Hi, Peranders
Could this help you?
http://www.google.be/search?hl=nl&ie=UTF-8&oe=UTF-8&q="thermocouple+made+of&meta=
/Hugo
Could this help you?
http://www.google.be/search?hl=nl&ie=UTF-8&oe=UTF-8&q="thermocouple+made+of&meta=
/Hugo
Peranders,
Good question - assuming you want a thermocouple emulator : -
You would need an accurate voltage, that corelates accurately with the Seebeck coefficient of the thermocouple you need to emulate.
This coefficient is non-linear, so you need to calibrate at each temp emulation setting.
Some thermocouple amps have DC present at their inputs and need the thermocouple DC resistance present to work, so the o/p impedance and a DC current path similar to that of a thermocouple needs to be present too.
The output should use a standard thermocouple plug / socket.
I've got one at work, I haven't been able to get it apart yet
Andy
Good question - assuming you want a thermocouple emulator : -
You would need an accurate voltage, that corelates accurately with the Seebeck coefficient of the thermocouple you need to emulate.
This coefficient is non-linear, so you need to calibrate at each temp emulation setting.
Some thermocouple amps have DC present at their inputs and need the thermocouple DC resistance present to work, so the o/p impedance and a DC current path similar to that of a thermocouple needs to be present too.
The output should use a standard thermocouple plug / socket.
I've got one at work, I haven't been able to get it apart yet
Andy
Hi Peranders,
The output of a thermocouple is nonlinear and the output voltages (<100mV) vary with different thermocouple types. Therefore a calibrator is not a simple matter. Here is a link to the Omega technical reference page. There is a wealth of information on all sorts of temperature measurement devices available here.
http://www.omega.com/temperature/Z/zsection.asp
Yes, you will need to assign a linearized temperature to a non-linear output from the thermocouple.
Yes, sort of, as you will need to have a lookup table each type of thermocouple. The table will provide the volt-to-degrees conversion values
Yes, each different bi-metal pair has a different output and V/T curve.
Hope this helps.
Rodd Yamashita
The output of a thermocouple is nonlinear and the output voltages (<100mV) vary with different thermocouple types. Therefore a calibrator is not a simple matter. Here is a link to the Omega technical reference page. There is a wealth of information on all sorts of temperature measurement devices available here.
http://www.omega.com/temperature/Z/zsection.asp
The direct answers to your questions are:peranders said:
Yes, you will need to assign a linearized temperature to a non-linear output from the thermocouple.
Yes, sort of, as you will need to have a lookup table each type of thermocouple. The table will provide the volt-to-degrees conversion values
Yes, each different bi-metal pair has a different output and V/T curve.
Hope this helps.
Rodd Yamashita
Hi Peranders,peranders said:
I'm not sure what a "thermocoupling amplifier" is. Hopefully, we are talking about the same thing.
The thing is that it’s not the thermocouple that gets calibrated, it’s the device or unit that reads the voltage the thermocouple is putting out as it varies with temperature. The thermocouple itself cannot be altered so there is no way to “calibrate” it.
There are two ways that thermocouple measuring devices are “calibrated” in the field or in the lab so there are two main type of calibrating devices. The first, as Andy alluded to, is the TC emulator or simulator. It is used in place of the thermocouple in question by emulating the voltage of various types of thermocouples at selected temperatures. An accurate voltage that represents the output of the thermocouple at a specified temperature is generated and input to the measuring unit. The measuring unit is then calibrated based on this simulated thermocouple. If you were to make one of these, you would have to have the voltage-to-temperature tables at hand and be able to generate the voltage that is equivalent to the thermocouples output at the selected temperature.
The second type of “calibrator” is really just an accurate measuring unit with an accurate temperature “reference” to correlate to. The “calibrator” will measure the voltage from the thermocouple which is in proximity to a reference temperature measuring device, convert that voltage to a number with temperature units, and compare that temperature to that of the reference. The reference can be a thermometer in an ice bath (zero degrees C), or it can be a measuring device of higher accuracy then the typical thermocouple such as an RTD (Resistive Temperature Device). Of course, the reference has to give you a reading of temperature. This type of device would be used to calibrate the TC simulators described above.
