EEVblog® Electronics Community Forum
Products => Test Equipment => Topic started by: Axtman on April 24, 2017, 06:26:57 am
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When did they start putting built-in thermometers in Fluke 87 V multimeters?
It is the second item down on the features tab on the Fluke page:
http://en-us.fluke.com/products/digital-multimeters/fluke-87v-digital-multimeter.html#features (http://en-us.fluke.com/products/digital-multimeters/fluke-87v-digital-multimeter.html#features)
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Every meter that can read the temperature of a thermocouple has a built-in thermometer. When determining the thermocouple reading the meter has to measure the temperature of the reference junction inside the meter, and to do this it needs an internal thermometer.
You can make a meter display the internal temperature by shorting out the input terminals instead of plugging in a thermocouple. Some meters will do this automatically when no thermocouple is plugged in, but many don't.
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Its seems a bit wierd. Who asked the meter to compare 2 readings? Is all you want is to have the meter read the value at the K type thermocouple which is a standard value across all K type thermocouple.
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The thermocouple asked the meter to compare two readings because that's how thermocouples work. A thermocouple does not measure the junction temperature, it measures the difference in temperature between two junctions. One junction is placed at the point to be measured, and the other junction is placed at some known reference temperature. The EMF generated by the thermocouple is a function of the difference in temperature between the two junctions. Therefore if the temperature of the reference junction is known the temperature of the measurement junction can be determined.
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Every meter that can read the temperature of a thermocouple has a built-in thermometer. When determining the thermocouple reading the meter has to measure the temperature of the reference junction inside the meter, and to do this it needs an internal thermometer.
You can make a meter display the internal temperature by shorting out the input terminals instead of plugging in a thermocouple. Some meters will do this automatically when no thermocouple is plugged in, but many don't.
My 87V (acquired in2010) displays OPEn when the thermo probe is not plugged in. It has always been this way, and makes temperature readings perfectly well when the probe is inserted. I have had other meters which do have the internal temperature reference.
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The Fluke 185 always shows cold junction temperature on the upper display.
On the main display, with decimal:
1. No probe, cold junction temperature
2. Probes open or shorted, cold junction temperature
3. K-type thermocouple, hot junction temperature
There is a procedure to zero the thermocouple voltage offset, by first immersing its bulb in an ice bath, to increase the accuracy of all further measurements.
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Every meter that can read the temperature of a thermocouple has a built-in thermometer. When determining the thermocouple reading the meter has to measure the temperature of the reference junction inside the meter, and to do this it needs an internal thermometer.
I'm pretty sure that wasn't the OP's actual question. I'm pretty sure they just wanted to know when the Fluke 87 series gained the temperature feature.
When did they start putting built-in thermometers in Fluke 87 V multimeters?
It is the second item down on the features tab on the Fluke page:
http://en-us.fluke.com/products/digital-multimeters/fluke-87v-digital-multimeter.html#features (http://en-us.fluke.com/products/digital-multimeters/fluke-87v-digital-multimeter.html#features)
Am I right that your question wasn't about an internal thermometer for cold-junction compensation, but rather "built-in thermometer" meaning that it can take temperature measurements without a separate instrument? This was added to the 87V. Older versions of the 87 didn't have the thermometer feature.
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My 87V (acquired in2010) displays OPEn when the thermo probe is not plugged in. It has always been this way, and makes temperature readings perfectly well when the probe is inserted. I have had other meters which do have the internal temperature reference.
If it's able to measure the absolute temperature of the thermocouple's tip, it has to have the cold junction compensation inside the meter in one form or the other. There's no way around that - that's how thermocouples work. Without that, all your meter could tell you would be "the thing you're probing is x degrees hotter/colder than where I'm sitting".
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I'm sorry but I should have explained what lead up to my question.
I kept hearing and reading that the Fluke 87 V had a built-in thermometer. This feature is even described on Fluke's model features page. I bought my used Fluke multimeter several years and of course it did not come with a manual. I know that Fluke does occasionally update the multimeter, for example they fixed the mobile phone interference issue. So if figured that they added the built-in thermometer (and maybe other features) but did not change the model number.
