multimeter question
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richfinn
Well-known member
A good tool for auto electrics but they do wear out after about 3 or 4 years of heavy use, a Fluke will last a lifetime
Im currently on my 3rd power probe (my first pp3) as I cant live without one
MrMark
Well-known member
I wonder if anyone knows how the powerprobe iii "tests" for ground.
In its test mode it measures voltage between the probed point and B- to see if the test point is powered B+, but if instead of 12V it sees 0V, it has a decision to make. It could be an open circuit or it could be connected to B-, so I wonder if it then has logic to switch to continuity test with B- to see if that test point is a potential ground. I say potential because the continuity check would not be completely determinative. It would then light the green light. I wonder if there is a slight delay before it lights the green light when B- or so-called ground is determined to be continuous with the contact point.
Does anyone know how it works?
In its test mode it measures voltage between the probed point and B- to see if the test point is powered B+, but if instead of 12V it sees 0V, it has a decision to make. It could be an open circuit or it could be connected to B-, so I wonder if it then has logic to switch to continuity test with B- to see if that test point is a potential ground. I say potential because the continuity check would not be completely determinative. It would then light the green light. I wonder if there is a slight delay before it lights the green light when B- or so-called ground is determined to be continuous with the contact point.
Does anyone know how it works?
RBailey
Well-known member
A good tool for auto electrics but they do wear out after about 3 or 4 years of heavy use, a Fluke will last a lifetime
Im currently on my 3rd power probe (my first pp3) as I cant live without one
Switches wear, but they now come with user replaceable switches.
diesel research
Well-known member
April 30th.
Looks like the standard CJ4 may actually have some type of bluetooth/wifi as well. With the CJ4 I know the full blown deal is $1k, but seem to recall w/o all that manufacturer stuff, they had one for around $450. Maybe no more.
____________________________
While someone already posted a youtube vid (I didn't check it but HOPE it was the awesome TTI livingston toyota vid) let's recap.
Resistance test is not for wires. There are some exceptions but for the most part, relatively useless compared to better tests.
What is it good for? Inductive windings and resistors mostly. Unplugged and unpowered of course. Solenoids, coils, motor windings, injectors, speakers, other things using very fine copper wound hundreds or thousands of feet.
Switches and other contacts seem like another good place (because of the beep) but even then volt drop across contacts is better, since the contacts resistance often changes under real world loads. That's how circuit breakers work. Load it, heats up, breaks contact.
Your run of the mill wiring like normal 22-12ga wiring, continuity isn't really valid these days. Definitely not as the cables get larger. "ohm out" a sewing needle and you will see what I am saying. Would you trust that sewing needle to handle the load of a blower motor?
What if I need to do a volt drop test on a signal wire or pwm wire w/o a constant supply running across it? Well it gets a little tougher to load test those wires. Needs to be disconnected at both ends. Jumper wire power to one end, jumper other end to pin 86 of a typical relay. Ground pin 85 and you just created a load. Now you can measure across the wire for differential readings.
Had to check an injector (-) wire in such manner by unplugging injector AND pcm connector. (don't want to inject power into a pcm and smoke it, plus many are too hard to back probe these days.
Another trick to making the switches last, turn it on before making contact with the tip. The tip will take the little arc instead of the switch contacts.
Just as an example of what you are talking about for those guys who don't deal with this stuff on a daily basis:
Say you have a starter that is slow cranking. It uses a cable that carries 200A, and one of the terminals has .03 Ω resistance in it due to corrosion. A standard multimeter (even a good fluke like an 88V) is only good to .1 Ω, so it won't catch that doing an ohm test. Doing the math, 200A x .03 Ω = 6V of drop through the cable, which is easily detectable by any meter out there provided you are checking volts and not ohms.
theoldwizard1
Well-known member
Amazing how few people understand Ohm's Law !
If you really have to ACCURATELY measure things less than 1 ohm, you will need an impedance/inductance meter. These are typically bench top and you don't want to know how much they cost.
nate379
Banned
Yeah... My Dad had one of those and it seemed to be reading funky.
I set it on AC voltage, stuck the leads into an outlet. It went up in smoke with a big fireball
I set it on AC voltage, stuck the leads into an outlet. It went up in smoke with a big fireball
Fluke is indeed the Snap-on of multimeters. I had a basic Blue Point for a few years and was generally quite unhappy with it, average quality at best. The most annoying thing was the continuity test, buzzer stopped working and on a close inspection it turned out the little speaker/resonator broke off inside.
