Test and Measurement Forum

I have two TC-08's and they are off by about 1.5-2 degrees in the 0 to 100 range. What address do I send them to for calibration. Do I need to include my serial cable?

Hi,

The TC-08's specification for accuracy is 0.3% of current reading plus 0.5 deg C. What it the instrument and its accuracy of the unit that you are to compare against the TC-08.

To arrange a unit to be calibrated please send an email to:

tech@picotech.com

Please specify in this unit the unit, what is required (calibration) and your contact details. Further detials will then be provided, with regards to cost, timescale and detivery address.

Best regards,

Be aware that this topic discusses the use of water near electricity and as such some care must be exercised in order not to risk electrocuting ones self!!!!

TAKE CARE - Water and electricity in close proximity are lethal !!!

That being said, before the days of cheap electronics, one of my first duties was the maintenance of temperature measuring systems. When one was in the field (in my case literaly) then checking a thermocouple and its associated systems could be a bit problematic.

However it's not too dificult to get a simple check!

Reference 0°C
Get some ice and crush it fairly fine (don't hurt yourself doing this, it can be tricky). Place the ice in an insulated container (perhaps a thermos flask) then mix about 50/50 with cold water, stir occasionaly and wait about 10 minutes. What you now have is a zero degree temperature reference (well as close as you will get and as near as you need for a TC08 or similar, infact these used to be used as the Cold Junction references for thermocouples). Pop your thermocouple into the middle of the mixture and you should have zero °C. No voltage offsets, inteference, earthloops etc.

Reference 100°C
For a 100°C reference, well nominally water boils at this temperature (sea level and air pressure adjustments are actually required) but I assume you are not up some mountain (or you would have checked the compensations!!!) and again it will be near enough. Don't forget that most domestic kettles don't like being repeatedly switched on, so I suggest great care and a pan, leave to boil for a good five minutes before your first measurement and don't forget to adjust the heat such that you aren't measuring the temperature of the heat source, so the water should be just simmering nicely.

If you want to see if you freezer is working then it should be -18°C (of course the position in the freezer is important as well, so expect +/-1°C and your fridge should be between 4°C and of course above 0°C.

And now you know why I have a fridge and a kettle (for checking equipment of course) !!!!!! They are also helpfull for making coffe and keeping my sandwhiches fresh of course as well!

One final comment........

I have been using these units (it would appear from thier earliest days) and I would be supprised if they were as inaccurate as you suggest.


Cheers and don't forget to fill in what you found.

I have been talking it over with some other people and they think there may have been a flaw with my inital setup when I did the first Ice Bath. The TC-08 was placed next to the laptop computer being used.

Is it possible that the heat from the computer fan was enough to affect the module? I just reran the ice bath temperature check and it worked fine at a distance from the PC.

But now I have one more problem. I have two data loggers and two laptops. Data logger 1 displays 0 degrees in the ice bath on one computer, but not the other. However, datalogger 2 works fine on both laptops. Any ideas how to find out what component is malfunctioning?

Inside the TC08 data logger is a temperature sensor which is responsible for temperature compensation. It is sometimes refered to as cold junction compensation.

I suspect from your comments that the fan from the computer could be heating the TC08 unit and in turn mean that the temperature of the 'cold junction' has not actually stabilised. Also one of the rules for using thermocouples says that 'the temperature of BOTH the junctions (the connectors two pins) must be the same' and you are implying that they are not. Under these conditions you will end up with all sorts of errors as the connections become....... thermocouples measuring thier own temperature. I have never let it happen because it's so important.

Alternatively of course you could also have a really nasty P.C. which is giving out some really horrible electromagnetic interference. Or have a mains cable too close.

The best advice at this point is; be very methodical, change one thing at once and carefully observe the effect.

Such is the fun one encounters as an instrumentation engineer.....


P.S. if ANYONE else has any ideas don't be shy, let us know...