# Ammeter questions



## e_canuck (May 8, 2008)

Hi all.

I have been testing/playing with my new ammeter.

It is a 500A gauge.

With no load it displays -2A.










At first I tought it was the drain from the gauges themselves. They run off the same battery.

But the are connected prior to the shunt. No influence. Right?
The -2A is consitent. As I add an remove loads, it doesn't seem to vary.
My charger is a 2A. When I connect it, the display read -4A.










That one is with my motor running.

Now there is an ajustment on the gauge. But I think the gauge is probably at its most imprecise at 0A and best at 500A. You can't break stuff with no Amperage.

Plus I have no idea how you can calibrate the top end of the range.
On an analog gauge you probably can't see 2A. And I would be happy.

So my feeling is to live with it.

What do you guys with digital gauges or brains or both think of this? Any opinion?

Thank you in advance,

DP


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## ww321q (Mar 28, 2008)

I haven't been very happy with most test equipment I have used . The latest that I can think of is the hand held pyrometers . I discovered that as you hold it in your hand the reading will start to change . So the ambient temperature that you stored your meter in will also effect the reading . I would think that 1% ain't that bad on a 500 amp ammeter . J.W.


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## Chris Sandberg (Sep 13, 2008)

Hello DP, I am no expert and I don't know anything about the digital stuff but does the - sign maybe mean the polarity is backwards. Also do you have a external shunt or is it built into the box if it is it may need to be set for the voltage of your system and the amps you are wanting to read. Just some ideas from a newbie/ beginner best of luck.
Chris


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## e_canuck (May 8, 2008)

Thanx ww321q,

I tend to agree. My setup is in the garage at freezing point so temperature might prove to be a factor.




Chris Sandberg said:


> Hello DP, I am no expert and I don't know anything about the digital stuff but does the - sign maybe mean the polarity is backwards. Also do you have a external shunt or is it built into the box if it is it may need to be set for the voltage of your system and the amps you are wanting to read. Just some ideas from a newbie/ beginner best of luck.
> Chris


Hi Criss,

Polarity would affect it. Reversing the wires, on the shunt, would reverse the results.

On the first picture you can see the minus on the second with the motor running it is positive. I have used some automotive bulbs while testing and I can get it to show zero with only one bulb. Draws about 2A.

Right now I think a display of 35A, probably is 37A.

The shunt is external. If you look at both pictures you can see it. It is screwed directly to the negative post of the battery with a contactor screwed to it. ( for the motor )

I have tough of running the gauge the other way so driving would show negative amps and charging positive. But seing a negative load would be to peculiar for me.

Thankx all, I will live with it the way it is.

DP


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## Jimdear2 (Oct 12, 2008)

e_canuck said:


> Thanx ww321q,
> 
> Thankx all, I will live with it the way it is.
> 
> DP


I'm supprised that there is no provision to zero the meter. 

I'm not an electronics guy but I would think there should be an adjustible something somewhere. No little tiny screw or pot on the back of the gauge?

Otherwise I'm sure one of the electronics wizards could tell you how to add a trim resistor to the circuit.

Be good


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## fugdabug (Jul 14, 2008)

If you are using a shunt, (largish brass cubes with four or five brass plates two bolts on top and two small screws with washers on the base all mounted on a bakelite mounting base...) the two leads would come off the shunt at the two small screws, the 'positive' side is fused normally (1Amp in-line fuse), and the negative not... but arranging which goes where can confuse... so as a rule of thumb, I put the negative on the screw towards the most 'pack-wards', and the positive on the side leading to the contactor/controller... Now being you are digital you may not need the fuse (check the product brochure/info material... or look online if the company has a website).
Works for me... even in the cold.


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## e_canuck (May 8, 2008)

Jimdear2 said:


> I'm supprised that there is no provision to zero the meter.
> 
> I'm not an electronics guy but I would think there should be an adjustible something somewhere. No little tiny screw or pot on the back of the gauge?
> 
> ...


Hi Jimdear2.

There is a screw on it but I do not want to touch it whitout instructions from one of the wizards.
Ajusting the zero might work but what about the top end? (500A) There is only 1 screw.

2Amps over a 500A gauge is probably good enough. It just look goofie to show -2A when you know there is nothing there.

