Reading a thermocoup​le with the SCXI 1520

Does the SCXI 1520 have something to account for the interface connection heat, and is it needed? I've heard this is what the thermocouple modules do, and it is necessary.

The SCXI-1520 uses the SCXI-1314 Module which does not have cold-junction(CJ)compensation capability - meaning it can not compensate for either the temperature of the connection to the DAQ system, nor, the additional voltage effect due to the dis-similar metal contacts of the DAQ system. This correction is absolutly necessary for accurate temperature measurement. I suggest you use a "third-party" cold junction module from a vendor such as OMEGA Engineering ( The CJ sensors are battery powered and reference the signal to 32 Deg F while at the same time providing standard copper leads for the DAQ system.

Similar Messages

  • I Am Getting Inaccurate Readings When Some Channels of the SCXI-1520/SCXI-1314 Are Open Circuits

     Am Getting Inaccurate Readings When Some Channels of the SCXI-1520/SCXI-1314 Are Open Circuits
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    Surender Kumar

    No, DAQmx is superior and I strongly recommend you used DAQmx
    Elijah, I guess I understood the problem that Sunder is facing, coz even I had experienced it 2 years back
    What happens is if you scan only the channels to which sensors/strain gauges are connected, all is fine and you get good strain readings.
    But if you happen to include an unconnected channel into the scan list, all the subsequent channels after the open channel will show saturated readings.
    Right, Surender??
    The problem we found, lies in the settling time of the E series DAQ card's ADC. Even we were using PXI 6071 E
    Once the ADC saturates on reading an open channel, it cannot settle fast enough to read the next channel.Hence, the next channel also reads saturated value, instead of the correct value.
    This is irrespective of the sampling rate because, this happened even when we did continuous sampling at low scan rates of 10 to 100 samples /sec
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    We use the SCXI-1520 signal conditioner to test and calibrate bridge sensors that we manufacture and it works great.  While the system is not used (i.e. when the operator connectes a sensor to the system) the SCXI-1520 is automatically isolated by using relays in a switching system.  The primary intent for this is to avoid possibly damaging the signal conditioner.  (Operators do regretful things.)   This means that the excitation power is floating with no load while the signal conditioner is disconnected,.  I was wondering if it would be appropriate to have the system automatically apply a load resistor to the excitation source to keep it "warmed up" so to speak.  Most sensors are a 350 ohm bridge and may be as high as 5000 ohms.  I was thinking of applying a common 330 ohm 1/2 watt resistor as a load.  (We are currently only using two channels at a time.)  Although I'm sure it would not make things worse, I just wonder if it's worth the bother.  Please advise...

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    You can find the user manual for anything at  The manual for the SCXI-1520 is currently here.
    If you're programming in LabVIEW, you can find example programs for this device in the Example Finder.  (Click Help » Find Examples to open it.)  I recommending filtering by your hardware.  To do so, click the Hardware list in the bottom-left of the window and select "Add device".  After adding the SCXI-1520, select it from the list and check the Limit results to hardware box.  This will filter our examples down to the ones that work with your device.  They'll probably all be in the "Hardware Input and Output » Analog Measurements » Strain" folder.
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    I have an SCXI-1001 chassis and will soon be purchasing an accelerometer input module (SCXI-1531).  I'm also investigating possible accelerometers to buy.  Does anyone know if the the Analog Instruments ADXL330 accelerometer can be made to work with the SCXI-1531?  Here is a link to the Analog Instrument's page about the device:

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  • What is the combined effect of the SCXI-1520 Gain and NI-Max Gain?

    LabVIEW 6.1
    Windows 2000
    I'm trying to determine how the gain that is settable on a given channel of an SCXI-1520 module is combined with the gain that NI Max assigns to a Virtual Channel.
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    Hello Steve,
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    When you set the input signal ranges in MAX for your virtual channel, SCXI and DAQ board gains are applied. For example, if you create a voltage channel to read the mV output of a sensor, and set the range to +/- 10mV, the SCXI Module would apply a gain of 1000 to the signal and send the resulting +/-10V to the MIO DAQ device. The DAQ device will then attenuate this signal to +/-5V (the range of the ADC) by applying a gain of 0.5. Now, if you set the input signal range to +/-1mV, the SCXI Module will apply its maximum gain of 1000 and send the resulting +/-1V to the MIO device. The DAQ device will then amplify this signal to +/-5V by applying a gain of 5.
    If you are still seeing a residual offset after null calibration, you should use the Auto Zero property. This property measures ground before an acquisition and then subtracts that value from every subsequent measurement. You can set this in a strain task, or with a Channel Property Node in LabVIEW.
    Let me know if you have any further questions.
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