Multimeter Accuracy for Automotive - Calculating Ranges - Page 1
Forum section: electronics / testgear

author: ZappedMySelf
author_rank: Newbie
timestamp: May 28, 2020, 08:04:01 am
content: If you use your multimeter for your car comment below what you use and why.Many too expensive >$100 and i'd be lying if I will be using it enough to justify something that cost more than $50-$60 unless someone has a really good convincing argument. I'm not a electrician and my route through college was on the biology side so Ill never deal with anything other than what could be found in a house (120v 60amps?). I'm currently just dizzy with the large amount of multimeters available.I've probably spent hours over several days watching a huge range of multimeter reviews on youtube.Currently I'm looking for something that's accurate to .1ma in the 1-10 or mA range.Lets take the Aneng AN870 for examplehttps://www.aliexpress.com/item/33004463675.html.Specs on DC Current 1.9999A /19.999A / 19.999mA /199.99mA /99.99μA /1999.9μA ±(0.5%+3).So the math: 19.999 * 0.005 + 0.003 = 0.103ma plus/minus on a 19.999ma Measurement correct? That seems accurate enough for me.The Aneng V8 has a similar accuracy on 8mA plus/minus 0.099ma.The UNI-T UT191T also looks good. Only wish was that it used AA/aaa batteries so i could use my rechargeable batts. This unit seems to have the easiest fuses to source/find too.Really the only other feature I require is easily buyable replacement fuses.I read too many reviews of amateurs blowing them, im in the same group. And more likely so since most of us aren't electrical savvy.Any thoughts on your choice of multimeter for a car would be appreciated.

author: Marck
author_rank: Regular Contributor
timestamp: May 28, 2020, 09:12:43 am
content: If you are just doing basic automotive type stuff I would look at the UniT 210e. Dc clamp meter so you remove the risk of blowing fuses measuring current. Seems to have a reasonable reputation. It’s cheep for what it is I think seeing something similar with a fluke name tag is 5x the price.M

author: totalnoob
author_rank: Regular Contributor
timestamp: May 28, 2020, 11:25:11 am
content: Before you buy an Aneng, check the reviews on that model. I have the AN8009 and the resistance reading isssssllloooooowwwww, I should have paid more attention to those reviews, although I think the AN8008/8009 is just about the right size for most use in and around a car, but can't recommend them (there are only minor differences between the 8008 and 8009 models) based on how slow they are for measuring resistance. I did look at the AN870 but I remember not liking something about it (from either a review or the specs) but I can't remember what. You probably cannot go wrong with the old standby that everyone swore by a few years ago, the Uni-T UT61E. The only downside is that it has no backlight which you may need depending on where you are in the car when testing.I do agree with Marck's suggestion on also having a good clamp meter for testing amperage without having to break a circuit to do so. The UT210e gets very high marks from most people.

author: ZappedMySelf
author_rank: Newbie
timestamp: May 28, 2020, 05:05:00 pm
content: I saw some youtube reviews that it is just the leads on the AN8009/8008 that is bad. Changing it with some probemasters, etc, will result in super fast continuity testing speeds which I assume is the slow ohm readings you are talking about?UniT 210e is a really good choice as a secondary unit. It doesn't seem to offer amps measurement from the probes? Below is two videos on how i plan to use it on a car.One way is to measure amps draw from the whole car, just disconnect the battery.Another way is to measure mA draw from across your fuses.UNI-T UT61E, I might have to jump on that if i decide to go with a unit that uses 9v instead of just AA/aaa.I'm off to work a 10hr shift.

author: NoisyBoy
author_rank: Frequent Contributor
timestamp: May 28, 2020, 05:07:23 pm
content: I agree with others, but you won't be getting 0.1mA accuracy from clamp meters.0.1mA accuracy is not atypical for lab use, but you would rarely need it for automotive unless you are designing something. Measuring any parasitic draw is often much higher than that.If you are dealing with AC main voltage and you are worrying about frequent fuse replacement due to mistakes, buy something decent with ample protections, it is more than just easily replaceable fuses. Unfortunately, I don't know if anything is well protected at that price bracket. When you work with main, you really need to know what you are doing, always double and triple check your meter setting and plug placement before putting the probes on anything.Be safe.

author: ZappedMySelf
author_rank: Newbie
timestamp: May 28, 2020, 05:26:54 pm
content: You are right! I confused myself and forgot that the second method to measuring parasitic current draw was actually measuring mV not mA! They then use a chart to convert the mV to mA. Ive been looking for a meter that measures to 0.1 mA accuracy all this time for no reason! The clamp style UNI-T seems like it has everything i would need at this point.

author: Gregg
author_rank: Super Contributor
timestamp: May 28, 2020, 11:30:33 pm
content: Additionally you might add a couple of test lamps top your automotive test kit. The ones with the lamp in a screwdriver type handle and long ice pick type probe; one with an incandescent lamp and one with a low current LED for data and signal circuits that may not tolerate a low impedance path to ground. These are cheap and fast diagnostic tools. A little heat shrink along the probe is a good idea. Many times a corroded connection will show good voltage at no load, but won’t pass enough current to be operational. In addition, you might want to make a higher current test lamp out of an old halogen headlamp that will need 4 to 5 amps to light to test things like fuel pump circuits.Youtuber South Main Auto has lots of good automotive electrical diagnosis tips and is quite entertaininghttps://www.youtube.com/channel/UCtAGzm9e_liY7ko1PBhzTHA/videos