The gauge should zero almost every time the car is coasting or stopped.
I am thinking of having a bulb or two on the circuit to make it "show" zero .

Come to think of it there will be the DC-DC converter. So there will always be a positive load .




fugdabug said:


> If you are using a shunt, (largish brass cubes with four or five brass plates two bolts on top and two small screws with washers on the base all mounted on a bakelite mounting base...) the two leads would come off the shunt at the two small screws, the 'positive' side is fused normally (1Amp in-line fuse), and the negative not... but arranging which goes where can confuse... so as a rule of thumb, I put the negative on the screw towards the most 'pack-wards', and the positive on the side leading to the contactor/controller... Now being you are digital you may not need the fuse (check the product brochure/info material... or look online if the company has a website).
> Works for me... even in the cold.


Hi fugdabug.

I have my test rig setup just as you describe it. After reading you post I went back to the diagrams. I am setup like the diagram but there are no fuses anywhere on it .

I was going to fuse only the power side of the gauge . But now I will put fuses on the input wire as well. Cannot hurt. Thanks .

Take care,

DP


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## jlsawell (Apr 4, 2008)

e_canuck, I have the EXACT same setup as yours, but my display box is grey, not black.

I even have the same strange readouts, although I must admit to testing the setup on a small lawnmower electric motor, as my ImPulse 9 hasn't arrived yet.

I think we just have to live with it. I was planning to test the car for a week or so and then put 2 stickers on the readouts. "Do not exceed 400" on the Ammeter and "Do not allow below 50" on the voltmeter" should serve as a reminder to take it easy on the throttle and get home before I get below 50%


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## elevatorguy (Jul 26, 2007)

Sometimes you can get stray voltages that will affect the meter, some fixes are twisting the wires that go to the shunt or a twisted shielded pair with only one end grounded to prevent ground loop noise problems.
If you disconnect the meter leads from the shunt and connect them together what does it read?
if it is 000 then the meter is ok.


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## fugdabug (Jul 14, 2008)

e_canuck said:


> Hi Jimdear2.
> 
> There is a screw on it but I do not want to touch it whitout instructions from one of the wizards.
> Ajusting the zero might work but what about the top end? (500A) There is only 1 screw.
> ...


No, I only fuse the power (into the guage) side. The neutral pole doesn't need it...


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## e_canuck (May 8, 2008)

jlsawell said:


> e_canuck, I have the EXACT same setup as yours, but my display box is grey, not black.
> 
> I even have the same strange readouts, although I must admit to testing the setup on a small lawnmower electric motor, as my ImPulse 9 hasn't arrived yet.
> 
> I think we just have to live with it. I was planning to test the car for a week or so and then put 2 stickers on the readouts. "Do not exceed 400" on the Ammeter and "Do not allow below 50" on the voltmeter" should serve as a reminder to take it easy on the throttle and get home before I get below 50%


Hi jlsawell.

That is too funny.

We are on opposite side of the planet. You are starting summer.

I whent back to your blog and shure enough, there they are .
My shunt is different because it came from a different manufacturer. Long story.

BTW I loved those Darwin Drivers. And I don't mean they are from Darwin Australia.



elevatorguy said:


> Sometimes you can get stray voltages that will affect the meter, some fixes are twisting the wires that go to the shunt or a twisted shielded pair with only one end grounded to prevent ground loop noise problems.
> If you disconnect the meter leads from the shunt and connect them together what does it read?
> if it is 000 then the meter is ok.


Hi elevatorguy.

After reading your post I shouted "to the Batcave!" and twisted the wires using my old hand drill. No effect.

The gauge read zero with both wires disconnected or touching.

Well -2 is the new zero and I will live with it.

Now my next step is to install my box and shunt in the "donor car".
It still run on fossil fuel. And find out how big a DC-DC converter I need.

Thanks all.


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## elevatorguy (Jul 26, 2007)

well that is odd, kinda hoped that would have done it. You can make a small resistor divider to correct it if it really bugs you.
Or like you said -2 is the new zero


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## e_canuck (May 8, 2008)

Hi guys. And gals if any present.

Quick update.

If I connect the ammeter directly to the shunt, without any aligator clip, it now read -1A. ( A bit of a pain as the pig tail is only 5 inches long )

Changing the clip on the input- for any other ones, from my collection, I can make it read anything from -1A to -150A. ( Crapy testing equipment or what? )

Also that gauge is powered from the same battery it is monitoring. The DC- and the Input- seem to talk to each other. ( The resistance between them is not zero )

If I power the gauge from a different battery it read ZERO.