I spent about a week looking at the different models and decided on a Fluke 115, for the following reasons:
1. Reasonably priced when new, particularly if you can get it on ebay, with 3 years no questions asked warranty.
2. Out of the 110 series, it's the most complete as it has pretty much everything you might want from a multimeter except for micro amps and micro volts. What's the difference? Take a small gadget with a backlit display for instance. If you want to measure how much current the backlight is drawing, that would be milliamps. If you want to know what current, if at all, is drawn when device is not powered on, that would be microamps.
If I wanted micro amps, I would have to shell out for Fluke 87 which is significantly more expensive and I can't justify the extra cost.
3. The amps range can SAFELY go up to 20A which is quite a lot.
4. It has a latch on buzzer, the continuity beep is practically instantaneous. Almost all under 100 USD multimeters react with a small half a second delay and it can get annoying when you're under the dash in a awkward position and you have to double and triple check you've made good contact before you can say there's no beep.
5. Nice and solid feel. I'm expecting it to last way beyond your average meter.
6. Accuracy. This is a meter you can trust. This one doesn't score as high as the other advantages on the list as most of the time I don't need pinpoint accuracy, but it's nice to know nonetheless.
7. Last but not least, do NOT underestimate the level of protection that is not there with a cheap meter. Multimeters can quite literally blow up in your hand if you're using it on higher voltages and something goes wrong. That includes 220/110V mains.
That is not to say a cheaper meter won't do the job. My point is there are obvious differences between them, just as there's a difference between a Craftsman ratchet and a Snap on one.
I spent about a week looking at the different models and decided on a Fluke 115, for the following reasons:
1. Reasonably priced when new, particularly if you can get it on ebay, with 3 years no questions asked warranty.
2. Out of the 110 series, it's the most complete as it has pretty much everything you might want from a multimeter except for micro amps and micro volts. What's the difference? Take a small gadget with a backlit display for instance. If you want to measure how much current the backlight is drawing, that would be milliamps. If you want to know what current, if at all, is drawn when device is not powered on, that would be microamps.
If I wanted micro amps, I would have to shell out for Fluke 87 which is significantly more expensive and I can't justify the extra cost.
3. The amps range can SAFELY go up to 20A which is quite a lot.
4. It has a latch on buzzer, the continuity beep is practically instantaneous. Almost all under 100 USD multimeters react with a small half a second delay and it can get annoying when you're under the dash in a awkward position and you have to double and triple check you've made good contact before you can say there's no beep.
5. Nice and solid feel. I'm expecting it to last way beyond your average meter.
6. Accuracy. This is a meter you can trust. This one doesn't score as high as the other advantages on the list as most of the time I don't need pinpoint accuracy, but it's nice to know nonetheless.
7. Last but not least, do NOT underestimate the level of protection that is not there with a cheap meter. Multimeters can quite literally blow up in your hand if you're using it on higher voltages and something goes wrong. That includes 220/110V mains.
That is not to say a cheaper meter won't do the job. My point is there are obvious differences between them, just as there's a difference between a Craftsman ratchet and a Snap on one.
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richfinn
Well-known member
I used mine constantly, and after having to resolder the boards and swap out the cable and patch up the case with jb weld it got to the point where it was just easier to buy the new upgraded model. Saying that Im not complaining I just see them as a £100 consumable every few years, they are good value and very well made, I just use them in a tough environment. I do energize before powering up a circuit BTW
A fluke 87, will run around $350. But I also like the model that looks like a wiggy but you can read amps, $100.
The companies I work for buy fluke. I use my meter daily, and it gets used alot. I have had two break over the years. Few years ago, the knob broke off. Before that I dropped one and the screen cracked. I have dropped many since then, and no problem.
I wish you could turn the auto ranging off on the new ones, and have it stay off.
The companies I work for buy fluke. I use my meter daily, and it gets used alot. I have had two break over the years. Few years ago, the knob broke off. Before that I dropped one and the screen cracked. I have dropped many since then, and no problem.
I wish you could turn the auto ranging off on the new ones, and have it stay off.
Capt Chrysler
Well-known member
I have been on the Fluke wagon from 1990. Still my go to meter.
Capt. Chrysler
Capt. Chrysler
A good tool for auto electrics but they do wear out after about 3 or 4 years of heavy use, a Fluke will last a lifetime
Im currently on my 3rd power probe (my first pp3) as I cant live without one
If you wear out a PP3, pretty good chance its made its cost back about 10x., plus bottom line if somebody knows of a better tool I would love to hear about it.
I don't see it as a 100% go to tool, I have a $30 pen/probe DMM for all the non power stuff as well as a couple cheap $5 light in the handle ice pick type things.
