My vintage 80's OTC dvom died and I just got aFluke 115 dvom. Is there a calibration for the ohms setting? When I touch the 2 leads together, it reads 0.5 ohms and not 0 ohms. Leads apart, it shows OL, which O expect to see. I didn't see any 0 calibration screw. My other dvom, a 80's MAc et920 has a knob to zero the needle. Kind of difficult measure the primary resistance of an ignition coil when the spec is 0.41-0.51 ohms.
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Fluke 115 ohm calibration
- Thread starter 87GN
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bluecomputer
Well-known member
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- Jan 28, 2011
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All of the relatively recent Fluke meters are calibrated using the hole on the back side and following a specific sequence of steps with a calibrator. No manual adjustments with a screw are possible.
The Fluke 115 cannot read resistance values that low with repeatably. The 0.5 is due to the test leads and cannot be calibrated out. The Fluke 115 does not have a relative measurment feature.
To measure values that low you need a multimeter with four wire measurement.
https://en.wikipedia.org/wiki/Four-terminal_sensing
The Fluke 115 cannot read resistance values that low with repeatably. The 0.5 is due to the test leads and cannot be calibrated out. The Fluke 115 does not have a relative measurment feature.
To measure values that low you need a multimeter with four wire measurement.
https://en.wikipedia.org/wiki/Four-terminal_sensing
Thanks. Do you know of any Flukes that can read the values I need to read? It is important because if the primary resistance of the coil is too high, it pukes the ignition module. This is a Corvette transistor ignition system.
torqueman2002
Well-known member
Hmmm, the Fluke 87 has a delta button to 'zero' out the scale to account for resistance of the leads.My vintage 80's OTC dvom died and I just got aFluke 115 dvom. Is there a calibration for the ohms setting? When I touch the 2 leads together, it reads 0.5 ohms and not 0 ohms. Leads apart, it shows OL, which O expect to see. I didn't see any 0 calibration screw. My other dvom, a 80's MAc et920 has a knob to zero the needle. Kind of difficult measure the primary resistance of an ignition coil when the spec is 0.41-0.51 ohms.
I found a PDF of the 115 manual. --> http://www.manualslib.com/manual/451841/Fluke-117.html?page=4
I didn't see that feature when I did a quick read of the manual.
Maybe I just missed it.
With a good set of leads you can reduce the resistance a bit lower. A number of meters (Fluke 87 included) have a relative feature.
I'm a big fan of this family of Matco multimeters
https://www.ebay.com/itm/Matco-Tool...570.l1311.R1.TR3.TRC2.A0.H0.Xmatco+multi.TRS0
They are made by Brymen and sold under several names. I had a Greenlee version
https://www.ebay.com/itm/Multi-Test...at=0&_nkw=greenlee+multimeter&_from=R40&rt=nc
While I love higher end Flukes (87, 187) it's hard to argue against that meter for the money.
Anyway, what range of resistances are you trying to measure? If you truly need sub 1 ohm accuracy then a 4 wire is the only way to go. However, I suspect you don't really need that.
I'm a big fan of this family of Matco multimeters
https://www.ebay.com/itm/Matco-Tool...570.l1311.R1.TR3.TRC2.A0.H0.Xmatco+multi.TRS0
They are made by Brymen and sold under several names. I had a Greenlee version
https://www.ebay.com/itm/Multi-Test...at=0&_nkw=greenlee+multimeter&_from=R40&rt=nc
While I love higher end Flukes (87, 187) it's hard to argue against that meter for the money.
Anyway, what range of resistances are you trying to measure? If you truly need sub 1 ohm accuracy then a 4 wire is the only way to go. However, I suspect you don't really need that.
Anyway, what range of resistances are you trying to measure? If you truly need sub 1 ohm accuracy then a 4 wire is the only way to go. However, I suspect you don't really need that.
This is from the diagnostic flow chart:
A TI coil can be checked and identified electrically with the use of an ohmmeter. To do this, check the resistance between the two primary terminals (positive to negative). If it's a TI coil, the results should be as follows (published resistance, at 75 degrees F):
Primary to Primary .......... 0.41-0.51 ohms
My real concern is why the 115 does not got to zero when the leads are put together. Every ohm meter I've use does go to zero.
The 115 doesn't go to zero because it's actually measuring that resistance. You can try cleaning the contact surface of the leads. You can also go with gold plated leads. Fluke's standard leads are harder alloy for better wear but that means slightly higher surface contact resistance. Do you have other leads you can try or even just a bit of raw, multistrand wire jammed into the meter jacks. Bare wire should still show something like .1-.3 ohm.
