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TC-08 Calibration method

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TC-08 Calibration method

Postby mperman » Fri Feb 08, 2013 9:41 am

I need to get our TC-08's UKAS calbrated for safety approval testing. The test house is offering two methods, one uses thermocouples and the other is with injected signals.
Do you know if there are any pitfalls with the injected method - which method does PICO use?
Many thanks
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Re: TC-08 Calibration method

Postby Martyn » Mon Feb 11, 2013 7:40 am

We use reference signals, not thermocouples.
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Re: TC-08 Calibration method

Postby mperman » Tue Feb 12, 2013 8:15 am

Martyn wrote:We use reference signals, not thermocouples.

Thanks Martyn.
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Re: TC-08 Calibration method

Postby Yukinobu Arata » Mon Jun 11, 2018 8:19 am

I have logged temperature using TC08. Recently, I got concerned with how the temperature is precise. Then I have arrived at this post. My question is
1) Do we need to somehow calibrate temperature based on some reference temperature before every measurement of TC-08?
2) If unnecessary, how the precision of measured temperature is guaranteed?
3) Could you explain about "reference signals" for the calibration in detail? What could generate reference signals? 4) The given reference temperature from the "reference signals" is used to adjust temperature shown on TC-08?

I am sorry if I would embarrassed people familiar to TC-08, but these inquiries are critical to me.
I'd appreciate if anyone would give me some support to follow up your information exchange?

Best

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Re: TC-08 Calibration method

Postby Gerry » Tue Jun 12, 2018 1:23 pm

Hi Yukinobu

First of all, just so that we're clear, the objective of Calibration is to use a sufficiently more accurate measurement instrument to determine the accuracy of the instrument being calibrated. This is so that you can establish if the instrument being calibrated can perform a measurement within the range of accuracy specified by the manufacturer, and if not take steps to bring the instrument back to within the specified operating range. In order to be sufficiently more accurate, the measurement instrument used for calibration needs to have an accuracy at least 3 times (preferably 10 times) greater than the device being calibrated, and needs to have been calibrated itself, by a sufficiently more accurate measurement instrument. This requirement for the calibration instrument to be calibrated must be traceable right back to a National or International Standard (i.e. to the instrument used to define the standard at the National or International level).
Note that calibration doesn't determine the precision of the measurement instrument, just the accuracy. Also, in a large proportion of measurement applications the absolute temperature is not as important as the difference between 2 temperatures, so precision is quite often more important than accuracy (and doesn't require calibration).

To answer your questions:

The highest guarantee (highest level of confidence) you can have that your TC-08 is still accurate, would be to calibrate it before every measurement, but what you need to ask yourself is "Is this level of confidence really necessary?". At Pico Technology we have Vector Network Analyzers within our RF product range that are operating within frequencies where the wavelengths are comparable to the interconnections, and so even differences between cable lengths (among other factors) have a big impact on accuracy, and must be calibrated out before each measurement. Variation due to drift in our data loggers is a very gradual process, and we have a relatively large margin of uncertainty around our specification of accuracy, while our TC-08 data loggers leave the factory well within that uncertainty range (which is also true of recently re-calibrated TC-08's). So, this means that the level of confidence that our TC-08 data loggers are within our stated accuracy specification, is extremely high, and they will in general retain their accuracy for a relatively long time.
The problem with the question of "When to calibrate?" is that the amount of time that the instrument will remain within the specified range of accuracy will vary depending upon how you use the measurement instrument (e.g. if you are taking measurements close to or far from the specified operating limits) how often and for how long you use it, and how you store the instrument when not in use (for example, low or high humidity). So, for typical usage and storage, we recommend that our products are calibrated once a year. However, when you use your TC-08, if you are going to be pushing limits, using it more than normal, or store it in unfavourable environments, then you will need to calibrate the instrument more often.

At Pico Technology when we perform a calibration we use Thermocouple simulators to calibrate the TC-08's (which will give the appropriate reference voltage for a required temperature reading), and we make the measurement within a temperature controlled environment. We consider a calibration failure to be a Product fault and will therefore make the necessary modifications to bring the instruments accuracy back to within the range that we specify.
If you want a calibration done then you just need to send us an email at support@picotech.com, mentioning the device, model number, and serial number, and with your full postal address. We can then give you a returns number for you to send the device back to us with, so that we can turn your calibration around within 5 working days of receiving it. All the reference instruments that we use for calibrations are traceable to UK national standards, and we have the instruments regularly calibrated at third party calibration houses.
Note that if you are buying a new measurement instrument, and want to receive a calibration certificate for it, you must specify this at the point of sale (in your email, phone call, or online shopping cart).

Regards,

Gerry
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