Post by Lake Shore Ryan on Mar 27, 2017 23:39:23 GMT -5
Hi Julius,
Sorry for the delayed response, I wanted to get more familiar with how this scenario would play out on our instruments and software.
Firstly, the equation is more like:
Temperature = f(Ureading)
where Ureading = Umeasured - Uoffset
and Uoffset = Umeasured @ calibration temperature - Uof curve value @ calibration temperature
Uoffset will be fixed for as long as you use that calibration. So it is most valuable when you are most interested in accuracy over a narrow temperature range.
If you are interested in a large temperature range like you are, the generated voltage from the thermocouple from 300 to 1000 K could vary greatly from 1 to 30 mV respectively for a K type thermocouple. So calibrating an offset at a single point would give a poor result.
Instead use Curve Handler version 8.3 or higher and use the Make Adjustment To Curve File option to create a more gradual adjustment to the curve like I showed in the previous post. Since you have such a wide temperature range, I'd suggest adjusting the curve with multiple points (if you have access to a more accurate thermometer than a thermocouple) by clicking the Next Point button to add additional points.
I'm not sure if you're considering it, but I couldn't recommend our thermocouple wire for your application which has plastic insulation due to our focus on cryogenic applications. Instead, I'd suggest searching for ceramic beaded thermocouple wire (if you haven't already).
If you can find an appropriate type K thermocouple, you could use the inbuilt temperature curve in the 335 for this thermocouple type and apply adjustments as I mentioned above.
When working with thermocouple though, you should know that thermocouples are notorious for not being very repeatable over multiple thermal cycles. So you may need to recalibrate your thermocouple regularly if you are concerned about temperature accuracy. The 335 can be capable of handling whatever level of accuracy you require. However, the thermocouple itself will probably be the greatest source of error in your measurement. They are difficult sensors to use accurately, which is the reason they aren't the preferred sensor to use unless they're the only sensor capable of surviving the measurement temperature.
I hope this helps.