Whenever I switched my multimeter to temperature range the display would indicate "OPEn", which I assumed was shorthand for, "Hey stupid! Plug in a K-type probe!" Nowhere in the online manual (May 2004 Rev.2, 11/08) does it indicate that by shorting the leads you can get temperature reading. (Thanks for the tip IanB!)
I will write Fluke and ask them to revise their literature to reflect this feature, so other people like me do not get confused.
Thanks again for great discussion.
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Whenever I switched my multimeter to temperature range the display would indicate "OPEn", which I assumed was shorthand for, "Hey stupid! Plug in a K-type probe!" Nowhere in the online manual (May 2004 Rev.2, 11/08) does it indicate that by shorting the leads you can get temperature reading. (Thanks for the tip IanB!)
I will write Fluke and ask them to revise their literature to reflect this feature, so other people like me do not get confused.
They haven't mentioned that in the manual because that's more of a "side-effect" (or "added bonus" if you will) than a feature, really.
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I think the only people being confused are those who are overthinking it because they know about cold-junction compensation.
When everyone says that the 87V has a built-in thermometer, all that's meant is "you can plug in a thermocouple to measure temperature", as opposed to needing a separate device. (Yes, the OPen display absolutely does mean "plug in your damned thermocouple!") The fact that you can short the input and see something approximating ambient temperature is neither a feature nor a bug, it's just a characteristic of thermocouple thermometers. There's NOTHING to indicate that some 87V implement the thermometer function differently, since they ALL use a type-K thermocouple. So don't think that some revisions have an internal cold-junction compensation and some don't.
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Some meters always display the cold junction temperature, whether a K-type thermocouple is connected or not. It is documented and is a feature.
In all meters, the measurement is taken close to the reference junction (ambient), with a thermistor, RTD, thermal diode or temp sensor IC.
Once the thermocouple is plugged in, that temperature is used for cold junction compensation.
The hot junction temperature can then be calculated, using voltage and look-up tables (or formulae) to compensate for non-linearity.
Shorting the probes, mimics a thermocouple with no induced voltage and the meter only displays the remaining cold junction temperature with its compensation (ambient).
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We know this. The point is that that's not what Fluke is talking about when they say 'built-in thermometer'. All they mean is that you can plug a thermocouple probe in. Repeating this detail is only going to confuse our already-confused OP even further.
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'Built-in thermometer conveniently allows you to take temperature readings without having to carry a separate instrument'
The OP doesn't seem to know how temperature is measured with a multimeter.
Fluke wrote a confusing statement. One needs a separate instrument or tool called a thermocouple to measure the temperature of a DUT.
Shorting the probes, will mimic a thermometer to display ambient temperature pretty accurately, without the use of a thermocouple.
There is nothing to be confused about, once you know how the damned thing works!
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Obviously I am confused. Thus the reason for my question.
I have another multimeter where when I turn the dial to (degF / degC) it would display the ambient room temperature. When you instert a K-thermocouple you get a specific temperature for the item being measured. I had mistakenly assumed that my Fluke meter (or a newer version) would operate the same way.
On occasion I have to be out on job site and I need to report weather conditions. These measurements do not have to be super accurate and it is nice to know that my Fluke can give me ambient temperature.
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I understood that you were confused initially. if you're still confused now, let's just say that some meters can display ambient temperature directly and some can display it indirectly. The preferred method is to use a thermocouple and read whatever it says on the screen.
Enjoy your meters.
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Some meters always display the cold junction temperature, whether a K-type thermocouple is connected or not. It is documented and is a feature.
In all meters, the measurement is taken close to the reference junction (ambient), with a thermistor, RTD, thermal diode or temp sensor IC.
Once the thermocouple is plugged in, that temperature is used for cold junction compensation.
The hot junction temperature can then be calculated, using voltage and look-up tables (or formulae) to compensate for non-linearity.
