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Several Infrared thermistor temperature sensors & strain gauges

infrared temperature sensor strain gauges thermocouple

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#1 LancerMotorsport

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Posted 11 December 2013 - 09:32 PM

I had initially wanted to connect several thermistor based infrared temperature sensors along with strain gauges, the ideal number was 6 of each or 12 of the same type of sensor at once.


I intend to power them using the 5V power output on the labjack but am concerned by the amount of current that will be supplied. USB 2.0 ports usually run at about 500mA. Is that enough current supply to run that many sensors? If so, what is the maximum amount of these types of sensors I could run at once by only using the current via the USB?



#2 LabJack Support

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Posted 12 December 2013 - 10:37 AM

For the temp sensors, please post a link to details so we can check them out.  Here is our general app note about temperature sensors if you did not see it:




For strain gages, you need to provide a bridge.  If you have a single 350 ohm strain gage, you will use 350 ohm resistances to complete the bridge and thus the overall resistance of the bridge will be 350 ohms.  That means if you excite bridge with 5V, each bridge needs about 14mA, so 6 bridges need about 84 mA which is no problem for the VS supply on the U6.


Note that bridge circuits provide a differential signal, so if you are measuring the raw bridge signal with the U6 each will use 2 analog inputs.  If you need more than 14 analog inputs you will want to add the Mux80 to the U6.



#3 LabJack Support

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Posted 12 December 2013 - 10:38 AM

Also, how fast do you want to acquire the inputs?

#4 LancerMotorsport

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Posted 12 December 2013 - 10:51 AM

The infrared temperature sensor I planned on using is the following:




It is a thermopile/thermistor based sensor so I assumed I would also need a bridge to utilize it. I chose this because it was one of the few IR sensors to output an analog reading, as I have not worked with digital or I^2C outputs before I wanted to stay with something I was comfortable with.


My purpose was to collect tire temperature data on a SAE formula car and wanted to catch the temperature rise going around corners, ideally I wanted to have the sensors running at 25Hz

#5 LabJack Support

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Posted 12 December 2013 - 05:31 PM

It looks like your temperature sensor has 2 sensors:


    - A thermopile for non-contact sensing.  Looks like it is similar to a thermocouple, but the response is a little higher ... roughly 100uV/degC.  This does not use any power, but rather it actually generates power.


    - A thermistor to measure the temperature of the sensor itself.  This is for CJC (cold junction compensation).  Not sure if you need to use this, or can just use the temperature of the U6.


If you are not familiar with thermocouples, start here:



Also tagged with one or more of these keywords: infrared temperature sensor, strain gauges, thermocouple

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