I have decided to do some engine modification for the first time. I would like to know what kind of Meter I need for all purpose Model Railroading?
Recommendations on Meters at a reasonable price.
Thanks in advance
For most model railroad purposes, the cheap ones they often put on sale at Harbor Freight for $2.99 are plenty good enough. We're not doing high precision electronics here. At $2.99 it's almost cheaper to just buy a new one than repalce the batteries in one - sad but true. I have 3 or 4 of these scattered about, so I don;t have to hunt one down when I need it - one's in my car, another's in my model railroad toolbox, and another is in my desk drawer.
I've seen this very same meter sold for as much as $15 elsewhere. Don't be fooled.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I prefer analog meters with a nice, easy to read, big face. The analog meters have manual scale selection and a sometimes bouncing needle, which gives me a better feel for what is happening when I am taking measurements.
Ideal would be a 0-15 volt DC scale, but most multimeters I have seen have 0-10 and 0-25 volt scales. I use mine all the time to check out vehicle 12 volt systems, so good resolution in the 10-14 volt area is critical to determining how chargers and batteries are actually doing.
For model railroading work, the ability to read currents from 10ma (LEDs) to 30-80ma (small bulbs) to 100-300ma (can motors) to 0.3 amp - 2 amp (open frame motors) are the critical ranges. Measuring current is typically the weak point of most multimeters. Look carefully at the scales included and see if you can read the difference between 10 and 12ma, or 1.1 and 1.2 amps. Another words, you need to be able to detect a change of current of 10% (5% preferred) at both the low and high end of the likely currents.
Sears used to have a pretty nice selection of analog meters at reasonable prices - that's typically where I bought mine.
my thoughts, your choices
Fred W
Sounds good. One problem. I went to their site and can not find anything. What is the meter called?
Search for "Multimeter" and you will find what you need.
I have had three of those meters for some time. Make a mistake using the meter and the damage cost about $2.99. Throw away meters you might say. I keep a couple extra fuses for the amps scale protection.
Started out with a Heathkit analog VOM about 1957 and all I use now are the digital meters. Less loading of the circuit and more accurate readings than the analog type. Loading is probably not an issue for mrr use but I work on other type electronic circuits.
Analog meters can be damaged by incorrect use. The meter movement is the issue.
VTVM's have higher input impedance but were generally 120vac powered.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
So far all the moderate price multimeters seem to go up to 200ma not 300ma as you suggested. Other that the can motor would I need this reading for anything else?
There's really no need to be that accurate. For things like DCC decoders - they are usually rated to the nearest 1/4 amp or so, like the 750ma Micro-Tsunami, or others with 1 amp stall capacity, or 1.5 amp stall capacity with a 2 amp surge,etc. What you need to test for is that the stall current doesn;t exceed the decoder's limit, so if the meter has to switch to a high amp range to read over 200ma and you can only get to the nearest 100ma, you'll be fine. Measuring LED currents? What for? LEDs have a maximum current specified as part of their characteristics. Design the circuit to supply less than that and you are safe.
I keep saying that if I was designing more complex electronics I'd want a higher end meter (actually I do have one, but I rarely take advantage of the finer settings on it, at elast when workign with model railroad equipment), and as I try to think of a good example, I uusualyl can shoot it down by thinkign that if I just apply the appropriate formula, say for calculating the correct bias resistors for a transistor circuit, I don't really need a meter for that, it's all math. Verification? I guess I trust myself to look up the proper formula and apply it - like knowing that if I have a 12V DC power supply and a 1K resistor and a 3.1 volt LED, there will be about 10ma of current flowing through the LED, and if the LED is rated for 25ma there is no danger of it blowing up.
One place where analog meters DO have an advantage is when there are fast transients - when things change quickly. Digital meters tend to have a slower response time, so the numbers don't change so fast you can't read them. There could be a brief drop to 0 and back to normal and the numbers ont he digital meter won't even change - but the needle on an analog meter would. It may not be able to drop to 0 and go back up, but you would see it dip and go back and know SOMETHING happened.
hwolf So far all the moderate price multimeters seem to go up to 200ma not 300ma as you suggested. Other that the can motor would I need this reading for anything else?
The inexpensive digital meters have a 10 amp max scale.
The expensive digital meters have a 20 amp max scale.
You really have to read ALL the meter specs.
I have a Heathkit Model IM-28 Vacuum Tube Volt Meter (VTVM) but haven't used it for nearly 10 years now since Harbor Freight started selling their digital VOMs for $2.99, or sometimes on sale for $1.99.
For model railroad purposes, nothing fancier than the Harbor Freight meter should ever be necessary.
As Randy Rinker said, with the price of Harbor Freight meters being what it is, you can get several and keep them in different locations so you don't have to go hunting for one when you need it. I have four or five of them spread around at my house and the club.
All you weekend warriors with the long honey-do lists grab this handy multimeter and get started! This RadioShack 15-Range Digital Multimeter is a welcome addition to any do-it-yourselfer's tool kit. Plus, it'll come in handy for the hobbyist as well.
