DMM accuracy question

[General Geoff]

Analog meters are becoming a lost tool for troubleshooting these days. There are areas where the analog shines and is a much better tool. For example, doing continuity checks, I can ring thru a huge wire bundle that terminates in a few branches, significantly faster than using a digital. Unless you need the line resistance, you only need to see a meter deflection to determine continuity. You don’t have to wait for the display to settle and stabilize on a reading. The beep function is not much of a help in high noise environments, or where the meter has to be placed at a significant distance from a user, but within eyesight.

How about just needing to see if there is any voltage on a wire... Same thing, a meter deflection is all you need. Chasing a variable voltage... Peak hold is great on the digital. Same for taking timed readings and downloading them into graphing software.

VTVM’s still out shine DMM’s for some things. One needs to select the best type tool for the need at hand.

Higher end DMMs have bar graph readouts in addition to a digital numeric readout, specifically to replicate the instant readability of an analog meter.

 

[cvairwerks]

Higher end DMMs have bar graph readouts in addition to a digital numeric readout, specifically to replicate the instant readability of an analog meter.

Ever try and read a digital display at more than arms reach in anything but perfect lighting? Doesn't take much of either bright or low light to make the display unreadable. There are times where old school is a better choice for the task. We've had instances where we have had to have a 3rd mechanic to run end to end continuity checks due to the distance between connectors being far enough apart that neither end mechanic could see the display due to washout from the hangar lights. It was also far enough that total lead resistance had to be accounted for in measurements.

A good troubleshooter will have many tools to chose from and will try and select them based on the task and conditions of use. Sometimes, you don't have the ability to chose and you have to work with what you have. We've argued for having a couple of analog meters available and the people that buy our tools can't get past buying the latest and greatest shiny things instead of what we actually want.

 

[RPH]

If the resolution of the amp clamp is not fine enough. You can wrap the conductor around the clamp arm through the center. Divide the reading by numbers of turns on clamp arm.

 

[2ndGearRubber]

You guys need to stop messing with continuity and such silliness. Put 12v on the wire with a test light, connect it to the circuit, ground the other side. Done.

If you want to be fancy, throw a clamp on it somewhere, anywhere, and confirm expected current flow. Skip the BS and 300ft of meter leads.

 

[American Locomotive]

Your meter is completely fine. The fact that it reads 0mv when you touch the leads together is evidence enough of this. It has a range of 10A - 600A

The issue is that you are down in the noise of your amp probe - those fluctuations are coming from amp clamp, not the meter. Your clamp's most sensitive mode is not good enough for what you're trying to do. You're just getting noise from its electronics.

You guys need to stop messing with continuity and such silliness. Put 12v on the wire with a test light, connect it to the circuit, ground the other side. Done.

If you want to be fancy, throw a clamp on it somewhere, anywhere, and confirm expected current flow. Skip the BS and 300ft of meter leads.

Yup, I also don't understand any situation in which someone doing continuity checks on a long run couldn't just have the meter on the end of the run they were working on, vs. the other end. Doesn't really make any sense.

 

[Rabid Badger]

Your meter is fine.

Your clamp is fine.

Neither are made for what you're trying to do.

If you want a clamp meter that will read in the mA range get a Uni-T UT210E.

 

[cvairwerks]

Yeah, lets throw 12 volts on a wire doing an end to end check, that happens to have branches into several high dollar boxes that have to remain connected. And oh yeah, it’s a 5 volt max signal line.

 

[2ndGearRubber]

Yeah, lets throw 12 volts on a wire doing an end to end check, that happens to have branches into several high dollar boxes that have to remain connected. And oh yeah, it’s a 5 volt max signal line.

5v max signal likely has insulation which will hold 12v at 1/4 amp, right?

Put whatever load at whatever voltage then if it's a 5v circuit. Then you know it can actually work. A strand of copper will have perfect continuity and not move any current, and cause voltage drops.

While my experience is automotive, idk what kind of circuit cant handle a loaded test. Just load it within the design criteria if it's a 5v sense wire. Fancy boxes should have over voltage protection built in. Never found a circuit yet that didnt. Otherwise a short between that sense wire and another power circuit would cook everything.

