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Painless
07-25-2008, 09:16 PM
Whilst visiting Home Depot / Lowes etc for other bits and pieces, I've also been looking around for a multimeter that I can use to reliably monitor the DC current amps etc on my unit, once it is built and in the testing phase, however, the best ones I can find only seem to go to a maximum current of 10 amps DC. I'm hoping to find a multimeter that will measure up to 30 odd amps, but won't break the bank.

Can any of the electronics guru's recommend a source?

dennis13030
07-25-2008, 11:42 PM
Hi,

My name is Dennis and I am an electronics engineer. The low cost and high current way to go is this;

1. Buy a cheap digital multimeter(the max current rating is NOT important). Believe me on this.
2. Buy a current sensing resistor. See this link. It is a 0.005 Ohm, 7 Watt resistor and it's real cheap($4.16).
http://www.mouser.com/Search/ProductDetail.aspx?qs=IQQypbyqmm0qLPKYZDPMxg%3d%3d
3. Put this resistor inline with the +12V against the electrolyzer.
4. Use the voltmeter to read the voltage across the sense resistor. Whatever value is displayed, multiple it by 200 for the true current value. This calculation is due to the resistor being 0.005 Ohms.

This gets your cheap DMM an effective maximum current measurement of about 37 Amps.

Painless
07-26-2008, 01:53 PM
Cool! That's an interesting idea.

I've been thinking about it and I will be wanting to install some kind of amp gauge in the inside the vehicle, once the installation is complete, so I might just go ahead and buy a suitable in-vehicle gauge and use that whilst testing instead. Would save money in the long run.

Omega
07-26-2008, 02:26 PM
Wow dennis, you are one smart cookie!! :D:D:D

BAD MEDICINE
07-26-2008, 02:32 PM
Id say my biggest weakness in this venture is understanding/measuring the data. Makes me wish I would have made more of an effort to learn it in school.

Painless
07-26-2008, 02:51 PM
I just ordered an automotive amp gauge online from SunPro, it runs +/- 60 amps max which should be ideal. I know that the maxigen systems are pulling well over 40 amps on their setup on a ram just like mine (even same year), so I'm considering working up to that kind of production.

computerclinic
07-26-2008, 03:25 PM
Dennis, is there a gauge that I can connect to my laptop to see more than 1 reading and track the voltage, wattage and amperage? I t would be cool to plot the time, temp, and electric stats on a chart so as to get the best results with the cells...

dennis13030
07-26-2008, 07:40 PM
Dennis, is there a gauge that I can connect to my laptop to see more than 1 reading and track the voltage, wattage and amperage? I t would be cool to plot the time, temp, and electric stats on a chart so as to get the best results with the cells...

First of all, thanks to everyone for the compliments. Electronics is what i went to school for and I'm pretty good with it.

I will try to find this for you. I know they exist. It's a matter of how much $$$ and the spec.s you want. Give me a couple hours.

dennis13030
07-26-2008, 08:08 PM
Dennis, is there a gauge that I can connect to my laptop to see more than 1 reading and track the voltage, wattage and amperage? I t would be cool to plot the time, temp, and electric stats on a chart so as to get the best results with the cells...

Ok, I'm back.

This is the same kind of automated testing setup that I want to do. It is also the same kind of equipment and procedures that I used to do at an old job of mine.

To setup for automated testing including;
1. Source voltage measurement,
2. Source current measurement,
3. Temperature measurement,
4. Output flow rate measurement.

would require a large investment(about $5000 for equipment) and a significant amount of time/effort.

The power is Watts are calculated from the current and voltage measurements.

I would not go this route because there is a better way. My old work does this stuff already.

Let me know what you think.

computerclinic
07-26-2008, 10:25 PM
wow...5K is a bit steep for my wallet, but it would certainly be worth having if it will do all the plotting, especially in a nice graphic...Does it include the PC laptop? Lol

dennis13030
07-27-2008, 01:12 AM
wow...5K is a bit steep for my wallet, but it would certainly be worth having if it will do all the plotting, especially in a nice graphic...Does it include the PC laptop? Lol

Like I said, the better way to go is through my old company. I think it would be cheaper and faster. You would need to supply them with a Request For Quote(RFQ) first to iron out how much $$, deliverables, schedule and details. Materials-wise, you need to supply the electrolyzer for the duration of the testing.

I'm pretty sure that the price would be a lot cheaper.

Blinger101
07-27-2008, 02:04 PM
I hate to butt-in here, but if you're still looking for an alternative to measuring the amperage, you could always make a shunt-resistor:

http://www.youtube.com/watch?v=65EiiE4NoDI

reuk.co.uk/Make-a-Shunt-Resistor.htm

Dennis, since you're the electronics wizz, is the resistor-shunt a viable option for our purposes?

BoyntonStu
07-27-2008, 03:18 PM
wow...5K is a bit steep for my wallet, but it would certainly be worth having if it will do all the plotting, especially in a nice graphic...Does it include the PC laptop? Lol

Do you have 50 cents?

1,000 feet of #10 wire has a resistance of almost exactly 1 ohm.

Buy 1 foot and a half of #10 solid copper wire.

Run your current through the wire.

Take your multimeter and place your leads 12" apart on the wire.

Read amps in milli-volts.

10 milli-amps = 10 amps.

I use it all the time.

BTW You can bend the wire into a wiggle and mount it on a piece of plywood to save room.

BoyntonStu

dennis13030
07-27-2008, 05:10 PM
I hate to butt-in here, but if you're still looking for an alternative to measuring the amperage, you could always make a shunt-resistor:

http://www.youtube.com/watch?v=65EiiE4NoDI

reuk.co.uk/Make-a-Shunt-Resistor.htm

Dennis, since you're the electronics wizz, is the resistor-shunt a viable option for our purposes?

