Author Topic: Shunt and Meter question (Read 7746 times)

birdhouse · « **on:** October 31, 2009, 10:14:54 AM »

hello all-

i bought an ammeter with shunt from the far east and am a little confused on how to hook it up.

photo link below

i understand the "working power" wires. and i understand that the other two wires coming out of the ammeter are connected to the shunt via the small screws. then there's the "measure input" positive and negative. i would think that the positive wire coming off the rectifier would connect to one side of the shunt, and the other side of the shunt would connect to the positive battery terminal. is this correct? or do both positive and negative wires both run accrossed the shunt so it "bridges between the wires.

sorry to ask such a stupid question. i don't want to fry this thing as it took more than two weeks to get here.

http://www.fieldlines.com/images/scimages/12090/shunt100a.jpg

http://i118.photobucket.com/albums/o112/adrock8/shunt100a.jpg

thanks for any help!

Made title descriptive.TW

willib · « **Reply #1 on:** October 31, 2009, 11:05:33 AM »

Hi birdhouse is there a website where we can find a PDF for this?

birdhouse · « **Reply #2 on:** October 31, 2009, 11:42:41 AM »

will-

no web site, no pdf just an e-bay listing:

http://cgi.ebay.com/3-DC-100A-Blue-LCD-Digital-AMP-Panel-Meter-Shunt_W0QQitemZ250471565903QQcmdZView
ItemQQptZLH_DefaultDomain_0?hash=item3a5144ca4f

if the shunt showed both wires going in/out of it being positive then it would be obvious, but the photo showing pos and neg gets me confused.

he must be getting popular, i bought it now for $20 now its $35... hmmm.

thanks for any help!

hydrosun · « **Reply #3 on:** October 31, 2009, 12:01:58 PM »

The + and - signs are indications of current movement. If the diagram would have put a load or battery to the right of the shunt it would be clearer. If the shunt is in the negative leg from the turbine to the battery, then the - terminal of the shunt is toward the turbine and the + is toward the negative post of the battery.

I've used shunts for analog ampmeters without markings and always have a 50-50 chance of getting the right direction. At least this thing is marked.

Chris

willib · « **Reply #4 on:** October 31, 2009, 12:02:37 PM »

Check his site again ,he must have just changed the drawing.!

you are right though , always shunt in line , he now shows it in the negative line .

birdhouse · « **Reply #5 on:** October 31, 2009, 12:22:22 PM »

will-

as far as i can see, he has no website. all of the responses i get are in very broken english.

chris-

so your saying to connect the entire shunt in the pos line and have the pos on the shunt face the pos on the battery and neg to the rectifier?

anyone to confirm this? (not that i don't trust you chris, just seeing if anyone else has any valuable info).

thanks for the help!

tanner0441 · « **Reply #6 on:** October 31, 2009, 02:39:38 PM »

Hi

Amps are measured in series with the load.... Volts are measured across the load..

If the meter flicks backwards turn it round.

With an amp meter, you are measuring the volts drop developed in the shunt by virtue of its resistance.

Hope this helps

Brian.

scoraigwind · « **Reply #7 on:** October 31, 2009, 02:42:24 PM »

It's probably like a multimeter and in which case the power for the meter has to be distinct from and not connected to the circuit being measured. If so then you may need to keep it supplied with batteries or build an isolated power supply for it that can 'float'.

willib · « **Reply #8 on:** October 31, 2009, 03:42:32 PM »

Birdhouse , not his site, i ment to say the info in his ebay listing has changed

birdhouse · « **Reply #9 on:** October 31, 2009, 05:38:27 PM »

will- what part of the listing has changed? the picture looks the same.

hugh- i think you may be right on the seperate power supply.

chris- i just tried hooking it up the way you suggesting and i almost let the magic smoke out. two of the wires off the meter got orange and burnt up their insulation almost immediately. i didn't even have a chance to put a load on it yet. i'm not blaming you at all. anytime i hook things to a battery not knowing exactly what i'm doing, i accept that i may ruin things. the meter doesn't appear to be ruined though, just need new wires soldered into the old plug. the backlit part still works!

so back to square one. maybe next try i'll use a seperate power source like hugh said. see if it works that way.

thanks for all of the suggestions!

gizmo · « **Reply #10 on:** November 01, 2009, 04:07:27 PM »

Hugh's right, those meters need a isolated power supply. There is a article on my site about using them.

http://www.thebackshed.com/Windmill/articles/PanelMeter.asp

If you have a old unused network card you can use the inverter to provide the isolated power.