 

[American Locomotive]

Yeah, lets throw 12 volts on a wire doing an end to end check, that happens to have branches into several high dollar boxes that have to remain connected. And oh yeah, it’s a 5 volt max signal line.

If the wire is still connected to other devices, then you can't possibly do an accurate continuity test.

 

[richfinn]

I'm an Automotive Tech and I very rarely use ohms on my multimeters (unless I'm looking for a specific known resistance). I just use DC Volts and I can tell instantly if I have continuity/what polarity a wire is or if it's open circuit, if I want to load a circuit without the consumer attached it I use a bulb or test light.

However, I do have some extra long test leads and I like using them for some jobs where other guys might use a power probe or some such tool.

Mostly I use them if I need to sit behind the wheel of a vehicle and operate something and look at a reading on a meter or test light when nobody else is around to assist, or powering up fuel pumps etc. to move a car into a workshop.

I'm way too cheap to buy a remote display multimeter or another power probe basically (after the fifth one I swore never again)

 

[theoldwizard1]

Higher end DMMs have bar graph readouts in addition to a digital numeric readout, specifically to replicate the instant readability of an analog meter.

The big benefit of old analog meters was not reading them. It was the fact that they were low impedance and actually put a small load on the circuit. This is why INCANDESCENT test lights are still valuable.

If you didn't understand what I just said, go take a test year college physics course?

 

[theoldwizard1]

If you want a clamp meter that will read in the mA range get a Uni-T UT210E.

I have one. I would not trust it's accuracy more than +/- 10%

 

[theoldwizard1]

However, I do have some extra long test leads and I like using them for some jobs where other guys might use a power probe or some such tool.

Ivan from Pine Hollow Auto Diagnostics regularly use the power leads from his Power Probe, connected directly to the battery, so he knows he has a "good ground and a good 12V reference".

 

[2ndGearRubber]

I'm an Automotive Tech and I very rarely use ohms on my multimeters (unless I'm looking for a specific known resistance). I just use DC Volts and I can tell instantly if I have continuity/what polarity a wire is or if it's open circuit, if I want to load a circuit without the consumer attached it I use a bulb or test light.

However, I do have some extra long test leads and I like using them for some jobs where other guys might use a power probe or some such tool.

Mostly I use them if I need to sit behind the wheel of a vehicle and operate something and look at a reading on a meter or test light when nobody else is around to assist, or powering up fuel pumps etc. to move a car into a workshop.

I'm way too cheap to buy a remote display multimeter or another power probe basically (after the fifth one I swore never again)

The issue with ohms, is it only has value if the test fails. If something passes the ohm test, that means nothing. Kind of like a headgasket test with the blue fluid. If it fails, it fails. If the fluid doesn't change color or it might have maybe changed a little - it's inconclusive. Where as in less time, I can hook up a pressure transducer to the cooling system via the cap/bottle, and run the engine for 10 seconds. Building pressure? She's blown captain. Really cooked ones will build a couple PSI cranking. LOL

If something is super easily accessible, and you have a good idea what the number should be, it's worth a shot. Another one I like is spark plug testing for light misfires, GM v8s are a great example. OHMs scale, plug top to ground, if it's anything but open it's fouled. No need to remove anything aside the plug wire to coil connection. Yes, hydrocarbon fouling is possible, but if that was the case it would have a severe miss and other methods would be utilized. Fuel isn't going to be saturating the plug on any cylinder that has a significant instance of combustion. This is for those BS fish-bite tiny misfires that happen once every 30seconds or more. Of course, you could just check fuel trims, current ramp the coils, and sell plugs based on process of elimination. Very rarely will that method lead you astray. Although a hyundai with a torn intake gasket and fuel trims under 5% ate my lunch one time on that.


At the risk of poking at anybody, ohm testing is the preferred method of people and organizations who do not understand circuits and the real world requirements of testing. It's like manufacturer flow charts, they ****. Super inefficient, poor use of available scan data, poor choice of process order, etc.


I too am one for long leads, I could do end to end ohm tests on a car if I wanted. But it's a poor choice of test method.