*** Detecting ground ... Only way I can think of is to allow some small amount of current to flow. The trick in computer stuff is to keep the current so small it doesn't exceed load supported by the chips in the car computer, ideally so low it doesn't even make a noticeable load.
I think you may be overthinking how it works. Ever use a "smart testlight"? The ones with a red and green LED, and two alligator clips on the end? If you have B+ at the probe, they light the red light. If you have B- at the probe, they light the green light. You don't need a whole lot of logic to switch the two, because you have both paths to potential (B+ or B-) through the alligator clips. The powerprobe is the same idea.
They do have a continuity check, but it works a bit differently. You need to use the pigtail on the powerprobe, which acts as a ground. I imagine it does a voltage drop over the component being tested. If there is no continuity, the display does nothing. If it has continuity, but it's between 20kΩ and 2kΩ the display will show 0.0 to indicate a continuous path (like through a solenoid or coil). If the component has less than 2kΩ resistance, the display shows 0.0 and the green LED lights up. In all cases, there is no significant delay in determining what to display.
MrMark
Well-known member
I've never used a smart testlight, didn't know there was such a thing. Googling those terms brings up this interesting Innova or Equus Smart Testlight, that upon examination has some form of circuit board in it.
There are only three ways I know of to test for continuity to B- at a probed point (i.e., "ground" even though it is not grounded):
1) Apply a Voltmeter or test light between B+ and the probed point. It will show 12V or light if B- is there;
2) Perform a continuity test (sends a small current into the circuit and measures resistance) between the Probed point and B-, which is what I suspect the Power Probe does, even though it has an additional continuity test with the pigtail which is internally connected to B-; or
3) Create a dead short by connecting B+ to the probed point and seeing if the fuse or circuit breaker blows.
Think about what you would do with a DMM to perform the tests you are doing with the power probe III. You would first set to voltage and check between each terminal point and a known good ground (i would also check across the two terminals). You may find one is B+ or 12v. The other may not show anything. What is it ???
You would then switch to continuity to test for ground or you would remain on voltage but you would need to move your DMM probe off the known good ground and go to B+.
The Power Probe and the smart test light must do something logically to duplicate that test procedure as far as I can see. It has this switching capability because it is hooked up to BOTH B+ and B-, unlike a multimeter would be.
That Powerprobe scares me to death. I wouldn't let anyone use one on my car. Too dangerous in the wrong hands. I wouldn't even use it. There is too much oportunity for learning and discovery using the multimeter and it is safe.
There are only three ways I know of to test for continuity to B- at a probed point (i.e., "ground" even though it is not grounded):
1) Apply a Voltmeter or test light between B+ and the probed point. It will show 12V or light if B- is there;
2) Perform a continuity test (sends a small current into the circuit and measures resistance) between the Probed point and B-, which is what I suspect the Power Probe does, even though it has an additional continuity test with the pigtail which is internally connected to B-; or
3) Create a dead short by connecting B+ to the probed point and seeing if the fuse or circuit breaker blows.
Think about what you would do with a DMM to perform the tests you are doing with the power probe III. You would first set to voltage and check between each terminal point and a known good ground (i would also check across the two terminals). You may find one is B+ or 12v. The other may not show anything. What is it ???
You would then switch to continuity to test for ground or you would remain on voltage but you would need to move your DMM probe off the known good ground and go to B+.
The Power Probe and the smart test light must do something logically to duplicate that test procedure as far as I can see. It has this switching capability because it is hooked up to BOTH B+ and B-, unlike a multimeter would be.
That Powerprobe scares me to death. I wouldn't let anyone use one on my car. Too dangerous in the wrong hands. I wouldn't even use it. There is too much oportunity for learning and discovery using the multimeter and it is safe.
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Know how to read a schematic? Maybe this will help you understand how a logic probe works. A power probe is just a gussied up logic probe at it's core, but it has the additional ability to provide power/ground at the probe, and a volt meter built in. Really, there isn't much to them.
Key words there are "in the wrong hands". Using one as a test light or meter is perfectly safe, just don't go applying voltage or ground to random wires without understanding the consequences that doing so will have. No need to write off a perfectly serviceable tool just because it might be dangerous. If you did that to every potentially dangerous tool, you'd never get anything done.