Shorting the probes, mimics a thermocouple with no induced voltage and the meter only displays the remaining cold junction temperature with its compensation (ambient).
Really?
My Fluke 287 show me 26,2C with short circuit leads and 24,7C with connected thermocouple to the end of this leads. So, what is reference and for what this reference, when type K thermocouple junction voltage well know and constant more or less for all thermocouple probes?
What reference temperature (in mV for processor) in digital thermometers that supported more than one types external thermocouples?
Have you even tried connected to your meter Type K thermocouples, already being some time under high or low temperatures to compare with DMM environment temperature?
IMHO, internal temperature that DDM show you with short circuit leads only for show user that temperature coefficient must be applied to the readings, when internal DDM temperature stabilized away from calibrated diapason 23+/-5C. It easy can be checked with just short circuit leads, no matter have you external thermocouple or not.
When you have external thermocouple, especially with fast response, internal and external temperature always will different with thermocouple connected and internal DDMs temperature can't be reference.
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'Built-in thermometer conveniently allows you to take temperature readings without having to carry a separate instrument'
The OP doesn't seem to know how temperature is measured with a multimeter.
Fluke wrote a confusing statement. One needs a separate instrument or tool called a thermocouple to measure the temperature of a DUT.
…which is included. The instructions tell you to use the thermocouple to take a measurement.
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We know that. It's not exactly built-in, is it?
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They should have said: The meter comes with a separate thermocouple probe which allows temperature measurements.
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Hi Wytnucls,
Could you explain please in details, for what we need 'could' junction measurement inside meter?
For meter both internal and external temperature unpredictable when it start measurement.
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Dave has done a video about thermocouple:
https://www.youtube.com/watch?v=AYblSfpKRUk (https://www.youtube.com/watch?v=AYblSfpKRUk)
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We know that. It's not exactly built-in, is it?
Do you have to carry around a separate thermometer device (http://www.fluke.com/fluke/r0en/electrical-testers/thermometers/fluke-50-series-ii.htm?PID=56085) to plug the thermocouple into? No, you don't. So yes, it's built in.
They should have said: The meter comes with a separate thermocouple probe which allows temperature measurements.
A thermocouple alone doesn't give you temperature readings. You still need the thermometer circuitry inside the meter.
This is Fluke's complete bullet on the features tab of the product page: "Built-in thermometer conveniently allows you to take temperature readings without having to carry a separate instrument"
Are you just being willfully dense for the sake of being argumentative? Seems to be a pastime on this damned forum... :palm: |O
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Spare us the insults please. You're the one that's dense. Fluke's writing is what confused the original poster.
Your thin interpretation of it doesn't make it true.
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Spare us the insults please. You're the one that's dense. Fluke's writing is what confused the original poster.
Your thin interpretation of it doesn't make it true.
Hardly. Everyone on the damned planet knows exactly what Fluke meant, except for you and the OP. Fluke's description makes perfectly clear what it does, since taking temperature readings necessarily requires some kind of probe. If it couldn't, they would have said "measures ambient temperature" so people wouldn't sue them for false advertising when they discovered that's all it could do.
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Spare us the insults please. You're the one that's dense. Fluke's writing is what confused the original poster.
Your thin interpretation of it doesn't make it true.
P.S. Asking if you're being "willfully dense" isn't an insult, it's an accusation of an action. An accusation I wholeheartedly stand behind. I don't suffer fools, or in this case trolls, gladly.
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This conversation is going nowhere, if you can't see how someone unfamiliar with thermocouples could be misled by what's written on the box, as reported by the OP.
Anyway, I have more important things to worry about. Have a good day.
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This conversation is going nowhere, if you can't see how someone unfamiliar with thermocouples could be misled by what's written on the box, as reported by the OP.
Anyway, I have more important things to worry about. Have a good day.
The OP seemed to be saying that he thought some 87V's had a thermometer, while other 87V's didn't. This misconception could easily have been cleared up - "all 87V's have them" - if only people hadn't started talking about the cold-junction compensation, which is largely an implementation detail of no interest to the user.
