DMM for automotive use - Page 1
Forum section: electronics / beginners

author: Autoelectrical
author_rank: Contributor
timestamp: October 21, 2012, 12:03:48 am
content: Hi,Forgive me as I am not an electrician, First and foremost I am looking for help choosing the right Digital Multimeter to use with automotive electronics.My local autoparts store carries an "Actron AutoTroubleShooter Digital Multimeter & Engine Analyzer" Model Model# CP7677. Looking at the reviews, it is a popular first buy at a $50+/- price point, and then after people have actually used it, it gets less than stellar reviews.Things I have done where a good multimeter is important (Things I would use it to check):Upgraded from single batteries to dual batteriesUpgraded 105amp alternator to a 300amp alternatorUpgraded alternator to batter, battery to chassis ground, battery to engine ground to 1/0aut 5200 strand tinned cablesTaken a cigarette lighter USB charger apart, wired 12 inch leads on it, ran a hot from the battery (fused) to inside the car and wired it, and then ran a ground inside the car and wired the USB Charger to leads. (need to make sure it is pulling 5v @ 2000mah (full load)I am also making some future changes where I need to make sure everything measures out correctly:I want to take either 4 or 8 of these:http://www.cree.com/led-components-and-modules/products/xlamp/discrete-directional/xlamp-xmland make a work light that is installed under the hood of my truck to work on the engine at night 4 LED's would be about 4000 lumens (about the light output of 2 x 23w CFL'S/100w incandescent light bulbs) with a light switch. But I need a DMM that will give me accurate readings for this application.I don't mind spending the money on a quality Fluke 87 or an Agilent 1253b (if for my use it will last me many years before needing replacement.) I need it to be readable outside or in a garage. What are some suggestions?

author: Rerouter
author_rank: Super Contributor
timestamp: October 21, 2012, 12:15:57 am
content: ok i'll skim away the excess of detail and point out what your looking at,firstly you didnt actually tell us how you plan to use one in these applications, be it voltage current, etc and the rangesso i'll go off assumptions"upgrade batteries" basic volt meter, or is there something else you need to check with one, (0-36V?)"105/300A Alternator" high current clamp meter or use of an external shunt, the clamp type cannot measure low DC currents, the shunt can (voltage drop across a known resistance)however on a practicality side, the clamp meter is just hook and test, the shunt is cut in series,"number 3" (not a bloody clue what you are talking about)"usb charger" generic multimeter should more than cover it,"leds" what about it needs to be accurate?from what i can scrape i would say, a high current dc clamp meter AND a generic sub $50 multimeter,

author: Autoelectrical
author_rank: Contributor
timestamp: October 21, 2012, 12:37:36 am
content: Quote from: Rerouter on October 21, 2012, 12:15:57 amThank you Rerouter, My fault.I upgraded the main wiring in my truck and want to be able to measure the volts and amps generated by my alternator and make sure that both batteries are charging correctly. ( I guess I would need the clamp meter for that).Then for working with USB and LED's in the vehicle, I need a way to accurately measure mah, forward voltage, reverse voltage and how many amps or the current that is being pulled by a number of LED's wired in series or parallel so I can chose the correct transformer or any other devices I need to put in line so I do now blow or under power the led's in the truck.

author: Lightages
author_rank: Unknown
timestamp: October 21, 2012, 12:47:13 am
content: I agree with Rerouter. A clampmeter that will do DC, and a good middle range multimeter. I can recommend the UNI-T UT61E as a good middle range multimeter that will be useful and safe for more than just automotive work. The recommended multimeters by Dave in his shootouts would also be good buys. As far as a clamp meter goes I have zero experience with the more recent models as mine is rather old now but functions perfectly well.

author: Rerouter
author_rank: Super Contributor
timestamp: October 21, 2012, 12:56:36 am
content: Quote from: Autoelectrical on October 21, 2012, 12:37:36 amfor currents higher than 10A, yes almost always in this case,Quote- mAh, as in milliamp hours? that is just current times length of time, 99% of multimeters have a mA range, you just have to be aware of burden voltage(multimeters measure the voltage drop across an internal resistance to work out current, thus it will throw off your voltage and current readings a little)- Forward voltage is a factor of current on diodes, so a diode check function will be different to in circuit testing,- Reverse voltage, why would you need to test that? on these it should be close to 40V or more, its when the diode breaks down and starts conducting the other way,- A, amps and current are the same thing, one is just the unit and one the term,