Here's the other thing you can do. If you are concerned that there could be surface contact resistance, touch the meter probes to one terminal of the coil. Touch them next to each other but not actually touching. That way the resistance measurement includes the wire, probes, and terminal contact resistance. That will give you a good way to zero your reading.
Also, while you have said what a good coil reads, what does a bad coil read? Are we talking about 0.6, 6.0, 6k? If "good" basically shorted while bad is kohms I'm not sure this matters much.
Here's the other thing you can do. If you are concerned that there could be surface contact resistance, touch the meter probes to one terminal of the coil. Touch them next to each other but not actually touching. That way the resistance measurement includes the wire, probes, and terminal contact resistance. That will give you a good way to zero your reading.
Also, while you have said what a good coil reads, what does a bad coil read? Are we talking about 0.6, 6.0, 6k? If "good" basically shorted while bad is kohms I'm not sure this matters much.
It's not so much a good vs bad coil. Most of the Chinese reproduction coils do not meet the 0.41-0.51 ohm spec. If a point ignition coil, whose readings are are higher than a t.i. coil is used, it blows out the t.i. module I'm getting ready for the trip to Corvette Carlisle later this month in search of a coil. It is too easy to apply a Delco Remy transistor ignition decal onto a coil and pass it off as a t.i. coil, which sells for 4-5 times the price of a regular point coil.
bluecomputer
Well-known member
- Joined
- Jan 28, 2011
- Messages
- 65
I haven't seen a hand held milliohm meter. You can get an LCR meter that can measure down this low with 4 wire measurement but they are more complected to use. They also measure with AC not DC. These tend to be more expensive. Fluke doesn't really make this type of equipment though.
My advise is to try another set of test leads first. My Fluke 179 and the stock leads have 0.1 Ohm of resistance.
My advise is to try another set of test leads first. My Fluke 179 and the stock leads have 0.1 Ohm of resistance.
guy48065
Well-known member
Clean both ends of your leads with rubbing alcohol & a lint-free wipe, plug them in and touch them together 3 times. You should get the same reading of the actual leadwire resistance each time. If not repeatable, get new leads. But try replacing the battery first. The low-resistance function uses the most battery current and high or unstable readings are often a sign the battery is weak.
Subtract that resistance reading from your measurements. Top-of-the-line meters have a delta (aka "difference" or 'tare") button that cancels out the probe resistance for you. No magic involved--you can do the same in your head.
Subtract that resistance reading from your measurements. Top-of-the-line meters have a delta (aka "difference" or 'tare") button that cancels out the probe resistance for you. No magic involved--you can do the same in your head.
My old Tektronix TX3 has a low ohms range. You enter the function with the leads shorted and it zeros the meter by subtracting the lead resistance.
Sent from my SM-G900V using Tapatalk
All of the relatively recent Fluke meters are calibrated using the hole on the back side and following a specific sequence of steps with a calibrator. No manual adjustments with a screw are possible.
The Fluke 115 cannot read resistance values that low with repeatably. The 0.5 is due to the test leads and cannot be calibrated out. The Fluke 115 does not have a relative measurment feature.
To measure values that low you need a multimeter with four wire measurement.
https://en.wikipedia.org/wiki/Four-terminal_sensing
Sent from my SM-G900V using Tapatalk
foghorn1966
Well-known member
O.P. Between what Guy40865 & Citation are saying above., I think that they have the answers for you. I would use the same methods that they mentioned. Other than that see if there is a cal lab that rents test equip near you for a micro ohm meter to take on your hunt.
Like your handle.... T-Type owner here.
Like your handle.... T-Type owner here.
Yep. It's measuring the resistance of the leads. DMM 101. If you don't like this, get shorter leads and subtract the lead resistance from the reading for the item under test.The 115 doesn't go to zero because it's actually measuring that resistance.
I have a few of the HF freebies and they can have around an ohm. I put a heavy jumper at the socket instead of the test leads and lot of it was in the meter. Can some digital meters be zeroed?Yep. It's measuring the resistance of the leads. DMM 101. If you don't like this, get shorter leads and subtract the lead resistance from the reading for the item under test.
Sent from my SM-G900V using Tapatalk
mrjaw14
Well-known member
I have a brand new Fluke 87v that's 0.5 on the ohms scale. if you know your leads resistance, just deduct that from your measurement. 0.41 ohm should be 0.91 and 0.51 should be 1.01 if your leads have 0.5 ohm resistance
I have a few of the HF freebies and they can have around an ohm. I put a heavy jumper at the socket instead of the test leads and lot of it was in the meter. Can some digital meters be zeroed?
Sent from my SM-G900V using Tapatalk
Yes via the relative or delta button. If the meter has a resistance adjustment pot you should not adjust it to zero to subtract the probe resistance. That will result in inaccurate readings.