temperature sensor with usb-6009 daq

[ba7soun]

Greeting

i want to use a temperature sensor with usb-6009 to record the variation of a body temperature within about 15 min,then use the data in labview.

if you please can advise me with the best low-cost sensor to use and the way/circuit of connecting it to the usb-6009.

[dhruvchokshi]

Hi ba7soun,

Ideally, the USB 6009 is not an apt device to measure temprature becasue lack of signal conditioning typically required while using temperature sensors - such as cold junction compensation. You may explore using devices such as the NI 9211,  a C series module. 

If you still want to use USB 6009 for temperature measurement, you can go ahead and procure a thermocpuple (J-type, or other types). You can connect the thermocouple to one of the analog input channels on the USB 6009, and acquire the raw voltage. Next you will have to calibrate the raw voltage in terms of temperature (C or F) yourself through software. This will involve mathematical operations on the acquired voltage within software. 

Hope this helps. 

Regards,

Dhruv Chokshi

[dhruvchokshi]

hi ba7soun,

Actually, one shouldn't use USB 6009 for thermocouple measurements, since the DAQ device is not accurate enough to measure a a TC output signal which is in the range of 0-80mV.

In addition to exploring other DAQ devices such as NI 9211, you could also explore using a thermistor with external excitation, as your temperature sensor. 

Reagrds,

Dhruv Chokshi

[ba7soun]

thank you dhruvchokshi,

actually,  we are working at the university lab and the only device available at our university is the usb-6009.  our project needs a tempareture sensor  so am

searching fort the best option i can have. after googling i found some projects using the LM35 sensor(attachement)  but not sure about the result- as you said

about low output voltage.

so if there is a way that can lead to good results -by amplifying the output or.. and how?

[dhruvchokshi · Accepted solution]

Hi ba7soun,

Whether you can use LM35 with USB 6009 depends on the output voltage range of the sensor. I understand that it requries a 5V supply with respect to ground, which you can provide from the USB 6009 (more than 200mA should not be drawn from the USB 6009).

The maximum range of the USB 6009 is -10V to +10V, while the minimum range is -1V to +1V, so surely the output signal of the LM35 will be within this range. What you need to do is compare the full range of the output signal with the full range of the DAQ divided by 2exp(14) (because its a 14 bit ADC) and ensure that the former is much greater than the latter. 

Regards,

Dhruv Chokshi.

[LiuXuedong]

Hi Bahsoun：

Now i'm facing the same problem just like yours，maybe a little bit different：use NI 6009 to record and visualize the temperature data that sensor acquires，i'm quite curious about your final solution，it will be very helpful if you can offer me some advice.

Regards.

[ba7soun]

Hello LiuXuedong, 

Attached my full report in addition to the LabView files I used.

In Short, I managed to use the Temperature Sensor - LM35, it is an integrated circuit sensor that can be used to measure temperature with an electrical output proportional to the temperature (1mV/ ^oC).

• Why Use LM35s To Measure Temperature?

o You can measure temperature more accurately than a using a thermistor.
o The sensor circuitry is sealed and not subject to oxidation, etc.
o The LM35 generates a higher output voltage than thermocouples and may not require that the output voltage be amplified.
o The LM35 does not require any external calibration or trimming and maintains an accuracy of +/-0.4 oC at room temperature and +/- 0.8 oC over a range of 0 oC to +100oC.
o Another important characteristic of the LM35DZ is that it draws only 60 micro amps from its supply and possesses a low self-heating capability. The sensor self-heating causes less than 0.1 oC temperature rise in still air.

Then Introducing An Amplifier - The LM324:

• Why we need the LM324?

USB-6009 DAQ has voltage range accuracy between 1.53 mV and 7.73 mV. And as the sensor's Vout is in mV, it's very sensitive to be connected directly to the DAQ.
Hence, we introduced the LM324 amplifier to get a gain of 11 times the sensors Vout . Now, the amplified voltage isn't sensitive to be connected to the DAQ.

• Specifications of the LM324:

o Short Circuited Protected Outputs
o True Differential Input Stage
o Single Supply Operation: 3.0 V to 32 V
o Low Input Bias Currents: 100 nA Maximum (LM324A)
o Four Amplifiers Per Package
o Internally Compensated
o Common Mode Range Extends to Negative Supply
o Industry Standard Pinouts

Circuit Construction:

Required Materials:

• Temperature sensor LM35
• Amplifier LM324
• Resistors  10K –  100K
• LED

Circuit Diagram: (Attached)

LabView Diagram: (Attached)

[LiuXuedong]

Hello，Ba7soun：

Thank you for your information，it's very detailed and give me lots of inspirations.

My sincere greeting.

Liu.Xuedong

[ba7soun]

Happy to help, Cheers!