author: retiredcaps
author_rank: Super Contributor
timestamp: October 21, 2012, 03:45:43 am
content: Quote from: Autoelectrical on October 21, 2012, 12:03:48 amDon't forget to factor in usability features like- backlight to help you see the reading- magnetic hanger accessory so you can position the multimeter somewhere safe away from fan belts, hot radiators, etc- something like Fluke's touch hold feature which allows you to concentrate on making proper probe contact in tight or dangerous spots/areas. Once the multimeter gets a stable reading, it will beep and freeze the reading on the screen after you have removed the probes- min/max to record the lowest, highest and average reading- silicon probes with aligator clips. The silicon probes are less likely to tangle/break in cold/hot weather while the clips allows hands free readingsThis video may also help you consider some other features (NO - I'm not a Fluke Fanboy, but this video is useful for you).

author: samgab
author_rank: Frequent Contributor
timestamp: October 21, 2012, 04:10:45 am
content: Quote from: Autoelectrical on October 21, 2012, 12:03:48 amI suggest the Fluke 88V, rather than the 87V.The Fluke 88V is specifically for automotive use, but also has all the functions and features of the 87V, so you can also use it for electrical and electronics general use too.http://www.fluke.com/fluke/auen/digital-multimeters/fluke-88v.htm?PID=56148http://www.myflukestore.com/crm_uploads/fluke_88v_automotive_multimeter_datasheet.pdf

author: samgab
author_rank: Frequent Contributor
timestamp: October 21, 2012, 04:13:34 am
content: PS, I wish I'd gotten the 88V instead of the 87V, if only for the fact that current defaults to DC rather than AC!

author: Autoelectrical
author_rank: Contributor
timestamp: October 21, 2012, 06:14:38 am
content: Quote from: retiredcaps on October 21, 2012, 03:45:43 amThank you retiredcaps, that video was great and clarified allot for me.

author: Autoelectrical
author_rank: Contributor
timestamp: October 21, 2012, 06:18:16 am
content: Quote from: samgab on October 21, 2012, 04:10:45 amThank you samgab,So I would be looking at a Fluke 88v or in the video posted earlier, the fluke 239 (more overkill than what I would ever need, but the remote display is nice).What other options are there with high quality multmeters? Agilent, Grossen Metrawatt that are geared more towards Automotive use, but still work as a general purpose multimeter.

author: Autoelectrical
author_rank: Contributor
timestamp: October 21, 2012, 06:20:05 am
content: Quote from: Lightages on October 21, 2012, 12:47:13 amHi Lightages,Thank you, I checked that one out and for about $100 +/- that looks like a nice meter. I will take that one in to consideration since it is less expensive than a fluke :-)

author: T4P
author_rank: Super Contributor
timestamp: October 21, 2012, 06:22:31 am
content: Wait a sec ... 100W incandescents only produce at best 1000lumens not 4000lumens and 2x23W CFLs produce at most 2760 lumensAnd yeah, get a clamp meter to measure current, no point looking for a DMM which will do that, because none of them will!About silicon probes and such, there's no need to buy a fluke meter just to get probes, get a 50$ class meter and buy some agilent probes (much lower price!)I'll go as far to say the UT61E fits everything he wants. No need for a magnetic strap. And it's a 50$ meter if you have not been looking at shoddy sourcesOr the U1241B (Bluetooth support for your android device) So it's wireless of some sort

author: grenert
author_rank: Frequent Contributor
timestamp: October 21, 2012, 08:08:35 am
content: Quote from: samgab on October 21, 2012, 04:10:45 amIf true RMS is important to you, the 88V is not true RMS, unlike the 87V.

author: Autoelectrical
author_rank: Contributor
timestamp: October 21, 2012, 01:50:32 pm
content: Quote from: T4P on October 21, 2012, 06:22:31 amI guess lighting gets really confusing with all the different configurations you can have, I switched out all my incandescents for 26w CFL's. The 26w CFL's are "daylight" 5000k-6000k" and claim 2300-2500 lumens per bulb.I don't have the equipment to verify what they are claiming is true unfortunately. I assume that equipment is more expensive than what I would buy for personal use or as a hobbyist. I am checking out the UT61E and the U1241B that you mentioned now.Bluetooth where I could see everything on my Galaxy S III would be nice :-) All my ECU diagnostic tools for the car have modules that push data via bluetooth to my cell phone.Update:Wow, there is not much that can be said for android apps on a nice phone:The Agilent meter app for bluetooth:https://play.google.com/store/apps/details?id=com.agilent.mobilemeter&feature=search_result#?t=W251bGwsMSwyLDEsImNvbS5hZ2lsZW50Lm1vYmlsZW1ldGVyIl0.The Agilent logger app for bluetooth:https://play.google.com/store/apps/details?id=com.agilent.mobilemeterlogger&feature=search_result#?t=W251bGwsMSwyLDEsImNvbS5hZ2lsZW50Lm1vYmlsZW1ldGVybG9nZ2VyIl0.And Agilent is offering a kit with the meter, blue tooth adapter and a few other things for $205 so it is sort of in the middle of the range ( $50 (low) - $450 (High/Fluke 88v)

