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TMP117: Applications question about TMP117 sensors

Jennifer Goodell
Prodigy 10 points
Part Number: TMP117
Other Parts Discussed in Thread: LMT01,

Hi there,

I want to make sure that the TMP117 is the appropriate solution to our engineering problem. It has an acceptable working range and accuracy. However, in our application we will be measuring the temperatures of several items inside a thermal chamber.

Will long lead lines add measurement error to the system?

Since the TMP117 requires a micro-controller, is there one that is recommended for robust operation?

Will we be able to connect up to 30 sensors on the same 2 wire bus?  If so, will that affect the resistors we attach to the system?  

It appears that the available packages are designed for board mounting; is there another package that could be used without a board so that it can be in direct contact with the item under test?  

Can these ICs interface with LabVIEW software? 

If the TMP117 isn't right for our application, can you recommend an IC that might be?  Temp range: -50 to 90C.  Desired accuracy > 0.25 degC. 

Thanks,

J

  • 0
    TI__Mastermind 35915 points

    Hi J,

    TMP117 is a digital device, so the length of wires can't alter the temperature data transmitted like an analog signal would.

    Any MCU with I2C support is suitable. 

    Every device on the I2C bus must have a unique address. TMP117 can only be configured for 4 different addresses using its ADD0 pin. See Table 7-2 in the datasheet. You would need 8 separate I2C buses to operate 30 TMP117s. Here are some TI MCU that have at least 8 I2C buses built-in: https://www.ti.com/microcontrollers-mcus-processors/microcontrollers/arm-based-microcontrollers/products.html#p299=8;10

    If you're asking about the I2C pull-up resistors connected to SCL and SDA, the TMP117 is specified for 3mA on its SDA pin. This means the minimum pull-up resistor is Supply Voltage divided by 3mA. Generally, the pull-up resistors must be reduced to compensate for parasitic capacitance of long wire runs or additional I2C devices on the bus.

    TMP117 is only offered in surface mount packages. Here is a list of TI temperature sensors in through-hole packages: https://www.ti.com/sensors/temperature-sensors/products.html#p2954=TO;TO-92 These are all analog output, except for LMT01, which has a pulse count output. 

    Any TI temperature sensor could be interfaced with LabVIEW software, but you will have to develop the bridge from our IC output to PC software. We sell ICs not test equipment. Our EVMs, such as TMP117EVM, have a USB-to-I2C bridge as part of their hardware, but we do not support LabVIEW connectivity.

    Here is a list of TI temperature sensors which meet your temperature requirement: https://www.ti.com/sensors/temperature-sensors/products.html#p2033max=0.1;0.25

    thanks,

    ren