (i.e., the safety ground) through the toroid
 

DonL

Jack of all trades Master of one
Messages
5,205
Reaction score
72
Points
48
Location
Houston, TX
You should look to see if the Shunt is mounted on the Meter board.

The Shunt is optional on a lot those meters, and you put the one that matches your current range.

If the shunt is in your "Probe" you cut or remove the shunt jumper on the board.


The induction transformer could be hooked up on a different phase than the one the meter uses for power reference. Sensing the other phase may work.


You know what you are doing.


Post Pictures of you in your PPE.
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
The meter gets the same 240vac no ground wire, but the coil is only on one lead there and it does not appear to be any place to install a ground on the board (I'll have to look at that more closely when I take it apart again). The entire body of the meter is plastic, so a safety ground may not be required. It would be easy to swap the induction coil to the other power lead, though. I'm going to wait until tomorrow and buy a box extender. The leads to the meter itself are good quality, but not very big gauge and the fuse is 0.5A, and probably could be smaller. The meter had no instructions and does not appear to have any adjustments...a two-wire plug that goes into the board that is attached to the L1/L2 , and a terminal block to clamp in the two leads from the coil. Would have been much nicer if it worked first time!

Thanks for your thoughts.
 

DonL

Jack of all trades Master of one
Messages
5,205
Reaction score
72
Points
48
Location
Houston, TX
Them meters are made in China.

I use them on my battery charger builds, and test equipment.

I can send you docs, if you need them. In Chinese.

The only adjustment on the back of most of the boards is the soldered in shunt.

It may have a V-Adj on the front of the board, but you have to take it out of the housing, And really should be no need to adjust it, if it was calibrated properly.

You should not need a ground, for the meter.

The amp meter side is wired for AC and not DC correct ?

Can you take a picture of the back of it when you open it up ?


Good Luck on your project.
 
Last edited:

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
It's reading the ACV properly, it's just that the ac current readout is showing zero when I know the car is drawing current (and you can see the EVSE's 'charging' lamp is on). One of the wires may have been dislodged when putting the cover on the box. A box extender should put the entire thing above the power lines going through. The board only has four inputs: power (it's obviously getting that, since it's reading vac properly), and two to the coil. It has the proper current range for the load (max 32A), or at least that was what the spec said where I bought it. It was cheap, $20 delivered, but I just wanted a relative indication, and high accuracy was not required. Actually working, though, was part of the requirement! Maybe operator error...I'll take your thoughts and see what I find tomorrow when I take it apart.
 
Last edited by a moderator:

DonL

Jack of all trades Master of one
Messages
5,205
Reaction score
72
Points
48
Location
Houston, TX
Sounds like you have it under control.

Reading the other side of the line may be the key. Because of its phase reference.

The lines going to the coil will work best if Shielded or Twisted, when ran next to other wires.


Good Luck.
 
Last edited:

Vegas_sparky

Digital Billy
Messages
486
Reaction score
42
Points
28
Location
LV,NV/ Nowhere,UT
Phasing should have nothing at all to do with why its not reading. Either hot leg is appropriate.

I'd get a ballpark figure with a clamp on meter, then double check those connections.
 
Last edited:

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
It didn't make sense, on the induction circuit, which leg it was attached to since it effectively just is another ac voltmeter reading the induced ac signal. But, unless the meter itself is also bad, when I put on the box extender (no hassles now with getting the wires positioned just right), I ohmed out the induction coil and it is open. I don't feel like tearing off the insulation and locating the broken wire, but its probably where they attached the external leads from the windings. Since I have no good idea the turns ratio, I'm going to see if I can get a new one. I was hoping that a wire just broke or came loose in the process, but it was not to be. Bummer.
 

DonL

Jack of all trades Master of one
Messages
5,205
Reaction score
72
Points
48
Location
Houston, TX
Sounds like the coil or wire is open.

R X 1k should have a reading.

10:1 and 100:1 is the norm, for many of those small transformers.

Do you have pictures ?


Good Luck.
 
Last edited:

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
This is the meter I bought
I should have a new one on Monday...I'll probably just use the new coil, as the hole was a bit tight, and I don't think it will come out easily, plus, it's power leads are soldered to the on/off switch, but that just plugs into the board)
2014-10-29-019.jpg
.
 
Last edited by a moderator:

DonL

Jack of all trades Master of one
Messages
5,205
Reaction score
72
Points
48
Location
Houston, TX
Normally when I wind a coil like that I use the same type wire that comes out of it. You say the wire type changes ?

Them Connectors that Damage the conductor suck, and make it hard to get a reliable connection. They do make good test points, But can damage small wire like that, or not even make a good connection.

There should be 2 holes beside them and you can solder the wires directly to the board.


Good Luck on your project.
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
The coil has tape wrapped over it, so the only wires visible are those sticking out to make the connection. I have a whole new unit being delivered Monday and I'll send one set back (already have the return authorization). So, don't really know if there's different wire, but it's definitely open.
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
Well, update...the replacement's coil is open too, and yes, I do know how to use a DMM on ohms! Very annoying. I don't want to untape it all and try to wind my own, as it would be tedious to try to calibrate the meter (wonder how they did that with a bad coil in the first place!). Don't expect fantastic accuracy at the price, but it should at least not be open! Maybe a bad batch and the next one will be bad, too. Ugh!
 

DonL

Jack of all trades Master of one
Messages
5,205
Reaction score
72
Points
48
Location
Houston, TX
Well, update...the replacement's coil is open too, and yes, I do know how to use a DMM on ohms! Very annoying. I don't want to untape it all and try to wind my own, as it would be tedious to try to calibrate the meter (wonder how they did that with a bad coil in the first place!). Don't expect fantastic accuracy at the price, but it should at least not be open! Maybe a bad batch and the next one will be bad, too. Ugh!

That is a bummer.

Maybe there is a capacitor in series with the coil under the tape ?

Can you measure any AC voltage on the coil when current is going thru the coils core ?


Good luck on your project.
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
Don't think there's a cap in there. If there were, the ohmmeter would show something as it charged the cap. I didn't try to install this one. I guess I could, but I expect it to operate in the same manner. I can't rationalize why an induction coil would have a cap in it, though. The tape on it does not really show any lumps where a cap would be except where the external leads go under the tape/insulation on the thing.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks