FreddyS
Well-known member
Have a 30 amp electrical system in my rig. Need to buy a multimeter to test when I go out, including the shoreline plug. I have seen some really cheap ones and some really expensive ones. Any recommendations?
Multimeters
- Thread starter FreddyS
- Start date
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Larry N.
Well-known member
A $5 special at Harbor freight will work as well, for general RV use, as those costing $hundreds.
OP
OP
FreddyS
Well-known member
Larry N. said:
Man, I bought one of those and tested it against my buddy's really nice one the readings were way off. I don't expect perfection but I want it in the ball park for sure! And I don't think the $ 5 dollar one evens tests at 30 amps and I need this to test shoreline power source.
DonTom
Well-known member
Exactly what are you trying to test or check?FreddyS said:
If it was "way off", by any chance were you checking the voltage from an inverter?
Perhaps you really want something like this, that checks line freq, true RMS AC voltage and such. Simply plug it in to any AC outlet, will check all inverters, line AC and such. I have such in my RV.
-Don- Reno, NV
Alfa38User
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- Joined
- Oct 4, 2007
- Posts
- 6,678
The real cheapies operate just as you observed but... A reasonable one from Radio Shack, or perhaps the big box hardwares will cost around 25-30$ and be pretty good. Watch the amperage limits if you wish to use the amperage scale, most (?) will not do more than 10-15 amps AC.
OP
OP
FreddyS
Well-known member
Alfa38User said:
Thanks! The ones that test amps up to 30 are pricey for the most part. I found some that test to 20 amps in the 20 to 30 dollar range.
carson
Well-known member
Were you thinking of measuring the total 120 V amperage as drawn from the pedestal ? Not easy and not suitable with a multi meter. I don't think anyone does that unless you have a heavy duty measuring system built into the RV.
Just curious....... why are you trying to read amps? The only way that you can load test for total amps is with a shunt. I'm not sure what you are trying to accomplish but I think what you really need to check is voltage. As long as you are receiving 105+ volts under load (>125V no load), you should be fine.
If you are using a meter that clamps around the wire, that reads the amount of amps that you are currently consuming. That's really pretty useless info on 110V from the campground.
Now, if you are dry camping and trying to determine amperage use from your 12V DC system, that's a different story. That is useful info but it takes a special meter that reads DC amps. Run of the mill multimeters do not read DC amps.
If you are using a meter that clamps around the wire, that reads the amount of amps that you are currently consuming. That's really pretty useless info on 110V from the campground.
Now, if you are dry camping and trying to determine amperage use from your 12V DC system, that's a different story. That is useful info but it takes a special meter that reads DC amps. Run of the mill multimeters do not read DC amps.
Lou Schneider
Site Team
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- 13,256
The way to test 30 amp (or 50 amp) power is with a clamp-on ammeter.
Yes, I linked to one available at Harbor Freight. I have a couple of these scattered around the RV and workplace, and they are accurate when compared to professional units. While it also tests voltage and resistance through the clip leads, it only reads out to the nearest volt. This is fine for 120/240 volt use, but not fine enough for 12 volt uses.
Sears has an AC/DC clamp-on meter, but it's tricky to get accurate readings on DC circuits.
One place most meters will disagree is on modified sine wave power like an inverter produces. Here you need a true RMS reading meter, and they run a couple of hundred dollars.
To use a clamp-on meter, you have to be able to clamp the probe around a single wire - either inside the power panel or by making a break-out cord, with separate wires you can get the clamp around.
Trying to run 30 amps through the thin test leads, banana plugs and an internal shunt on a multimeter is asking for trouble.
Yes, I linked to one available at Harbor Freight. I have a couple of these scattered around the RV and workplace, and they are accurate when compared to professional units. While it also tests voltage and resistance through the clip leads, it only reads out to the nearest volt. This is fine for 120/240 volt use, but not fine enough for 12 volt uses.
Sears has an AC/DC clamp-on meter, but it's tricky to get accurate readings on DC circuits.
One place most meters will disagree is on modified sine wave power like an inverter produces. Here you need a true RMS reading meter, and they run a couple of hundred dollars.
To use a clamp-on meter, you have to be able to clamp the probe around a single wire - either inside the power panel or by making a break-out cord, with separate wires you can get the clamp around.
Trying to run 30 amps through the thin test leads, banana plugs and an internal shunt on a multimeter is asking for trouble.
That's why I am curious what the OP is trying to accomplish........... All the clamp on meter will tell you is the amps currently going through the wire while something is in operation...... For instance, if one A/C unit is running, the meter may read 13A. If 2 A/C units are running, the meter may read 26A (plus whatever lights, TV etc are running)..... I don't see where this info is particularly useful to someone that wants to know if the campground service is adequate for his/her rig.Lou Schneider said:
On the other hand, if the user were to take a voltage reading (with any cheapo multimeter) and finds the CG voltage is only 102V, that would be a warning not to use the AC and put the fridge on propane instead of electric.......
