Help with fluke 289 Please

[ehcaes]

Hi Im a newbie to electronics and just decided it was time to do away with my old cheap one and got this 289 off ebay apparently brand new for a good price, Funny thing is when I turn it on the meter reading on dc volts jumps up and down like a yoyo so do other settings is this normal? I would have thought it would happily sit on 0 and wait for me to take a reading, like my old cheap one. when I set it to ohms and hold the probes together and rel out on dc volts it keeps going from 1 to 0 and if i move the meter or press the screen it really starts goin up in reading to like 50 volts and back?

Confused.

[thilo]

Congratulations. Have you tested the meter on some voltages, resistors, diodes, currents, etc? For a good meter it's normal to display something else than 0 (on some ranges). I think the getting started manual from fluke explains for every measurement option what you should see on the display if everything is ok.

50 Volts with nothing connected to the probes does not sound like a healthy meter, or environment.  But for now don't worry about the display too much, test it on some known values, like batteries, lab power supply, function generator, resistors, diodes, etc. and if the readings are about what you'd expect it should be fine. And read the (getting started) manual.




Thilo.

[ehcaes]

Thanks for the reply will your ideas when I said 50 volts its actually 0.00529 or something silly mistake that 2 used to reading the old cheapo I guess.

[thilo]

In that case it's perfectly fine. It's normal that such a sensitive meter picks up some millivolt noise through the probes which work like antennas. But still go and do some basic sanity checks to be reasonably sure that it's really working. There's nothing more annoying than broken test gear when you're trying to debug your circuit and chase phantom errors.

[Tony R]

Ok yes it is just a sensitive meter and is picking up noise, but to explain this lets think of what voltage means a volt is a unit of electric potential difference between two points. if your probes are hanging in the air they are measuring two points in space and we are surrounded by a ton of electric fields, everything from the sun, core of the earth, computers, electric wires in our homes, produce electromagnetic fields. These fields change values over space and time. You also pick up noise from the probes picking up on magnetic fields though space. Try touching the tips together and you should get a very low value (less than a mV) being they are essentially measuring the same point to space there is no difference in the electric field. But why is their a small value on my meter? Well one cause is now you have a loop what picks up signals like coil in a changing magnetic field... well that is kinda what it is this induces a current, and where there is a current, there is a voltage (I=V/R). This can all be solved by touching the probes and re zeroing it or hitting the relative button.

The way i figure it, the last digit of any test equipment is generally unreliable so take it for what its wroth (I usually round the next place and toss the last value)

[IanB]

Try touching the tips together and you should get a very low value (less than a mV)

It definitely should read exactly zero in this case, or your meter is kaput!

[ehcaes]

Thanks Guys, all very helpful replies  .Here is where im currently at, after doing some basic tests with a few resistors diodes and batterys  which all checked out ok. I have 2 different settings for ohms there is the high ohms I assume and a low ohms setting. on high ohms touching the probes together I get about 0.14 if i hit the relative button I get exactly zilch and the reference below the main reading shows 0.000, When I do the same thing on the low ohms setting i get about 0.105 and slightly fluctuates which I assume would be the electro magnetic effect If I hit relative I get zero however the reference below still shows a low reading where the high setting shows nothing??? Im assuming this is normal just makes no sense when 1 setting contradicts the other.

Daniel.

[Kiriakos-GR]

I was not aware that the Fluke 289 behaves in the ohms mode identically with the 87V & 28II,
in this case this thread it will help you.
https://www.eevblog.com/forum/index.php?topic=3879.0 

[ejeffrey]

Low ohm is just the lowest resistance range.  I don't know why in particular it is only available as a manual range -- either they are changing the way the excitation current is applied or switching in an extra amplifier before the voltage measurement.  Or both.

In any case, DMMs generally specify the accuracy on ohms mode after using relative mode.  The only exception are cheap low resolution models with no rel mode.  This is because two-wire resistance measurements include the resistance of the probes and the contact resistance, and possibly anything else in the signal path.  Hit the rel button and you should be good to go, although with any 2-wire ohms measurement you will be limited by the variation in the contact resistance where the probes touch the device under test.