Glenn

birdhouse · « **Reply #11 on:** November 02, 2009, 08:08:57 AM »

glenn-

thanks for the info! very nice explanation and diagram! i never knew that was on your site. your meter required 9 volts, so i see how you got that out of the computer chip/regulators/caps/ect. mine will work with anywhere from 7-30 volts. is there an easier way to get "isolated" power from my bank without having to adjust for voltage? i don't have mounds of old chips and electrical parts sitting around, but do have a radio shack close.

thanks

birdhouse

hydrosun · « **Reply #12 on:** November 02, 2009, 10:39:33 AM »

I said to put the shunt in the negative leg. From the negative output of the turbine to the negative post of the battery. The negative marked lug to the negative output of the turbine and the positive marked lug to the negative post of the battery. I did not say to put it in the positive leg. I'm not sure how that got turned around. I don't know why the terminals overheated. I do remember getting a similar led display and the instructions saying it couldn't use the same power as what was being measured. So an isolated power supply is needed as others have written.

Chris

Rover · « **Reply #13 on:** November 03, 2009, 02:56:11 PM »

For testing.. just got to R.Shack and pick up a 9 volt batter snap on battery and connector, wire the shunt as others have said. Once you establish that the meter is ok, you can worry about powering it from another source.

I have one of the similar meters, wired for portability with some banana posts running off a 9 volt battery.

Rover · « **Reply #14 on:** November 03, 2009, 03:06:54 PM »

(blank)

birdhouse · « **Reply #15 on:** November 04, 2009, 08:25:23 PM »

ghurd, glenn, chris, hugh, will and brian-

thanks so much for taking the time to walk an electronically challenged person like myself through all of this.

the original plug was fried, and the wires were 26 awg (so hard to do anything with) so i soldered new and longer 20 awg wires to the existing prongs sticking out the back of the meter. hooked it up like chris said (twice) in the neg leg. hooked the power for the unit to a seperate source, and wow, it works! so then i got greedy, and tried to hook the power for the unit to the same battery i'm using. wow, still works, but the reading vary by around 55 amps. so this thing obviously need a seperate supply as many of you mentioned.

by the way, i'm testing this meter by measuring current being pulled from the battery rather than charging the battery. it is just easier to get it figured out this way. then i hook a harbor freight meter up in the negative line along with the shunt meter, and the HF meter reads around .2 of an amp higher than my new meter. there is a tiny screw on the back. could this be for calibration? i don't even know if it is worth calibrating it to a three dollar HF meter...

i don't know if anyone is still even following such a basic thread, but my next question is if there is a super easy way to trick the meter into thinking it is on a seperate power supply? like i said, i'm not super good with small electronics. could a simple transformer work? if i ran a transformer just for the meter to, say, change 12 VDC to 24VDC, would that do it?

i know glenn gave me a way to do it, but i don't have an old network card and caps around.

maybe it's time i read some books on DC theory.

thanks again!

Rover · « **Reply #16 on:** November 05, 2009, 03:35:09 AM »

What are you trying to measure? I mean what load ? You said "being pulled from the battery".

In my experience .2 Amps difference is within the percentage error of the 100 amp shunt meter. What was the current measurement ?

ghurd · « **Reply #17 on:** November 05, 2009, 05:25:25 AM »

Transformers only work with AC.

Do not try to directly change DC to DC with a transformer.

The $3 HF meters with an un-almost-dead battery are astoundingly accurate. Usually.

Myself, I would not know which meter was wrong. Unless the other meter was high $.

Maybe the other meter needs adjusted?

"A man with 2 watches never knows the time"

G-

birdhouse · « **Reply #18 on:** November 05, 2009, 08:00:34 AM »

rover-

i've just been playing around with the unit. i want to use it to tell me how many amps my turbine is putting into the batteries once it is installed. for now, i've just been making sure it works.

i think the .2 of an amp id fine for this unit. if i end up going 12 volt, this is less than 3 watts. nothing to get my panties in a bunch over.

ghurd-

no it is not high dollar.

i like your analogy of the man with two watches

i do have a few small UPS systems. brand: APC model: ups-es 500. i got them for free, so tearing one apart would not be a big deal. do you think there may be enough electrical bits in one of those to create a isolated power supply to trick my meter into thinking it isn't connected to the batteries it is monitering?

those ups things are pretty cool. you can use them as a battery charger or an inverter! i've been playing around with a little larger unit from APC and found it works really well as an inverter and doesn't need grid power to start up! yay! have a small inverter now for free!

thanks!

willib · « **Reply #19 on:** November 05, 2009, 10:59:25 AM »

Hi birdhouse ,i am very glad to hear that its still working.