Rodd Yamashita
Thermocouple or Thermal Transfer
if you want to very acurately measure RMS voltages you use a thermal transfer standard -- avoids the pitfalls of electrical measurement -- thus if you want to acurately measure power you would use one of the very expensive fluke Thermal Transfer Standard's. here's a link to the NIST tutorial:<p> http://www.acdc.nist.gov/Tutorial.pdf
if you want to very acurately measure RMS voltages you use a thermal transfer standard -- avoids the pitfalls of electrical measurement -- thus if you want to acurately measure power you would use one of the very expensive fluke Thermal Transfer Standard's. here's a link to the NIST tutorial:<p> http://www.acdc.nist.gov/Tutorial.pdf
Re: Re: Re: Thermocouple calibrators - what's inside?
Is this what you're looking for?
For ~$100USD http://www.omega.com/ppt/pptsc_righ...k10&subsection=K10&book=Temperature&des=pptsc
Rodd Yamashita
Peranders,peranders said:
Is this what you're looking for?
For ~$100USD http://www.omega.com/ppt/pptsc_righ...k10&subsection=K10&book=Temperature&des=pptsc
Rodd Yamashita
My problem is: Is it worth manufacturing a cheaper calibrator than a 1 kUSD device? My costumer think it's too expensive but at the moment I have no idea how accurate "my" calibrator must be. Can I make it cheaper and good enough. It doesn't have to be at calibrator standard, so I gathered.
To answer your question: Maybe Thanks
To answer your question: Maybe
Thanks
Peranders,
My experience is in providing data acquisition and controls for dynamometer based testing systems. A common question from our less experienced customers is what quality/priced calibration equipment should they purchase for their in-house calibration activities. WRT, thermocouples, with their inherently poor accuracy (typically +/-0.5’C at best), it doesn’t make sense to spend too much money on TC calibrators. Rather, acceptable results can be had investing $500 or less on a calibrator/simulator that is capable simulating the outputs of 2 or more TC types as well as Platinum RTD’s while acting as a mV/mA source as well. Such electronic device are available from many sources here in the US as I would expect they are in Europe.
Both of these distributors offer TC simulators for <$500USD. There many others as well.
http://www.omega.com/toc_asp/subsectionSC_new.asp?ref=&Nav=&subsection=K10&book=Temperature
http://www.coleparmer.com/catalog/catalog_welcome.asp
Rodd Yamashita
My experience is in providing data acquisition and controls for dynamometer based testing systems. A common question from our less experienced customers is what quality/priced calibration equipment should they purchase for their in-house calibration activities. WRT, thermocouples, with their inherently poor accuracy (typically +/-0.5’C at best), it doesn’t make sense to spend too much money on TC calibrators. Rather, acceptable results can be had investing $500 or less on a calibrator/simulator that is capable simulating the outputs of 2 or more TC types as well as Platinum RTD’s while acting as a mV/mA source as well. Such electronic device are available from many sources here in the US as I would expect they are in Europe.
Both of these distributors offer TC simulators for <$500USD. There many others as well.
http://www.omega.com/toc_asp/subsectionSC_new.asp?ref=&Nav=&subsection=K10&book=Temperature
http://www.coleparmer.com/catalog/catalog_welcome.asp
Rodd Yamashita
Re: Re: Re: Thermocouple calibrators - what's inside?
I understand that an electronic method is easier. However, this is likely to be a tertiary or lower standard unless you are prepared to spend serious cash.
The Beckman system can be a secondary standard.
-------------------------peranders said:
I understand that an electronic method is easier. However, this is likely to be a tertiary or lower standard unless you are prepared to spend serious cash.
The Beckman system can be a secondary standard.
Peranders,
What type thermocouple amplifiers do you need to calibrate (e.g. K type)?
Once you have that answer what accuracy do you need, over what temp range?
The output of any thermocouple is defined by physical data freely available from the national standards organisations, and generating a voltage of suitable precision is not that difficult.
It's harder if you need to cover multiple thermocouple types, but I use a K-type calibrator, with about 5-6 temp settings (from -20 to +800) and it's a lot cheaper than the Fluke device.
I'll dig out details if interested.
Andy.
What type thermocouple amplifiers do you need to calibrate (e.g. K type)?
Once you have that answer what accuracy do you need, over what temp range?
The output of any thermocouple is defined by physical data freely available from the national standards organisations, and generating a voltage of suitable precision is not that difficult.
It's harder if you need to cover multiple thermocouple types, but I use a K-type calibrator, with about 5-6 temp settings (from -20 to +800) and it's a lot cheaper than the Fluke device.
I'll dig out details if interested.
Andy.
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