 

[richfinn]

Ivan from Pine Hollow Auto Diagnostics regularly use the power leads from his Power Probe, connected directly to the battery, so he knows he has a "good ground and a good 12V reference".

It works very well on modern European vehicles where they hide everything behind ****** plastic covers and like to stick the battery in the trunk, the extension cable in the power probe kit is probably the best part to honest if you have 4mm banana Jack's on your test equipment, if I need to add a fuse I just run it through my amp jack on the multimeter.

I have some 20amp rated silicone insulated twin core cable with stackable plugs at each end about 8 metres long (good for vans etc.)

 

[Rabid Badger]

I have one. I would not trust it's accuracy more than +/- 10%

....and?

It's a DC current clamp. By definition it's readings are going to change slightly depending on the environment, whether the meter is rotated in relation to the conductor, etc.

You can spend 5 times as much for a meter with a smaller hole through the clamp to restrict the movement of the conductor. Your reward? Instead of reading 18-22mA on a conductor carrying 20mA, you'll see 19-21mA.

 

[richfinn]

The issue with ohms, is it only has value if the test fails. If something passes the ohm test, that means nothing. Kind of like a headgasket test with the blue fluid. If it fails, it fails. If the fluid doesn't change color or it might have maybe changed a little - it's inconclusive. Where as in less time, I can hook up a pressure transducer to the cooling system via the cap/bottle, and run the engine for 10 seconds. Building pressure? She's blown captain. Really cooked ones will build a couple PSI cranking. LOL

If something is super easily accessible, and you have a good idea what the number should be, it's worth a shot. Another one I like is spark plug testing for light misfires, GM v8s are a great example. OHMs scale, plug top to ground, if it's anything but open it's fouled. No need to remove anything aside the plug wire to coil connection. Yes, hydrocarbon fouling is possible, but if that was the case it would have a severe miss and other methods would be utilized. Fuel isn't going to be saturating the plug on any cylinder that has a significant instance of combustion. This is for those BS fish-bite tiny misfires that happen once every 30seconds or more. Of course, you could just check fuel trims, current ramp the coils, and sell plugs based on process of elimination. Very rarely will that method lead you astray. Although a hyundai with a torn intake gasket and fuel trims under 5% ate my lunch one time on that.


At the risk of poking at anybody, ohm testing is the preferred method of people and organizations who do not understand circuits and the real world requirements of testing. It's like manufacturer flow charts, they ****. Super inefficient, poor use of available scan data, poor choice of process order, etc.


I too am one for long leads, I could do end to end ohm tests on a car if I wanted. But it's a poor choice of test method.

I can't remember the last time I actually measured ohms, probably a fuel injector or a relay coil.

I sometimes use the continuity beeper on immobiliser/door lock wiring as they have started to use all black wires to stop thieves stealing them, or Peugeot and Citroën where they use ridiculous tiny printed code numbers on the insulation instead of proper coloured wiring

 

[richfinn]

The issue with ohms, is it only has value if the test fails. If something passes the ohm test, that means nothing. Kind of like a headgasket test with the blue fluid. If it fails, it fails. If the fluid doesn't change color or it might have maybe changed a little - it's inconclusive. Where as in less time, I can hook up a pressure transducer to the cooling system via the cap/bottle, and run the engine for 10 seconds. Building pressure? She's blown captain. Really cooked ones will build a couple PSI cranking. LOL

If something is super easily accessible, and you have a good idea what the number should be, it's worth a shot. Another one I like is spark plug testing for light misfires, GM v8s are a great example. OHMs scale, plug top to ground, if it's anything but open it's fouled. No need to remove anything aside the plug wire to coil connection. Yes, hydrocarbon fouling is possible, but if that was the case it would have a severe miss and other methods would be utilized. Fuel isn't going to be saturating the plug on any cylinder that has a significant instance of combustion. This is for those BS fish-bite tiny misfires that happen once every 30seconds or more. Of course, you could just check fuel trims, current ramp the coils, and sell plugs based on process of elimination. Very rarely will that method lead you astray. Although a hyundai with a torn intake gasket and fuel trims under 5% ate my lunch one time on that.