It just isn't clear what the OP is trying to accomplish.
Quillback 424
Well-known member
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- Mar 10, 2011
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Buy a $30 digital meter that has a pop up overload protection device if possible. Use the voltage scale only until you get some tutoring on the current and Ohm scales. The voltage scale will have built in overload protection because of it's design... you ain't gonna cause any damage to the meter or your RV on the voltage scale.
Also, buy an extra set of meter leads with alligator clips that are substantial, pointed and open more then 1/4 inch.
Also, buy an extra set of meter leads with alligator clips that are substantial, pointed and open more then 1/4 inch.
Gary RV_Wizard
Site Team
I too am wondering what he wants to test? To verify proper function before plugging in, he only needs a voltmeter, and the $5 (or less) ones work just fine. I have 3-4 of them, in addition to a top quality meter, and the voltage readings are correct on all of them (except for modified sine inverter output).
There is almost nothing that an RVers needs to check that requires much precision or accuracy.
There is almost nothing that an RVers needs to check that requires much precision or accuracy.
carson
Well-known member
Good point Gary, How did we ever get along a few years ago with analog meters ? They even had an accuracy adjustment screw for accuracy . 1 decimal point was impossible to define. Nowadays we rely on 1, even 2, decimal points to determine accurate battery voltage readings.
Even mirror-scale meters depended on the quality of meter to show the true voltage.
How did we ever get along in those days ? Now we rely on $5.00 VOM's.
Just reminiscing....
Larry N.
Well-known member
FreddyS said:
I didn't say they were precision instruments, I just said that they are all you need for most RV uses. I've got two $4 VOMs from Harbor Freight and they're generally within half a volt DC and one volt AC when compared with my much better/more expensive unit. As to 30 amps, that's not something you do with any VOM -- what are you trying to measure? What will it tell you?
OP
OP
FreddyS
Well-known member
Thanks All. Was not exactly certain of what I needed. Now I am. I need a 30 amp tester (voltmeter) to test the shoreline outlet and an inexpensive multimeter to check things like outlets and fuses. 
Thinking of ordering this thru ebay. I already have the 30 to 15 plug reducer.
http://www.ebay.com/itm/Camco-55263-RV-Electical-120-Volt-In-Line-Voltage-Monitor-/130999991408?pt=Motors_RV_Trailer_Camper_Parts_Accessories&hash=item1e80353c70&vxp=mtr
Thinking of ordering this thru ebay. I already have the 30 to 15 plug reducer.
http://www.ebay.com/itm/Camco-55263-RV-Electical-120-Volt-In-Line-Voltage-Monitor-/130999991408?pt=Motors_RV_Trailer_Camper_Parts_Accessories&hash=item1e80353c70&vxp=mtr
Freddy....... pay attention ;D....... You don't need an "AMP TESTER" (whatever that is)...... All you need is an inexpensive multimeter......FreddyS said:Thanks All. Was not exactly certain of what I needed. Now I am. I need a 30 amp tester (voltmeter) to test the shoreline outlet and an inexpensive multimeter to check things like outlets and fuses.
You put the probes in the shoreline outlet to be sure that you are getting between 105- 125V....... If you are, you're good. If you aren't, flip the switch off & on and test again. If the reading is too low or too high, report it to the CG office and ask for a different site. If the entire CG is reading low (which is rare)...... just don't hook-up to shore power until it is fixed.
OP
OP
FreddyS
Well-known member
Wavery said:
K. Thanks for the help. I sure need it...... :-[
John From Detroit
Well-known member
I will second the Harbor Freight 5 buck special. (Have 2 of 'em)
Just bought a Crafstman 82369 Clamp On 400 amp AC/DC multimeter.
Does Frequency, Percent duty cycle, Temp. Current and voltage. I think it was 60 or 70 bucks, They also have a 100 dollar model and a couple of FLUKE (A top name in this kind of meters) that are UP from there.
Just bought a Crafstman 82369 Clamp On 400 amp AC/DC multimeter.
Does Frequency, Percent duty cycle, Temp. Current and voltage. I think it was 60 or 70 bucks, They also have a 100 dollar model and a couple of FLUKE (A top name in this kind of meters) that are UP from there.
Tourmaster
Well-known member
You might want to consider a Progressive Smart Surge Protector. http://www.progressiveindustries.net It will do all that work for you. Granted it is an expensive item but you generally don?t have to worry because it will shut you down if something is wrong. Just my two cents unless I am missing something here.
