Joined: 2 September 2008
Location: US
Posts: 1

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Hi, I am using the 90614 in SMBUS mode, and i am not seeing the dynamic range of the device that i need to see.The Tobj values look correct for objects such as when i put my hand in front of the window it will register 85F and the Ta looks correct at around 78F. But when i put a soldering iron(approx 500F) within 2 inches of the window, the Tobj value is only reading around 135F. I have tried varying the Emissivity value in the register from .1 to 1.0 to see if it changes, but it only varies slightly around 5-10F. Is there any other register value i can change to increase the dynamic range?

Joined: 7 December 2005
Location: BE
Posts: 77

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Hi Gill,

From your measurements I calculate an emissivity of only 4-5%.
Metals have low emissivity. so a soldering iron is not really a good test object, but is too low.
What type of MLX90614 sensor are you using? I expect you are using a wide angle sensor -AAA or -BAA and that the soldering iron fills only a small part of the field of view of the sensor. So it mainly still measures the room temperature.

Do the values increase when you have the iron closer to the sensor? (This will not give good results as you are also heating the sensor directly).

Could you send me some hex data of the Ta and To you measure?

Kind regards,

Luc Buydens