At the risk of poking at anybody, ohm testing is the preferred method of people and organizations who do not understand circuits and the real world requirements of testing. It's like manufacturer flow charts, they ****. Super inefficient, poor use of available scan data, poor choice of process order, etc.


I too am one for long leads, I could do end to end ohm tests on a car if I wanted. But it's a poor choice of test method.

When I was an apprentice (a long time ago) my boss used to have an old school version of your test for head gaskets that would pinpoint where the gasket had failed.

1. Remove fan/water pump belt (stops the coolant moving)

2. Remove spark plugs

3. Fill radiator right up to the brim of the filler neck and leave cap off

4. Crank engine for a few seconds replacing one spark plug at a time

When you found the leaking cylinder the radiator would overflow
(needless to say things were more accessible in engine bays back then)

He learned this trick as a Mechanic in the British Army during WW2

 

[cvairwerks]

If the wire is still connected to other devices, then you can't possibly do an accurate continuity test.

In a circuit that has multiple "T" branches, you sure can do a continuity check. If you need a resistance check, no, it will not work. For what we do, most of the time, all we need to know is if there is an electrical path down the wire between two harness pins. Other times we do need to know the total path resistance, sometimes we are given what we should see with the boxes connected and other times, we have to disconnect everything looking for specific faults. There are times we also have to disconnect everything on the circuit and run TDR checks when certain faults can't be found by conventional testing, such as breaks in harness runs that are between isolation points.

 

[Showkey]

Yeah, lets throw 12 volts on a wire doing an end to end check, that happens to have branches into several high dollar boxes that have to remain connected. And oh yeah, it’s a 5 volt max signal line.

Done wrong …….your FUCKED…………..very similar to using a power probe, randomly applying ground or power (12v) to certain wires like CAN or signal/sensor wires can damage modules.

Happens all the time when the wrong connector cavity is probed or just when things are done wrong.

Agree the resistance reading on wiring with no load if often a waste of time. If you know the circuit and all it’s branches etc the power load is valid and useful.

Very seldom is couple for tenths in a reading a DVOM the difference between good and bad. Especially if it’s a comparison reading using the same meter as the comparison. Both reading are off the same amount.

The knowledge and skills of the user is far more important than the quality or price of the meter with the criteria the meter is working and makes consistent readings.

 

[richfinn]

Done wrong …….your FUCKED…………..very similar to using a power probe, randomly applying ground or power (12v) to certain wires like CAN or signal/sensor wires can damage modules.

Happens all the time when the wrong connector cavity is probed or just when things are done wrong.

Agree the resistance reading on wiring with no load if often a waste of time. If you know the circuit and all it’s branches etc the power load is valid and useful.

Very seldom is couple for tenths in a reading a DVOM the difference between good and bad. Especially if it’s a comparison reading using the same meter as the comparison. Both reading are off the same amount.

The knowledge and skills of the user is far more important than the quality or price of the meter with the criteria the meter is working and makes consistent readings.

I've never really bought into that, module's are pretty well designed in case
wires accidentally short to power or ground through chafed wiring etc.

If I'm looking at the 5v ref (sensor power supply) I use a ref box similar to this

5V Reference Box | Jarhead Diagnostics

The 5V reference box is a versatile automotive diagnostic tool that allows you to power 5V circuits, sensors and components to conduct electronic diagnostics. It can also be used to operate a pressure transducer for conducting in-cylinder diagnostics.

www.warwickts.com

 

[2ndGearRubber]

Done wrong …….your FUCKED…………..very similar to using a power probe, randomly applying ground or power (12v) to certain wires like CAN or signal/sensor wires can damage modules.

Happens all the time when the wrong connector cavity is probed or just when things are done wrong.

Agree the resistance reading on wiring with no load if often a waste of time. If you know the circuit and all it’s branches etc the power load is valid and useful.

Very seldom is couple for tenths in a reading a DVOM the difference between good and bad. Especially if it’s a comparison reading using the same meter as the comparison. Both reading are off the same amount.

The knowledge and skills of the user is far more important than the quality or price of the meter with the criteria the meter is working and makes consistent readings.