author: Autoelectrical
author_rank: Contributor
timestamp: October 21, 2012, 02:19:19 pm
content: Quote from: grenert on October 21, 2012, 08:08:35 amI would need to understand what True RMS is. The only time I have seen RMS raitings listed working on a vehicle, is with the car stereo amplifiers, they list an RMS Rating which is much lower than the power rating they claim in "watts per channel" for the amplifiers.Is RMS or True RMS more important for what I am looking to do? (I am not sure at this point). In the end I want an accurate multimeter that will last a long time whether it is $50 or $500 and as others have mentioned, back lighting, data logging to an adriod device, etc are extra perks that are nice convenience features, but may not be necessary.

author: Lightages
author_rank: Unknown
timestamp: October 21, 2012, 02:45:28 pm
content: What you have been doing with auto electrical does not require true RMS. Having said that, it is still desirable to get true RMS as sometime in the future it might be something you wish you had. As far as bluetooth and other "nice to have features" I really would recommend keeping things simple. Imagine trying to hold a phone, and another device with leads while trying to see what is going on with your head buried under the hood. A simple meter is a much better idea.When I recommended the UNI-T UT61E it was with an eye towards overall general usefulness in anything electric/electronic and from the price it can be had for. The idea is that will almost certainly wish for more than one multimeter in the future and this would be a good start for you to learn your real needs after experience with a multimeter. Once you have decided (or not) that the UT61E does not do what you want, then you can then buy the bigger buck meter but still have the UT61E as a decent secondary meter. The 61E has a data cable to log data on a computer if you wish to do some kind of logging of charge rates for batteries or something like that.I am not a UNI-T fan boy, rather I would recommend that you do not buy anything higher in their multimeter models than the UT61E. As far as a clamp meter goes, I can't believe I am saying this, it looks like the UT204 is a decent buy for what you want to do. There have been favorable comments from an owner or two on this forum about it. I have no experience with it but it does look worthwhile.My recommendations come from the fact that you are not 100% sure what you need or want to do with the meters. Therefore the meters I have mentioned are good value and will not break the bank while you learn more about the subject. I would not recommend an auto-specific multimeter for you at this time because your needs seem to be aimed more at electrical systems rather than motor control and fuel systems. The auto-specific ones tend to have mainly the added functions of Tach and Dwell, and lower specs in accuracy for the things you want to do.If price is no object, then it is hard to not recommend a Fluke 289, or 87V/88V, or Brymen BM867/869, or Amprobe 140/160, for a top of the line multimeter. The UEi DM397 also looks like a great meter but I have seen zero reviews or tear downs of this one.Again price no object for clamp meter, there are MANY, and I have no experience with anything recent.

author: T4P
author_rank: Super Contributor
timestamp: October 21, 2012, 05:05:25 pm
content: Right now the Agilent meters come with bluetooth free if you are buying from the authorized distributors like Farnell/Element14/Newark depending on where you liveBut always ask firstOh yeah, just as an info nugget there's no need to spend 200bucks on a clamp meter, Why would you need safety of a fluke on a clamp!The UT204A < Note the A , it's a great clamp meter on paper and reality, another product done well by UNI-T (I need to get myself one soon!)TrueRMS, 600amps DC and AC (DC+AC is another thing by itself) Temp! Oh great ... that's a nice add-on for slightly more than 40bucks! (I don't need temp on a clamp or DMM though as i have a dedicated K thermocouple meter... but it can come in handy)Where do you live BTW?Because DX has the UT61E & UT204A in their AU warehousehttp://dx.com/p/uni-t-ut204a-1-5-lcd-digital-clamp-multimeter-1-x-9v-6f22-127969?item=1http://dx.com/p/ut61e-2-6-lcd-digital-multimeter-red-black-1-x-9v-6f22-battery-113306?item=2And luckily it has the same probes as the UT61E which i can say is one of the best probes to come out of china though you need to clean them with some IPA (Other than the UT-L16 or some mastech probes as well as brandless probe i got for 4$)I'll say get these so further down the road if you do want a tachometer and dwell period (the UNI-T ones do 4cyl/6cyl/8cyl) a UT109 is available but i cannot vouch for their automotive DMM as i am not one myself but if you do have the money i'll say you might like a fluke/agilent instead.

