Forum Discussion
- The meter is nice - looks sharp and offers good features. . . .however : If you need to do any troubleshooting (like maybe check why the WH ain't cooking) you need something that's small and portable. This meter is almost useless for those instances. Need to buy one or 2 Harbor Freight specials for $3 each to supplement this.
pianotuna wrote:
Hi OnaQuest,
I'm sure you did not mean it--but your post sounds a bit aggressive.
Just to set the record straight the Hall Effect meter shows positive and negative flow of amps.
It is rather neat to see the solar system sending energy to the chassis and lowering the load on the alternator.
I already have a volt meter (two, actually). I'm just offering options.
No offense or aggression meant, Pianotuna.
I simply wanted to point out, for the OP's benefit, that there was more function available in the unit being discussed (for nearly the same money) than in a single amp meter. (Shunt or Hall effect technology not withstanding.)
The physical installation of the DC resistive shunt may be more difficult (labor intensive, cable logistics, etc.), but the electrical implementation is not any more complicated.
The DC shunt works well with my simple TriMetric installation.bigcitypopo wrote:
hmmm.. do you guys have pics of your stuff, and how your wiring works... this stuff is kinda new to me. Am I over thinking it?
The installation of this meter really consists of 4 parts.
1. Mount the meter where you want it.
2. Install the shunt. The photo Mark posted shows the shunt. One end of it goes directly to ground. The other goes to the negative lead from the battery, which previously went to ground. Note that the shunt is not insulated so you have to figure out some way to mount the shunt so the ungrounded end is insulated from ground. It could be simple or not depending on the wiring of your battery. In my case the battery is under the floor in a plastic battery box. The wiring is exposed to everything kicked up by the tires. I mounted the shunt in a plastic box mounted to the ground stud used by the battery negative lead.
3. Connect the battery negative lead to the ungrounded end of the shunt.
4. Run the supplied 7 wire cable from the battery positive, the ground end of the shunt, the hot end of the shunt to the meter.
When I installed my ammeter I found the most challenging part was installing the shunt. YMMV- I try to install a T Fuse rated at least 10% fewer amperes than the rating of the shunt. The reaction time of the fuse is impressively fast.
bigcitypopo wrote:
let me know what ya think. pretty straight forward, no?
If cost wasn't part of the equation, I'd suggest that you choose a Trimetric. They're well proven, made in the USA, offer very useful serial data output, and Bogart Engineering provides outstanding customer service.
But... cost is always part of the deal and that combo meter on Ebay looks really cool! I'd spend ~$40 just to have one to play with for a while. I'll add that I bought the volt/ammeter that's in my truck (see pics) from this exact same Ebay seller and the transaction was trouble-free. The meter works great and was the only one I could find that did what I needed it to do in the space I had available.
Both of my panel-mounted ammeters use current shunts, although I do have a Fluke DVM that uses a Hall effect sensor... Shunts are a well proven analog technology, they're calibrated (and as a result are very accurate), and are more than capable of handling the current they carry (ie. will NOT ever "burn out" when installed correctly). They are half the cost (or less) than a comparable hall effect sensor/meter combo. In my installations, they are each mounted within inches of the negative terminal of the batteries they're monitoring. IMHO, the only downside of a shunt is that, to maximize accuracy, you have to use extra care to ensure the lowest possible resistance at the Kelvin connections. My point is; If the meter provides the data you're looking for, it does not matter which current measurement scheme you use for an RV/automotive application.
Cheers
-Mark
- Hi Salvo,
Not into scare tactics. Just revealing my own thought processes. You are right a 500 amp shunt is unlikely to burn out--until some one does something stupid such as shorting the input to a large inverter.
The usual derating for shunts was 66% when I researched them. My hall effect meters seem to agree very well with a high end fluke ammeter. They may be less accurate--and the DC ones I use do stop at + or - 70 amps.Salvo wrote:
If you abuse any meter it will burn out. Your scare tactics are not valid. This is a 500A shunt! You need in excess of 500A for a fairly long time to burn this shunt.
In general, if a shunt does blow, it's the the fault of the shunt but the person who installed it. Shunts must be derated by 50%. If maximum current in a shunt application is limited to 50A, then use a 100A shunt. In the OP's case the shunt is rated 500A. It's overkill, but it will never blow. The battery in-line fuse will blow first.
As far as using shunts vs. hall effect, I believe shunts have more accuracy and can measure small currents.
BTW, that looks like an excellent meter. Go for it!
Salpianotuna wrote:
I don't like the shunt because it IS possible for it to burn out. - wow, looks like it should do the trick to monitor loads through my inverter as it has the shunt. I have the inverter wired separate from my solar controller because of the amperage draws. I can monitor all other trailer loads through the solar controller. This compliments the rest of the system and it adds to the "blink and whir" factor!
Please let us know how it performs. - If you abuse any meter it will burn out. Your scare tactics are not valid. This is a 500A shunt! You need in excess of 500A for a fairly long time to burn this shunt.
In general, if a shunt does blow, it's the the fault of the shunt but the person who installed it. Shunts must be derated by 50%. If maximum current in a shunt application is limited to 50A, then use a 100A shunt. In the OP's case the shunt is rated 500A. It's overkill, but it will never blow. The battery in-line fuse will blow first.
As far as using shunts vs. hall effect, I believe shunts have more accuracy and can measure small currents.
BTW, that looks like an excellent meter. Go for it!
Salpianotuna wrote:
I don't like the shunt because it IS possible for it to burn out. - The main reason for using a shunt instead of a hall effect sensor is cost.
The cost of making a shunt is only a few cents, whereas the cost of a hall effect sensor (1,000 piece price from Analog Devices) is $2.47. Add the cost of the additional components and the retail price for the hall effect meter would be about $40 more than the shunt meter.
When using a shunt meter, the shunt should be installed as close to the battery bank as is possible; this reduces the IR drop in the wiring. The wires going to the meter can be quite small because they carry very little current (µAmps).
With a hall effect meter, it is sometimes necessary to use shielded wire for the connecting wires. - Hi bigcity,
Here is a picture of a hall effect set up.
Here is a picture with a shunt instead.
I don't like the shunt because it IS possible for it to burn out. My understanding is that when that happens since the shunt is in series within the circuit that there will be no power until you jumper around the failed shunt. This is no fun at all at -40. So, if you decide on going with a shunt, make sure it is an accessible location.
I currently use four hall effect sensors in my RV. Two for 12 volt and two for 120 volts. Because of the "donut", with four sensors (and the appropriate switches), I am able to monitor 3 circuits on the DC side and 3 shore power cords on the AC side (the OEM 30 amp and two auxiliary cords).