So dont dump unregulated power/ground into a circuit. Use a load like a test light as a restriction. My standard low current bulbs are 250ma. You can stick that right on a CAN line and you'll be fine. Dont recommend, you'll set network codes, but the network will live. Of course, most networks used twisted pairs of wires, so there should be little margin for mistakes there. The visual of twisted wires will say you're on the wrong circuit. Network continuity is best tested with a scan tool as a first step. Who talks?

Just going full retard with a power probe isnt suggested. Know the equipment you're using.

 

[Showkey]

I've never really bought into that, module's are pretty well designed in case
wires accidentally short to power or ground through chafed wiring etc.

If I'm looking at the 5v ref (sensor power supply) I use a ref box similar to this

5V Reference Box | Jarhead Diagnostics

The 5V reference box is a versatile automotive diagnostic tool that allows you to power 5V circuits, sensors and components to conduct electronic diagnostics. It can also be used to operate a pressure transducer for conducting in-cylinder diagnostics.

www.warwickts.com

Ground the ECU power out to the purge control valve on some brands ……….get back to us on the cost of the ECU …..cuz the driver is toast.

 

[Showkey]

So dont dump unregulated power/ground into a circuit. Use a load like a test light as a restriction. My s

Just going full retard with a power probe isnt suggested. Know the equipment you're using.

Novices, DIY and pros make errors all the time………..bad practice or habits are unforgiving.

In factory training center environment we banned power probes………literally 100’s of modules toasted because troubleshooting errors. It’s not the cost of the modules it was the bad habits that cause problems in real life.

 

[cvairwerks]

Outside of some sensors, a few boxes and things like switches and motors, nearly everything we touch is either ESD sensitive, operates submerged in jet fuel or is connected to explosives.....No way I'd hack around with something that wasn't approved for use by engineering.

Want to see the results of using hacked test equipment on critical systems? Look up KC-135 overpressure failure. Shop was using a hacked pressure gauge and was 1 of 2 links in the chain resulting the complete destruction of the aircraft.

Rarely going to be a problem working on ground vehicles, but one needs to be cognizant of what can happen when things go sideways...

 

[richfinn]

Ground the ECU power out to the purge control valve on some brands ……….get back to us on the cost of the ECU …..cuz the driver is toast.

I've never smoked a module in 37yrs of being an Auto tech/Auto Electrician.

I don't use powerprobes anymore because they are just flimsy toys in my experience.

Just use an incandescent test lamp instead and your worries are solved
(I know the manufacturers hate it, but I don't care, their training is generally slow witted bullsh*t anyway)

Nearly all the dead modules I've come across have been water ingress or spiked due to jump starts or bad ignition coils burning out the drivers, or sometimes wipeouts from zero battery support during programming

 

[2ndGearRubber]

Novices, DIY and pros make errors all the time………..bad practice or habits are unforgiving.

In factory training center environment we banned power probes………literally 100’s of modules toasted because troubleshooting errors. It’s not the cost of the modules it was the bad habits that cause problems in real life.

Test light does what the power probe does, safer. I know lots of people dislike power probe, I very rarely use mine. If the circuit breaker was set lower, like 500ma, it would be much less dangerous. I can see the reason OEMs wouldn't like them.

Although most OEMs wont use a labscope either. Working without scopes, test lamps, and yes even the occasional power probe, is a massive loss IMO. But I dont own a car brand, so nobody cares about my thoughts on troubleshooting manuals the OEMs write.

 

[emoze]

thanks to all for the education - i have been studying the accuracy-vs-range-vs-resolution issue - i am admittedly a novice on this topic

Maybe an ANSWER - the newer 88V has a HiRes 4-1/2 digit mode on almost all scales vs my old 88 which is HiRes for ohms only (but still the maybe problematic 600mV range) - guess it's time to upgrade (tough to spend $500 for something i will rarely use, ..... so it goes)

Also noted - the Innova 3347 clamp has 1mv/A & 10mV/A ranges (similar to that UT210e above), versus my AES 695 which has 10mV/A & 100mV/A ranges

 

[billford]

I have a fluke 88 and 2 fluke amp clamps, 80i-110S and 610S. Both have their place but not for parasitic draws.