What battery voltage does it require to run ,he has a few different ones,the link you gave out said , i think, 6 to 24V , yes?

so why not use a separate supply , like others suggested , you could use 8 AA batteries

for 12V or use a 9V battery?

You would want your power supply to be in the middle of the range if possible,not at the top or at the bottom .

we can determine the best battery for the job if you could measure the current going to the unit when it is on.

ok , the thing is lit up and working ,right,if you break the connection to the unit and insert a meter in line , what is the current going to the thing?

willib · « **Reply #20 on:** November 05, 2009, 11:07:04 AM »

hmmm I should have read your whole last post .

.2 Amps at 12 volts ,huh?

OK

Rover · « **Reply #21 on:** November 05, 2009, 01:45:14 PM »

I'm pretty sure the .2 amps is the difference Birdhouse was seeing between the Shunt and HF meter readings. (don't know at what current he saw the .2 amp diff (Birdhouse?)

Those LCD meter units typically pull about 20 mA w/0 back light and 40-60 mA w/back light to power the unit.

I'd just use a 9 volt battery with a switch between it and the unit to turn the power off. Unless you are going to be staring at 24/7

Rover · « **Reply #22 on:** November 05, 2009, 01:48:22 PM »

I'm pretty sure the .2 amps is the difference Birdhouse was seeing between the Shunt and HF meter readings. (don't know at what current he saw the .2 amp diff (Birdhouse?)

Those LCD meter units typically pull about 20 mA w/0 back light and 40-60 mA w/back light to power the unit.

I'd just use a 9 volt battery with a switch between it and the unit to turn the power off. Unless you are going to be staring at 24/7

birdhouse · « **Reply #23 on:** November 05, 2009, 06:40:56 PM »

will and rover-

thanks again for the help.

yea the .2 amps difference @ 12 VDC was from a HF meter and my new digi amp meter. the unit will take between 6 and 24 volts to power it. i'll take rovers gestimates that it will draw 40-60 mA seeings it IS backlit.

the reason i'm being so intent on not having a seperate power supply is because i plan on using this up at my ranch. it's a three hour drive and i already need to remember lots of things IE: chainsaw, potable water, deer feed, food, beer, water connections for rain barrels, building materials, gas, propane ect.

i don't want to have to remember if my shunt battery is full or not, and if i need to bring an extra. although, now that i think about it, i guess i could use rechargeable 9volts to do the job. and recharge them up there. it just seems like it would be soooo much easier if the meter just ran off the bank. nothing to dink with once it is set up.

thanks!

Rover · « **Reply #24 on:** November 05, 2009, 06:53:38 PM »

Think of it this way... you are eventually going to want to know what kind of power was produced when you weren't there, and it won't take long for you to start thinking that way. This is just an intermediate step.

The next step will be a data logger of some kind, so you can calculate how much over time, how much used, battery bank voltage over time etc.

Trust me.. been there.. now all my data is logged and available on the internet.

FYI... the lcd meters are nice, but only show you what is what , right at that momemt.

birdhouse · « **Reply #25 on:** November 06, 2009, 01:05:09 AM »

rover-

i see your point, and have thought of such things. it would be really nice to be able to log all power from the turbine and solar, battery voltage, wind speed, temp and other such things.

none of my re system is in place yet, but i've got 400 watts worth of solar panels and my turbine is nearing complete for the spring.

doesn't data logging require a computer? my cell phone doesn't even work at my place... i can't imagine any computers up there. it just wouldn't be right.

i just want to be able to watch my turbine at the end of the day and see what it is producing in real time without having to worry about powering an ammeter.

thanks birdhouse

TomW · « **Reply #26 on:** November 06, 2009, 01:51:13 AM »

I use a couple "Doc Wattson" meters. It does real time display of parameters and cumulative data. Amps, watts, volts and peak amps.

I had some issues with the one on the turbines spontaneously resetting itself but not lately.

If you use the 3 wire setup it does NOT need an external voltage source.

Just another option. About $70.

Tom

Rover · « **Reply #27 on:** November 06, 2009, 03:33:22 AM »

Reference for what Tom is talking about

http://www.rc-electronics-usa.com/ammeters/3-wire-meter-connection.html

birdhouse · « **Reply #28 on:** November 06, 2009, 07:21:23 PM »

thanks for the replies!

maybe i'm fighting an uphill battle here. i was hoping to not have to spend the money on a doc watson, and have heard they aren't reliable for their rated capacity, but maybe that is the best solution.

who knows. i'm sure i will have a clearer view once things are running.

all of your folks help has been much appreciated!

birdhouse

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Author Topic: Shunt and Meter question (Read 7746 times)