Conclusion: I am more than satisfied that the "thing" is good enough

Thanx all,

DP


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## TheSGC (Nov 15, 2007)

e_canuck said:


> Hi guys. And gals if any present.
> 
> Quick update.
> 
> ...


Your meter (Volt or AMP) should not be powered by the source it is supposed to be monitoring. Not only will the values show up wrong, damage could be caused to the meters. You should power the meters with your 12 volt aux battery, or even a 9 volt battery.


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## e_canuck (May 8, 2008)

TheSGC said:


> Your meter (Volt or AMP) should not be powered by the source it is supposed to be monitoring. Not only will the values show up wrong, damage could be caused to the meters. You should power the meters with your 12 volt aux battery, or even a 9 volt battery.


Hello The SGC.

I know, but this one is sold as being able to. That is why I bought it in the first place.

This is the wiring dia gram they sent me for the ammeter.
http://www.e3b6a5y.com/365/WiringDiagrams/365-5035LCD-10-500Adc.jpg

and the one for the voltmeter for good measure.
http://www.e3b6a5y.com/365/WiringDiagrams/365-5035LCD-2-2000Vdc.jpg

So they can work of the same battery. I proved it. But you are right there is an influance. I proved that too...

DP


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## TheSGC (Nov 15, 2007)

That diagram is kind of sketchy. Look at the last diagram on both pics. While it *can* be connected to the same source (when it's 20v or lower) I definitely would not do it. 

I am pretty sure if you connect more than your 12 volts for testing (I think that was 12 volts I saw on the screen) and have this meter still connected to the pack you will fry it, even if you only use a single 12 volt battery from the pack for power.

From my own experience (and electrical engineering work) anything smaller than a box of Twinkies probably isn't isolated and has some connections between it's "high" voltage sections and "low" voltage section. 

I just want to warn you and make sure you use a separate power source for those meters, cause I would hate to say "told you so", but I wouldn't do that cause I only do that at work. 

I really need to look into getting a few volt meters.

BTW your bench test setup is AWESOME. I love the meters in the box.


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## e_canuck (May 8, 2008)

TheSGC said:


> That diagram is kind of sketchy. Look at the last diagram on both pics. While it *can* be connected to the same source (when it's 20v or lower) I definitely would not do it.
> 
> I am pretty sure if you connect more than your 12 volts for testing (I think that was 12 volts I saw on the screen) and have this meter still connected to the pack you will fry it, even if you only use a single 12 volt battery from the pack for power.
> 
> ...


Hello Again.

Tanx for the compliment and the warning.

Now I am reading that line in a new light, more like a warning....

There is a connection/interaction between the DC- and Input-. If I disconnect the DC- from the gauge, the display still works, out of range is diplayed and the light is off. Still...

Are you suggesting I power the gauges from a totaly independent source like a 9V batt. or the accessory battery. My plan was to use the cars 12V ( Accessory batt. ) and a DC-DC converter.

DP


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## TheSGC (Nov 15, 2007)

e_canuck said:


> Hello Again.
> 
> Tanx for the compliment and the warning.
> 
> ...


The 12v accessory battery would be the best place to hook up the meters. the 12v batt isn't part of you traction pack that you are measuring and that's a good thing.


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## ww321q (Mar 28, 2008)

I was just thinking , maybe it may be off by 2 at 500 amps . So the actual range is 504 amps . Off by 2 at the bottom and off by 2 at the top and right on in the middle range of 250 amps . I think I would leave it alone . J.W.


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## e_canuck (May 8, 2008)

ww321q said:


> I was just thinking , maybe it may be off by 2 at 500 amps . So the actual range is 504 amps . Off by 2 at the bottom and off by 2 at the top and right on in the middle range of 250 amps . I think I would leave it alone . J.W.


Hi.

For shure an exact number like 500 cannot append. It as to be more or less. I mean: it was made by people.

You probably heard about those cars made the day after the Super Bowl?

Got some extra bits-and-pieces. The gauge box is going in the ICE on the weekend.

That will be one part down, a gazillion more to go.

DP


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