I bought this Uni T for quick testing parasitic draws. It reads down to .001 amps but fluctuates on d/c a bit if you move the clamp around. If you keep it steady, its ok once you zero it. Its good enough for testing draws and much more compact than using a separate multimeter and amp clamp.

My favorite parasitic draw tool is the snap-on vantage MT2400.

 

[American Locomotive]

thanks to all for the education - i have been studying the accuracy-vs-range-vs-resolution issue - i am admittedly a novice on this topic

Maybe an ANSWER - the newer 88V has a HiRes 4-1/2 digit mode on almost all scales vs my old 88 which is HiRes for ohms only (but still the maybe problematic 600mV range) - guess it's time to upgrade (tough to spend $500 for something i will rarely use, ..... so it goes)

Also noted - the Innova 3347 clamp has 1mv/A & 10mV/A ranges (similar to that UT210e above), versus my AES 695 which has 10mV/A & 100mV/A ranges

No, that is not the answer. Your multimeter has more than enough resolution. The issue is your Innova 3347 doesn't have enough sensitivity to do what you want. You could put that thing on a 7 1/2 digit lab-grade voltmeter, but at 10-30mA measured current it's still going to give you meaningless numbers that are bouncing around. Even 100 mv/A is going to be iffy with ANY DMM trying to measure in the mA range.

 

[emoze]

I have a fluke 88 and 2 fluke amp clamps, 80i-110S and 610S. Both have their place but not for parasitic draws.

I bought this Uni T for quick testing parasitic draws. It reads down to .001 amps but fluctuates on d/c a bit if you move the clamp around. If you keep it steady, its ok once you zero it. Its good enough for testing draws and much more compact than using a separate multimeter and amp clamp.

thanks - per another similar recommendation i just ordered the UniT pro

 

[Citation]

thanks to all for the education - i have been studying the accuracy-vs-range-vs-resolution issue - i am admittedly a novice on this topic

Maybe an ANSWER - the newer 88V has a HiRes 4-1/2 digit mode on almost all scales vs my old 88 which is HiRes for ohms only (but still the maybe problematic 600mV range) - guess it's time to upgrade (tough to spend $500 for something i will rarely use, ..... so it goes)

Also noted - the Innova 3347 clamp has 1mv/A & 10mV/A ranges (similar to that UT210e above), versus my AES 695 which has 10mV/A & 100mV/A ranges

Don't bother with a new meter. No reason to spend that kind of money to replace your older 88 with a new of just to get a bit more accuracy.

What you need is either a lower current clamp meter attachment or an external attachment or a shunt for current measurement. Then again if you know the current draw is low (ie won't blow the $10 fuse in your meter) just run the current through the meter.

 

[emoze]

No, that is not the answer. Your multimeter has more than enough resolution. The issue is your Innova 3347 doesn't have enough sensitivity to do what you want. You could put that thing on a 7 1/2 digit lab-grade voltmeter, but at 10-30mA measured current it's still going to give you meaningless numbers that are bouncing around. Even 100 mv/A is going to be iffy with ANY DMM trying to measure in the mA range.

thanks - saves me $500!

the question of various clamp measuring scales/output has me puzzled - need more education on that - ? which is the most sensitive & useful clamp output scale for mV to mA conversion readout? Innova's 1mV/A or 1mV/100mA; AES's 10mV/A or 100mV/A ???

- seems like every brand of clamp is different (iirc i read somewher that Innova 1mV/100mA scale is a direct readout to mA conversion, which seemed like it would be quite useful ?? - but per above is still irrelevant)

'yup - i watched too many u-tubes about how wonderful the amp clamps are!

 

[billford]

Then again if you know the current draw is low (ie won't blow the $10 fuse in your meter) just run the current through the meter.

But that doesn't help you trace the current flow through a harness. With a amp clamp, you can just quickly clamp around any harness to see the current flow. The only limitation is when power and ground are in the same harness bundle and cancel each out out.

