What is the best way to check your voltmeter?Some years ago I ran into the problem where the meter read voltages too high when its battery was low. That took a while to discover since it happened gradually.Now I found my meter has been reading low for an unknown time. Kept seeing a difference of about 0.2 volts between Trimetric and other meters but thought it was those other meters that were reading high for some reason like voltage drop that confuses things. Anyway, I finally decided that there was something wrong with the multimeter.Battery ok, fuse ok, leads ok confirmed by swapping them. No change.Got a new meter and the manual says to first check its voltage to make sure it is working right. Ha! Check it against what? It is reading about the same as the Trimetric and the other meters, so they seem to have voted on it, and sort of agree on the actual voltage within a 0.1 range.ISTR on here there was a way to confirm your meter's voltage using flashlight batteries or whatever it was. However, I also remember those eBay meters that are only accurate at higher voltages and are wonky at low voltages.So what can an RVer do "trying this at home" without having a calibration lab?

I guess I'd try a AA cell or maybe the wall socket.

Two obvious options, buy a good meter (like Fluke) or buy a cheap voltage standard. Here's a link about cheap voltage standards.

You need a sufficiently well calibrated/trusted voltage source.A normal AA cell is not that precise. Wall voltage varies as well, within limits. Perhaps the best simple method for a quick check is to find someone who has a good, trusted meter and compare readings--preferably someone with one that has been calibrated and certified by a proper calibration lab, if absolute accuracy is required.If you want to build a calibrator yourself, you might start with a precision voltage reference chip. Something like this TI LM4040 variant looks promising; that, plus a current limiting resistor plus a voltage source > 10V would give a 10V reference that's within 0.1% or so under any reasonable operating condition, quite sufficient to calibrate or check inexpensive and not overly precise multimeters. This is not at all NIST-level precision.There are many precision voltage reference devices available at varying costs, outputs, degrees of precision, etc.For many jobs, absolute accuracy is not essential; the actual values of 12.3V or 12.4V might not matter as much as the fact that there's a 0.1V change between them. For other jobs, of course, the actual true value of a reading may be rather critical.

Keep an eye out for a truck with ladders that are secured with romex. Ask the dude if he has a fancy meter and compare your reading to his? The battery idea seems good too. Stack several in series to see how accurate in the 12-14v range? (assuming you are most concerned about accuracy in that range)Or keep an eye out for kids/adults flying drones or RC planes. They usually have several voltage testers that measure even down to the thousandths and come pre calibrated.

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dieseltruckdriv
Explorer II
Feb 09, 2020
Thermoguy wrote:
I knew that when I posted it. Just a good meter for around $100. But, there are others, I have a $400 meter so I'm not going to spend the time to find a link to a cost effective good brand meter that measures DC current. By all means, if you have one, please post for others.
I was just letting people know as well.

This meter doesn't look too bad, but I have no experience with it.
Thermoguy
Explorer II
Feb 09, 2020
I knew that when I posted it. Just a good meter for around $100. But, there are others, I have a $400 meter so I'm not going to spend the time to find a link to a cost effective good brand meter that measures DC current. By all means, if you have one, please post for others.
dieseltruckdriv
Explorer II
Feb 08, 2020
Thermoguy wrote:
All meters, thermometers, etc have an accuracy rating. A good meter is +/- 1% or +/-2% of the reading. If you take 2 meters and read the same thing and both are accurate to +/- 2% you can now be off by as much as 4%, so best to not compare 2 meters. The best reading is one that is consistent, meaning if I am reading something and come back tomorrow to read the same measurement, it is within that accuracy rating.

Another point is that all of these meters, Fluke, anyone, are made in China. Better companies use the better manufacturers over there and have better QC. So, it makes sense to buy a better meter if you want better accuracy. A $25 meter is going to give you what you paid for, a cheap meter reading. You should buy a better meter. You can get a descent quality meter for less money than you think. Just search around for it. Stick with a company that makes meters and measuring devices and not some brand that has there label put on a Chinese POS.

This is a great Fluke meter used by lots of electricians at only $100...

https://www.amazon.com/Fluke-Electrical-Voltage-Continuity-Current/dp/B0006Z3GZU/ref=sr_1_5?keywords=fluke+multimeter&qid=1581182098&sr=8-5

There are other good manufacturers of meters that are comparable and probably a little less expensive.