MrMark
Well-known member
I'll read that Stick, it looks cool. Logic probe is a little different though. Logic probe has to make a call on high or low signal levels; the powerprobe may have logic probe logic but it seems to do more. It makes a call on high or low signal level (12v or 0v) but it has to take the additional step of determining whether the 0v reading is an open circuit or a "ground". So, I think the logic would go something like this:
If 12V is detected, light red light
If 0-2V is detected (just an example) test for continuity with B-, if yes light green light, if not no light.
Here's the smart test light
http://www.amazon.com/dp/B000KIGL6E/?tag=atomicindus08-20
If 12V is detected, light red light
If 0-2V is detected (just an example) test for continuity with B-, if yes light green light, if not no light.
Here's the smart test light
http://www.amazon.com/dp/B000KIGL6E/?tag=atomicindus08-20
Again, you are overthinking things. The logic isn't 0-12V, it's -12V to +12V to light up the LED's with the probe biased at 0V. The continuity test is separate from the "logic probe" part of the tool, and uses the pigtail as ground.
ddawg16
Well-known member
I have 4 meters...
Fluke 179
HP DMM
Cheap Sears DMM
and a Simpson 260
For acuracy and reliability....the Fluke.....and it does diodes......and man, do I love the magnetic holding strap.
The HP just stays in the garage....easy to use...auto shut off, so I have shown my boys how to test batteries.....they actually get a kick out of it.
The sears.....it's going flaky on me....might be time to drop it from the top of the garage...
And I'll never get rid of the Simpson 260....sometimes have a needle movement is hard to beat.
On a side note....I'm keeping an eye on CL for an old Amprobe....the analog type. It's too hard to set up SCR's with the digital type.....you need the analog type so you can see the needle bounce.
Fluke 179
HP DMM
Cheap Sears DMM
and a Simpson 260
For acuracy and reliability....the Fluke.....and it does diodes......and man, do I love the magnetic holding strap.
The HP just stays in the garage....easy to use...auto shut off, so I have shown my boys how to test batteries.....they actually get a kick out of it.
The sears.....it's going flaky on me....might be time to drop it from the top of the garage...
And I'll never get rid of the Simpson 260....sometimes have a needle movement is hard to beat.
On a side note....I'm keeping an eye on CL for an old Amprobe....the analog type. It's too hard to set up SCR's with the digital type.....you need the analog type so you can see the needle bounce.
Old fart. You had me with the Fluke 179, and I understand the HP and cheap Sears meters, but Simpson and Amprobe? Time to get with modern times and upgrade to a graphing meter or scope...
ddawg16
Well-known member
Old fart. You had me with the Fluke 179, and I understand the HP and cheap Sears meters, but Simpson and Amprobe? Time to get with modern times and upgrade to a graphing meter or scope...
Oh.....I have a scope....old HP single channel......and access to a Fluke scope meter.....
But my old Simpson does not need batteries.....something to be said for that.
sorry but at $300.00 people are not giving them away.
diesel research
Well-known member
(meanwhile, "mechanic" is so proud he can use his old fashioned skill and diagnose the starter, while saving time by avoiding wasting time on useless tests. Car now starts fine. Too bad it was really the loose/dirty connection that did the trick.
)les_garten
Banned
I had a friend of mine wanted to get a meter and start learning it. I told him to watch Ebay and get a 87. Took him about a week and he had a nice one for around $100.
If you look at completed listings, just recently quite a few sold in the $100-130 range
Don't make me do your searches for ya again...
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I miss using the Simpson 260's. This thread caused me to research if they are still available... they are. Unfortunately a low-end Fluke can be purchased for less than a new Simpson 260.
csargents1546
Well-known member
I love my fluke 89 IV, bought it about 12 years ago, used it while I went to school. The only thing that has gone wrong was not the meters fault, apprentice tech set it down and then the lift came down on it. Only broke the terminal block where the comm lead plugs in. I love how fast it is in reading volts, ohms. Accidently hooked it up to measure current, but the leads where still in the volts jack. Did not blow a fuse. Very impressed with that one.
MrMark
Well-known member
I looked at the logic probe circuit and you must be right. Unlike the multimeter, the probe has connections to both B+ and B- and the circuit takes advantage of that fact to use another method in lieu of the normal metered continuity step. Ignoring divided voltages less than source voltages, the probe tip may touch either B+ potential or B- potential or nothing (open circuit). The logic probe comparator circuit provides two current paths because of those two connections at the bat.: either B- at the bat. to B+ at the tip, or B- at the bat. to B+ at the tip. These two paths allow either the red or green to be turned on indicating continuity to either B+ or B- at the bat. as the case may be. The selection of reference voltages for the circuit is important.
richfinn
Well-known member
I can confirm that a broken or OC ground strap between the engine and battery will cause the probe to see "voltage drop" when you probe the transmission casing or engine castings but it also believes them to be "hot" by lighting up the red LED.