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SEE?! SEE?!! Now you guys know why I was confused!!!
Fluke's literature said that my multimeter has a "built-in" thermometer yet when I when I switched to the temperature range position I did not get a temperature reading (like I do on another brand of multimeter)! That's when I got to wondering if Fluke upgraded this feature in their newest version of that model. (Kind of like how car manufacturer's change things from year to year without renaming the car model.)
To make matters worse, Fluke's online 87V manual does not explain how to short the leads to get a temperature reading. My used multimeter did not come with a K-thermocouple.
Yesterday I wrote Fluke support and asked them to clarify this in the next version of their 87V user's guide. We shall see what happens.
Thanks again for a good discussion!
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Hi, Axtman,
For my Fluke 287(280) series, in user manual mentioned:
The primary display normally shows temperature or the message
“Open Thermocouple”. The open thermocouple message may be
due to a broken (open) probe or because no probe is installed
into the input jacks of the Meter. Shorting the V terminal to
the COM terminal will display the temperature at the Meter
terminals.
In your and my meter no any Look Up table of course. I read carefully Calibration manual for my meter and no any steps must be performed for temperature calibration during all process. Only DC mV calibration (step 1-6). All Fluke DDMs support only K-Type thermocouple and during measuring temperature just doing mV measuring at the end of thermocouple leads and make some simple calculation for show you temperature reading on display.
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Here is the response that I received today from Fluke.
***************
Hi David,
Sorry for the delay. I have been out of country on business.
You are correct that when we put the 87V in temp mode it reads OL. The meter itself does not have an internal temperature measurement. You are required to use the temp probe with it.
I will get the web site corrected as it is incorrect.
As for using the test leads, it is possible to get a general measurement, but it would not be accurate. I used a 53-2, 233, and 87V to experiment with. The 53-2 and 233 used the K-type thermocouple supplied with the units and I used the test leads for the 87V.
The 53-2 and 233 read within .5 degree, while the 87V was 4 degrees off. Obviously this was done in a somewhat controlled situation with the meters, test leads, and probes acclimated to the office temperature. Any of the Fluke meters that offer temperature have the algorithm built in for K-type thermocouples.
Thanks,
Sean
Sean Silvey | Product Specialist | FLUKE CORPORATION
email: sean.silvey@fluke.com | direct: 425.446.6992 |cell: 425.740.4294
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Who is the willfully dense clown now? ::)
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FWiW, a long time back I had 6 meters on the bench, including Fluke 87V, 289, 189, 233, and APPA 99111 and Mastech style 5208.
I wanted to compare their temperature capabilities and let them sit for about 2 hours to get their internals and externals to room temperature
Switched them on, put them in temperature mode and shorted their standard probes to see if they all read similar ambient temperature
They more or less were identical, give or take a fluctuating digit here and there.
Same deal when plugging in the exact same thermocouple probe on each meter, the probe placed in a pot of constant boiling water,
same readings, give or take a fluctuating digit here and there.
The results from the tests were good enough for my uses,
all the meters did a good job of measuring both shorted leads ambient and thermocouple probe tip temperatures
..and the curiosity stopped there :)
BTW, my Fluke 87V shows 'OL' if in temperature mode with no leads or thermocouple plugged in.
After a minute the meter displays 'LOL' to let me know there is no action happening unless I plug in a thermocouple ::)
After 10 minutes it displays 'WTF' and after a minute more, goes into sleep mode :=\
;D
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That 87V temperature display behavior seems silly. There must(?) be an internal temperature sensor if it's going to correctly calculate the cold reference value. Is this just a firmware shortcoming?
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If it's been in a cold or hot tool bag etc, I would assume the readings will be so so till the meter stabilizes to room temp, for reliable room/meter ambient temp readings by shorting the leads
I might have a play with it later and see how it goes against another model Fluke
Edit: Pulled out the 87V, 189 and an APPA 99111 in their cases from different locations,
no warm ups or stability time,
turned on, set to temperature,
shorted probes on all 3 meters,
all read the same ambient temp, give or take a .digit etc.