This is a home made sense resistor with a resistance value of 0.001 Ohms. He did a good job on it. Notice the thick wire that handles the high current. The thin wires are for the voltage measurement. My opinion is that you can use this method but it is cheaper and easier to use a real sense resistor.

computerclinic
07-27-2008, 10:54 PM
Its all good advice guys, thank you very much...
I am a computer pro and am looking to take advantage of the cars computer, too. It is still out of my leauge though. I work with PC and MAC not automotive...The digital multimeter that I am using gives me good info on the bench, but what I would like to get a hold of, or even build, is a means of collecting real time info that can be plotted in a graphic format automatically. Info such as the elecrical measurements, temps and gas production,...while also monitoring the vehicle and weather conditions...sounds very involving, but when I think about mini weather stations and how they work with a PC, it makes me believe that there must be a way to collect the info and plot it without needing to take manual measurements every minute or so....

I dunno...maybe its wishful thinking, but I would like to have that sort of info so I can better all of the generator design elements...

dennis13030
07-27-2008, 11:07 PM
Its all good advice guys, thank you very much...
I am a computer pro and am looking to take advantage of the cars computer, too. It is still out of my leauge though. I work with PC and MAC not automotive...The digital multimeter that I am using gives me good info on the bench, but what I would like to get a hold of, or even build, is a means of collecting real time info that can be plotted in a graphic format automatically. Info such as the elecrical measurements, temps and gas production,...while also monitoring the vehicle and weather conditions...sounds very involving, but when I think about mini weather stations and how they work with a PC, it makes me believe that there must be a way to collect the info and plot it without needing to take manual measurements every minute or so....

I dunno...maybe its wishful thinking, but I would like to have that sort of info so I can better all of the generator design elements...

I know electronics but not mechanical stuff and car sensor stuff.

The items required to do the measurements in an automated fashion are;
1. A high current digital power supply that has a suitable PC interface.
2. A digital temperature sensor that has a suitable PC interface.
3. A digital flow meter that has a suitable PC interface.
4. A personal computer.
5. A custom program that has command/status capabilities over the equipment.

My old work has all of this except #3. They are flexible enough to get this equipment too. They sell their testing services.

Dewayne
07-28-2008, 12:53 AM
I got a 30A meter off of eBay for $10. This is a bench type meter and not a car type. I found the car type meters are not marked in single amp readings.

dennis13030
07-28-2008, 03:44 AM
I got a 30A meter off of eBay for $10. This is a bench type meter and not a car type. I found the car type meters are not marked in single amp readings.

Please post a link of this amp meter.

Dewayne
07-28-2008, 07:35 AM
Here is the eBay item number : 130240497876

ridelong
07-30-2008, 08:24 AM
Harbor freight sells a digital multimeter with a 10 amp scale for $3.99.

Works at 20 amps for a few seconds.

I bought 5 to use around the house.

fly
08-09-2008, 07:52 PM
Hi,

My name is Dennis and I am an electronics engineer. The low cost and high current way to go is this;

1. Buy a cheap digital multimeter(the max current rating is NOT important). Believe me on this.
2. Buy a current sensing resistor. See this link. It is a 0.005 Ohm, 7 Watt resistor and it's real cheap($4.16).
http://www.mouser.com/Search/ProductDetail.aspx?qs=IQQypbyqmm0qLPKYZDPMxg%3d%3d
3. Put this resistor inline with the +12V against the electrolyzer.
4. Use the voltmeter to read the voltage across the sense resistor. Whatever value is displayed, multiple it by 200 for the true current value. This calculation is due to the resistor being 0.005 Ohms.

This gets your cheap DMM an effective maximum current measurement of about 37 Amps.

Whoa, I was looking for exactly that... Didn't think of that at all although it makes perfect mathematical sense.
Thanks Dennis, I will definitely try it out... Need to measure current WAY stronger than 10 amps which is the max my amp meter is rated for (although it displays up to 19.9 amps).

Thanks! should have thought of it, but hey, I'm no electronician, just a hobbist!

c02cutter
08-09-2008, 08:47 PM
If you plan on doing any testing at all, and plan on using it in the furture, buy a fluke!

BoyntonStu
08-09-2008, 09:59 PM
If you plan on doing any testing at all, and plan on using it in the furture, buy a fluke!


Not unless you are willing to accept "fluke" readings with a non-Fluke meter.

BoyntonStu

AzDad
08-09-2008, 11:20 PM
Dennis-i have a multimeter does not have a amp reading on it , but it does have a millie amp . How would you convert the reading? Thx Tim

dennis13030
08-10-2008, 10:39 PM
Dennis-i have a multimeter does not have a amp reading on it , but it does have a millie amp . How would you convert the reading? Thx Tim

Is it a digital multimeter and will it read voltages in the millivolt range?

HHO King
10-06-2008, 07:40 PM
Whilst visiting Home Depot / Lowes etc for other bits and pieces, I've also been looking around for a multimeter that I can use to reliably monitor the DC current amps etc on my unit, once it is built and in the testing phase, however, the best ones I can find only seem to go to a maximum current of 10 amps DC. I'm hoping to find a multimeter that will measure up to 30 odd amps, but won't break the bank.

Can any of the electronics guru's recommend a source?

I would recommend a unit like this. I saw it at Extreme HHO.

http://www.extremehho.com

sheriffav8r
10-07-2008, 07:35 PM
I'm going to get this one for HHO and around the house/car:

http://www.sears.com/shc/s/p_10153_12605_03482369000P?keyword=3482369&sLevel=0

Not bad at $60 for 400A AC/DC.... Plus a nice temperature probe, to boot!