author: samgab
author_rank: Frequent Contributor
timestamp: October 21, 2012, 10:24:22 pm
content: Quote from: grenert on October 21, 2012, 08:08:35 am(Edit: rephrasing) The 88V is RMS value calibrated (as opposed to "true RMS"). I wasn't sure, so I downloaded the manual, and under AC current, the note reads:"AC conversion is ac coupled and calibrated to the rms value of a sine wave input."and under AC Voltage:"AC conversionsare ac coupled and are average responding, rms indicating."To OP:Why RMS (Root Mean Square)?The purpose of RMS value is to simplify power calculations by providing equivalent DC voltage thatwould develop the same average power in resistive load.The RMS value equates to the same amount of heating that an equivalent DC Voltage and Current would result in.An RMS calibrated averaging meter like the 88V will give the same result as long as it is a pure sinusoidal waveform.As lightages says, you probably won't need true RMS for purely automotive uses.But I agree with his suggestion of the UT61E, for general electronics use as an entry level meter.But you mentioned the 87V in your OP, and stated that you wanted a meter specifically for automotive purposes, so the 88V seemed like an ideal choice.

author: Lightages
author_rank: Unknown
timestamp: October 21, 2012, 11:28:18 pm
content: Both meters I am recommending ARE True RMS btw.

author: Autoelectrical
author_rank: Contributor
timestamp: October 22, 2012, 01:06:53 pm
content: I want to thank everyone, This has given me some things to think about. I have some choices from $50 on the low end, to some high $$$ meters and information on clamp meter's. All I have to decide is what route I want to go with.At the moment I am leaning towards 2 meter's. A main one (more expensive) and a backup and then a clamp meter.

author: Autoelectrical
author_rank: Contributor
timestamp: November 02, 2012, 04:56:44 am
content: Hi Everyone,Well this has been an adventure. I wanted to thank everyone that educated me on the differences in meters because I started out knowing nothing about them.What I did not know is; I know so many people with backgrounds working in the electrical field and a friend of mine told me he had a few used multi meters and gave me one he did not need anymore. I know this is way overkill for what I need, but I ended up getting a Fluke 789.Now I need to figure out how to use it and which clamp to get for it to measure over 10 amps. Will the clamps suggested earlier work with this meter?

author: T4P
author_rank: Super Contributor
timestamp: November 03, 2012, 08:41:50 am
content: The clamps work independently.

author: Wytnucls
author_rank: Super Contributor
timestamp: December 20, 2012, 09:34:16 am
content: Quote from: Autoelectrical on November 02, 2012, 04:56:44 amThe 789 is a good true RMS meter and process meter, but its current shunt is limited to 1A (AC and DC). You need a compatible Fluke clamp (AC/DC) to measure higher amperage. The i410 is the one to get (rated to 400A).http://www.fluke.com/fluke/usen/accessories/Current-Clamps/i410.htm?PID=56301http://www.ebay.com/itm/Fluke-i410-AC-DC-Current-Clamp-/321043641982?pt=LH_DefaultDomain_0&hash=item4abfb1367e

author: G7PSK
author_rank: Super Contributor
timestamp: December 20, 2012, 05:53:28 pm
content: Get something along the lines of this Mastech clamp meter, I got one in order to measure alternator output current, it's good to 10 mili amps on both ac and dc and measures Hz on the clamp as well, I found a very useful feature is the led light on the clap so that you can see the wires in dark corners this comes on with the back light when set to the clamp ranges.http://www.ebay.co.uk/itm/271084217607?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

author: Achilles
author_rank: Regular Contributor
timestamp: December 20, 2012, 08:25:06 pm
content: well, I do use a current transducer like Wytnucls has shown as that also opens me the possibility to use it with the Oscilloscope....It doesn't need to be fancy new one, as you can sometimes grab older models on ebay. I paid 15Euro (plus 6Euro shipping) for mine. It's an ITT Metrix with 100 and 100A modes...served me quite well this far.....