IR temp reading

[FFMan]

I've been asked to look into developing a small project that could read and display the temperatures of two industrial rubber belts/bands running in a variable gearbox.

Does anyone have any suggestions as to how to read the temperature without contact, rather like those point and read type guns you can buy. What sensors do these use ?

thanks

[dkinzer]

Does anyone have any suggestions as to how to read the temperature without contact, rather like those point and read type guns you can buy.

See Tom Becker's post on using a non-contact IR thermometer:
http://www.zbasic.net/forum/about1250.html

[GTBecker]

Thermopiles are one solution.

http://www.melexis.com/Sensor_ICs_Infra ... IC_19.aspx

http://www.zbasic.net/forum/about1250.html

Tom

[FFMan]

thanks for the replies.

Thermopiles seem the answer, and due to the harsh environment expected something like this

http://uk.rs-online.com/web/search/sear ... um=0553333

would be appropriate. However I am not familiar with the 4-20ma interface - how would one interface this to a 328n ?

[dkinzer]

I am not familiar with the 4-20ma interface - how would one interface this to a 328n ?

You would typically use a current-to-voltage converter (aka a resistor) and then read the voltage using an ADC.

[spamiam]

The datasheet is not specific as to a typical circuit. No particular supply voltage nor resistance is mentioned.

Therefore I presume the exact values are not super critical. So, for a 5v supply, and if you want to limit current to 20mA max then you would need to use a 250 ohm resistor. You would measure the voltage from the positive side of the resistor with the other side going directly to ground. You would measure a range of 1.25v to 5v.

Addendum

the datasheet does specify a min sensor voltage of 6v and a max loop impedance of 900ohms. You could still use a 250 ohm resistor the way I indicated above even with the 6 volt supply. I would recommend using a resistor and clamping diodes on the input to the ZX

-Tony