[ehcaes]

I was not aware that the Fluke 289 behaves in the ohms mode identically with the 87V & 28II,
in this case this thread it will help you.
https://www.eevblog.com/forum/index.php?topic=3879.0 

Very interesting, double checked against those readings and getting exactly the same, Strange fluke has a flash rom for upgrading the firmware, and gives credit to Dave's comment regarding it and what hidden bugs there might be in his 189/289 review. Wonder why fluke haven't addressed this bug yet I checked my firmware and its ver 1.12 / v0.88 whats stranger is I could only find ver 1.11 on flukes website.

[Alex]

do away with my old cheap one and got this 289 off ebay apparently brand new for a good price

Time for a new flagship DMM Fluke.

I was not aware that the Fluke 289 behaves in the ohms mode identically with the 87V & 28II,
in this case this thread it will help you.
https://www.eevblog.com/forum/index.php?topic=3879.0 

Very interesting, double checked against those readings and getting exactly the same, Strange fluke has a flash rom for upgrading the firmware, and gives credit to Dave's comment regarding it and what hidden bugs there might be in his 189/289 review. Wonder why fluke haven't addressed this bug yet I checked my firmware and its ver 1.12 / v0.88 whats stranger is I could only find ver 1.11 on flukes website.

There was nothing wrong with the meter there, just meter capabilities as stated in the manual combined with Kyriakos taking measurements after having oily fish for dinner.   The specs are different for the 289 in the normal Ohms and LowOhm modes. The reading you are seeing is primarily the resistance of leads and connections. The LowOhms range will give you a less inaccurate reading of this resistance. Relative mode will substract the reading when the button was pressed from each subsequent reading, effectively cancelling the error from lead resistance.

Wonder why fluke haven't addressed this bug yet I checked my firmware and its ver 1.12 / v0.88 whats stranger is I could only find ver 1.11 on flukes website.

For a very long time I could not find the firmware upgrade on the UK Fluke site unless I was selectively blind. I had to download it from the US site and yes, I did come across it by actively looking for it as opposed to being informed about it after registering the DMM. Maybe they are rolling it out as a very low priority.

[Kiriakos-GR]

There was nothing wrong with the meter there, just meter capabilities as stated in the manual combined with Kyriakos taking measurements after having oily fish for dinner.  

I was aware that we have some Fluke fun boys around,
but this one has a Neon bright arrow over his head pointing down to him.     

[ehcaes]

Thats a real pita if your gotta rel out every time you wanna measure something. Surely fluke will address this in their next firmware?

I was aware that we have some Fluke fun boys around,
but this one has a Neon bright arrow over his head pointing down to him.     

not sure what that means??? im just new to this meter and electronics so forgive me if I sound like an idiot.

[Joshua]

I believe he was talking to Alex

My fluke usually has small values like yours but I just forget about it because what I'm measuring is not super high precision. For instance, if I'm measuring a 10k 5% resistor, it could actually be 9500 ohms and be in spec. I ain't gonna worry 'bout no milliohms with that.

Now, if I happen to measure something that I need a value down to a couple of decimal places, sure I'll rel it out, but that is very rarely.

Just my thoughts. I'm a newb 2 so take that with a grain of salt. 

[thilo]

Thats a real pita if your gotta rel out every time you wanna measure something. Surely fluke will address this in their next firmware?

Be aware that the test lead resistance is typically around 200 Milliohms, or 0.2 Ohms. For a 100 Ohms resistor thats an error of 0.2%. For 500 Ohms it's already down to 0.04%, that's below the measurement accuracy of the meter itself! Bottom line: unless you need to do some high precisions measurements for resistors with resistances up to ~100 Ohms the test lead error is not significant. For everything else use 4-wire measurements and read http://www.keithley.com/data?asset=55835



Thilo

[ejeffrey]

Thats a real pita if your gotta rel out every time you wanna measure something.

Only if you want to measure to 100 milliohm accuracy.  On the higher ranges, the contact resistance is negligible.