Hello:
I need to measure temperature changes in the air. I'm testing with the digital sensor LM73, but I do not know what is the maximum warp speed of change that I can sensing. I did not find data about the LM73 thermal response and its thermal mass, or how to measure them. Can you help me?
Hi,
Thermal response time is mainly controled by the package type, the die itself has some effect but as a first pass you can neglect it. The LM73 comes in a SOT23 package so you can really close to looking up a part that has all of the thermal response information for that particular package. I would recommend looking at the LM45 datasheet. It has some great curves I have included here:
This gets you close becuase you also need to take into account the pcb that you mount the device to and the traces or ground plane around the part. Also what temperature are you trying to measure air or pcb. Here's the layout we used for the LM45:
Also keep in mind that the LM73 is a digital sensor so it will report the temperature out based on the conversion time of the internal analog to digital converter. For the LM73 that depends on the programmed resolution and can range from 14ms to 112ms.
I hope this helps.
Take care,