MrMark
Well-known member
Hot because they are hot (in the sense of B+ being present) if the downstream continuity to B- is broken and those parts are in the "grounding" path. There shouldn't be much working if that strap is broken. The B+ potential is present all the way back to the opening in the ground path because no current is flowing in the circuit; it's an open circuit.
how does the probe see "voltage drop." The probe does have a method of checking the resistance level of the ground path so it combines some elements of a voltmeter with the logic probe. It shows blank screen if high (over 20K? ohms resistance) and )0.0 if under 20K? and lights the green light with the 0.0 display if the resistance is under 2K, which is what its designers decided was a good ground.
how does the probe see "voltage drop." The probe does have a method of checking the resistance level of the ground path so it combines some elements of a voltmeter with the logic probe. It shows blank screen if high (over 20K? ohms resistance) and )0.0 if under 20K? and lights the green light with the 0.0 display if the resistance is under 2K, which is what its designers decided was a good ground.
richfinn
Well-known member
My apologies your quite correct,Technically speaking the power probe sees nothing, that was me looking at the screen with "my eyes" and deciding "oh yeah, thats a big f*cking volt drop the meter is reading 12.5v and the LED has gone red"
cheers
MrMark
Well-known member
I'm now wondering if this tool is better for power probe type checks. It has a lifetime warranty and it can be used to backprobe coils and injectors for quick checks. I don't know whether the power probe would be good that way.
http://www.amazon.com/gp/product/B0002SQV6W/?tag=atomicindus08-20
http://www.amazon.com/gp/product/B0002SQV6W/?tag=atomicindus08-20
richfinn
Well-known member
Again Im only speaking from my own real world experience with Power probes but my old PP2 would blink the green LED to confirm an injector or coil driver signal from an ECU, my newer pp3 sadly does not, and I have to use my multimeter or a noid light or if I really need to a DSO
MrMark
Well-known member
Awesome info.
Sick Puppy
Well-known member
What multimeters would be regarded as competitive brand-wise?
I mean, all we get here in NZ are 'own brand' (e.g. factory in china, only sold in 'this' particular store), Uni-T (Chinese, but at least they call it as they see it), and flukes (buy if you have both kidneys and only need one).
What else is there?
It's hard for me to answer your question because what is available to me in the US may not be available to you. Certainly Fluke, Agilent and Tektronix are all competitive brands. (With Fluke and Tektronix being Danaher owned for those who care.)
Do you want analog or digital?
I had not priced multimeters in years because my employer provided Fluke and I have two personally owned Flukes. This thread caused me to research multimeter pricing and I was quite shocked. I also was suprised to see most of the low end Fluke models discontinued.
The intent of my original message was not to discourage buying used Flukes off Ebay but rather to caution that Fluke warranty is no longer lifetime and does not pass from the original owner. If you find a used Fluke on Ebay and then should have need for repair, many repair services charge a flat rate repair price of $198 (US) for Fluke 87 and $145 (US) for Fluke 79. I have seen new Fluke 115 pricing of $159 (US). Why repair used when new (with warranty) is cheaper? Granted the Fluke 115 does not have all the bells & whistles.
There is a new Agilent display technology called OLED that does not require a backlight. It will be interesting to see if this catches on with the other manufacturers. This may be why Fluke is discontinuing so many models.
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LawnDart79
Well-known member
I've been reading where people say that Fluke's will withstand a drop from 10 feet. I recommend that nobody actually try this. About six years ago, my Fluke 88 fell from around 7 feet onto the concrete shop floor. The result was a broken case and cracked screen...and yes, i did have the yellow cover installed.
But on a bright note, the meter still works like it's supposed to. It just looks like it's been though a war zone. Although broken, it's still my main meter.
But on a bright note, the meter still works like it's supposed to. It just looks like it's been though a war zone. Although broken, it's still my main meter.
joshthedieseltech
Well-known member
- Joined
- Feb 13, 2011
- Messages
- 97
buy a fluke he first time and do it right
I went through multiple craftsman, pro, cornwell and others, they give bad readings, resistance etc.
the money i spent on the others could have bought the fluke.
I did get mine used for $150
I went through multiple craftsman, pro, cornwell and others, they give bad readings, resistance etc.
the money i spent on the others could have bought the fluke.
I did get mine used for $150
joshthedieseltech
Well-known member
- Joined
- Feb 13, 2011
- Messages
- 97
rubber shell? or not.