The meter you linked to would be ok to test a pedestal, but not good for dc. We got them at work and I told them I don't even want one. I put it on 12 power supply, and it only gave the reading in volts. As in 11. I like to see hundredths of a volt at work. I do controls stuff, and when I am measuring 4-20 milliamps, it matters. That meter only does AC when measuring amps. I am not saying it is a bad choice, just be aware it is just very limited on DC stuff.
Tom_M1
Explorer
Feb 08, 2020
Thermoguy wrote:
This is a great Fluke meter used by lots of electricians at only $100...

https://www.amazon.com/Fluke-Electrical-Voltage-Continuity-Current/dp/B0006Z3GZU/ref=sr_1_5?keywords=fluke+multimeter&qid=1581182098&sr=8-5
This meter does not measure DC current. A better choice for RV use would be one that also measures DC current.
BrianinMichigan
Explorer
Feb 08, 2020
.2 volts and .01 volts. unless your adjusting a bias circuit, you should be happy with that. Back in the day the RCA Senior Volt ohmist was the standard. now my Fluke and my old B&K are the ones to go to. But testing the home A/C voltage they are off from each other by 2 volts. Good enought!
Thermoguy
Explorer II
Feb 08, 2020
All meters, thermometers, etc have an accuracy rating. A good meter is +/- 1% or +/-2% of the reading. If you take 2 meters and read the same thing and both are accurate to +/- 2% you can now be off by as much as 4%, so best to not compare 2 meters. The best reading is one that is consistent, meaning if I am reading something and come back tomorrow to read the same measurement, it is within that accuracy rating.

Another point is that all of these meters, Fluke, anyone, are made in China. Better companies use the better manufacturers over there and have better QC. So, it makes sense to buy a better meter if you want better accuracy. A $25 meter is going to give you what you paid for, a cheap meter reading. You should buy a better meter. You can get a descent quality meter for less money than you think. Just search around for it. Stick with a company that makes meters and measuring devices and not some brand that has there label put on a Chinese POS.

This is a great Fluke meter used by lots of electricians at only $100...

https://www.amazon.com/Fluke-Electrical-Voltage-Continuity-Current/dp/B0006Z3GZU/ref=sr_1_5?keywords=fluke+multimeter&qid=1581182098&sr=8-5

There are other good manufacturers of meters that are comparable and probably a little less expensive.
wa8yxm
Explorer III
Feb 07, 2020
theoldwizard1 wrote:
wa8yxm wrote:
In days of old when folks were bold I had a VTVM ...

You must be close to MY age !

Simpson 260, Tek 555 (half hour warm up time and a great and warmer), ...

Though I'm not on the Internet I'm 70.. (I never give my true age for security reasons but.. Well. close)
Gjac
Explorer III
Feb 07, 2020
theoldwizard1 wrote:
Gjac wrote:
If you have a HF mulimeter there is a pot inside that will adjust the voltage readings. I use my B&D charger and adjust the voltage reading on my HF meter to match it. I have about 4 meters that I use in the RV,house and car now that all read the same now.

Good start, but there is no guarantee that they will stay in sync across the whole range.

If you work in an electronics lab, there are two classifications of equipment; "estimate only" and "calibrated", typically once a year.
Your right, I tested mine at a lower voltage and it was off .01 volts, so I calibrate mine for my battery voltage 12 + volts. To send my meters out for calibration would cost more than my meters are worth, so to monitor battery voltage it is good enough. If I worked as an electronic technician and needed an accurate meter everyday for my job I would buy a Fluke.
theoldwizard1
Explorer II
Feb 07, 2020
Gjac wrote:
If you have a HF mulimeter there is a pot inside that will adjust the voltage readings. I use my B&D charger and adjust the voltage reading on my HF meter to match it. I have about 4 meters that I use in the RV,house and car now that all read the same now.

Good start, but there is no guarantee that they will stay in sync across the whole range.

If you work in an electronics lab, there are two classifications of equipment; "estimate only" and "calibrated", typically once a year.
theoldwizard1
Explorer II
Feb 07, 2020
wa8yxm wrote:
In days of old when folks were bold I had a VTVM ...

You must be close to MY age !

Simpson 260, Tek 555 (half hour warm up time and a great and warmer), ...

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