 

[emoze]

But that doesn't help you trace the current flow through a harness. With a amp clamp, you can just quickly clamp around any harness to see the current flow. The only limitation is when power and ground are in the same harness bundle and cancel each out out.

thanks - i was originally dealing with a 'too high' parasite draw, but well under the meter's current capacity

- my self induced problem was in trying to come up with alternative to disconnecting the battery & upsetting the computer & the back-ups & waiting for it all to reset whilst trying to find the high-draw circuit - i tried the fuse-volt-drop technique with little success so decided to buy/try amp-clamps, along with fuse-buddy current-loop kit)

(( the whole project is temporarily moot cuz somehow in the last 2 weeks the draw went away (after much physical disconnecting of suspect circuits, re-testing, & re-connecting it all) ! - i still want to have all the right tools ready for the probable repeat chapter or next car - 'way too many potentially causative circuits on just one fuse; (fyi- a Honda) - a clamp solution would certainly make things easier than singularly disconnecting wires behind the fuse panel as the Honda manual suggests as a last resort))

 

[Wrench97]

You can't really just clamp it around any harness since you would have to know what in that harness was powered up and which direction it's traveling.
Trying to get access to single wires coming out of a Honda fuse box can be problematic as well, looking for down stream connectors or find the end of line device may be easier sometimes, if it's a minivan it's probably the power slide doors...........................................

 

[emoze]

You can't really just clamp it around any harness since you would have to know what in that harness was powered up and which direction it's traveling.
Trying to get access to single wires coming out of a Honda fuse box can be problematic as well, looking for down stream connectors or find the end of line device may be easier sometimes, if it's a minivan it's probably the power slide doors...........................................

agreed - i only wanted to clamp on individual wires -
'yep - know about the honda door lock issues - tearing off all 4 door panels to check those is a last resort i was hoping to avoid (already replaced one lock assy, but that one was easy to diagnose ) - i still have to do the DTC diagnosis & maybe a code will still be there - just got the "special jumper tool" for use in upper fuse-box location behind the lkick panel

 

[American Locomotive]

thanks to all for the education - i have been studying the accuracy-vs-range-vs-resolution issue - i am admittedly a novice on this topic

Maybe an ANSWER - the newer 88V has a HiRes 4-1/2 digit mode on almost all scales vs my old 88 which is HiRes for ohms only (but still the maybe problematic 600mV range) - guess it's time to upgrade (tough to spend $500 for something i will rarely use, ..... so it goes)

Also noted - the Innova 3347 clamp has 1mv/A & 10mV/A ranges (similar to that UT210e above), versus my AES 695 which has 10mV/A & 100mV/A ranges

thanks - saves me $500!

the question of various clamp measuring scales/output has me puzzled - need more education on that - ? which is the most sensitive & useful clamp output scale for mV to mA conversion readout? Innova's 1mV/A or 1mV/100mA; AES's 10mV/A or 100mV/A ???

- seems like every brand of clamp is different (iirc i read somewher that Innova 1mV/100mA scale is a direct readout to mA conversion, which seemed like it would be quite useful ?? - but per above is still irrelevant)

'yup - i watched too many u-tubes about how wonderful the amp clamps are!

1mv/100ma is the same thing as 10mv/A.

100mv/A is the same thing as 0.1mv/1mA.

1000mV/A is the same thing as 1mV/mA.

To measure mA with a clamp probe connected to a scope or DMM, you would realistically need a probe with 1000mV/A sesnsitivity.

 

[richfinn]

The trouble is a decent current probe with the accuracy you desire has very small jaws (not great for battery cable).

This is the main reason most techs just run it through the amp jack on the multimeter.

You can fit a fused link between the battery post and battery terminal and clamp around that, but you still have to unhook the battery at some point.

The Uni-T 210e will work fine the only thing is you will have to latch the hood manually with it open so you can still read the meter.

I sometimes use my extra long meter leads to link the battery terminal (with a fuse I made that has 4mm plugs) I can then hook the clamp meter around the lead and take it to any point on the vehicle with the hood closed and work on the fuse boxes

 

[billford]

Some people here are bashing ohms testing.
Working on the rainy west coast, I find ohms very useful for circuit insulation. After isolating the suspect circuit and checking for a path to ground or to other circuits. Any reading indicates a problem.