The Radio Shack one is a nice one. That would work fine. The HF one, they don;t list on their site, but it appears frequently in the sale flyers I get in the mail - also they often just have them. Sometimes $2.99 and sometimes $3.99.
The DC amps is the limitation. Can only measure to 200ma. Most model railroad HO scale motors draw over 200ma.
All the small meters like this I have seen have a 10 amp scale that is used for measuring motor current.
Yes, Harbor Freight sold out all their small digital meters. You can get them new on ebay for $10.00 or less.
hwolf These are the Specs for the Radio Shack $19.00 Multimeter. Does this take care of all my needs? When I looked at Harbor Freight I did not see one that you are describing...
That one does not have enough range on the current(200ma max) , but the $29.99 one would work:
29-Range Digital Multimeter
This one from Harbor Freight would work and is listed as in stock(on sale for $4.99):
7 Function Digital Multimeter With Backlight
richg1998 Yes, Harbor Freight sold out all their small digital meters. You can get them new on ebay for $10.00 or less. Rich
That's strange, I saw almost 100 of them on the shelf at a Harbor Freight in Tucson, Arizona, last week. They even had a large "bargain bin" filled with them.
Ok, my mistake. I searched the site for meter and they did not show up. I have used the word meter in the past and the cheap ones always showed up.
I just searched their site for multimeter and see a bunch of the cheap ones. I hope the OP sees the messages posted here about hose meters.
Harbor Freight changed their site recently. Sorry dudes & dudettes. I live a few miles from a Harbor Freight but try to avoid it. Always seem to be buying another tool.
I would just go to radio shack and get a decent analog meter.
Springfield PA
Does anyone still know how to read one properly? Or know why, for example, there is a strip of mirror finnish on the face?
Having gorwn up on analog meters, for casual use I would still recommend a digital. Unless you are specifically trying to track down transients that the digital meter doesn;t react fast enough for (and there are some devent (but not cheap) Flukes that have an analog bar graph along with the digital display and DO have a fast response time on the bargraph part). Actually, for a rank amateur I would suggest an autoranging digital meter, no need to 'guess' ahead of time where the parameter your are measuring will fall Most digitals aren;t damaged by going outside the selected range scale, other than overcurrent blowing the internal fuse, but over or under range conditions aren't always obvious, particularly on the low cost models
rrinker Does anyone still know how to read one properly? Or know why, for example, there is a strip of mirror finnish on the face? Having gorwn up on analog meters, for casual use I would still recommend a digital. Unless you are specifically trying to track down transients that the digital meter doesn;t react fast enough for (and there are some devent (but not cheap) Flukes that have an analog bar graph along with the digital display and DO have a fast response time on the bargraph part). Actually, for a rank amateur I would suggest an autoranging digital meter, no need to 'guess' ahead of time where the parameter your are measuring will fall Most digitals aren;t damaged by going outside the selected range scale, other than overcurrent blowing the internal fuse, but over or under range conditions aren't always obvious, particularly on the low cost models --Randy
Can't argue with your points, Randy, about casual use. Yes, I do know what the mirror strip is for. And I still personally prefer analog meters. My problem with auto-ranging and digital readouts is they can provide a false sense of accuracy that may or may not be there, or even wanted in a given situation.
For the same reasons, I despise digital speed readouts in cars. I found out when teaching my son to drive, and then more carefully observing my wife, the temptation and the visual reinforcement to drive the **** digital readout instead of looking outside. I had to create a cardboard cover for the dash to teach my son to drive outside, and that he could easily judge his speed (quite accurately) without ever looking at the speed readout. I've also seen the same issues doing labs in high school physics classes with digital readouts on the instruments. The students get a nice looking numerical result with no idea of what it means. Digital instruments actually take more teaching, not less, to help folks understand what they are looking at.
An analog guy in a digital world.
rrinker Does anyone still know how to read one properly? Or know why, for example, there is a strip of mirror finnish on the face?
IIRC -- you're supposed look at the face of the meter from as close to 90 deg as possible... the reflection of the needle will be dead under the needle when you're looking at it right.
-Dan
Builder of Bowser steam! Railimages Site
Are you ready for this. I just went to throw the Ad papers out from my mail box. Guess what I found. A Harbour Freight Tools flyer in espanol with an Ad for the 7 function meter @ $2.99.
My question is this. If the Radio Shack at 200ma might not be enough, what about this meter?
Is it the same as this one:
7 Function Digital Multimeter
If so, then yes. The specs on the website only list current up to 200ma, but in the picture and in the manual you can see that it has a 10 amp range.
Question. Isn't 200 ma the same as 2 Amps?
hwolf Question. Isn't 200 ma the same as 2 Amps?
200ma is 0.2 amps. Go to your local Radio Shack and look at the meter.
How to find a quick answer about this.
http://tinyurl.com/2ccjh9m
For model railroad use, the digital meter will be sufficient.
I have seen analog meters damaged by incorrect use by new users or dropped.. The movements can easily be affected and give you incorrect readings.
This is not rocket science.