SCXI Troubleshooting Resource
SCXI Frequently Asked Questions
Make sure that the signal reference settings for your DAQ device match the SCXI module. For example, if your device is configured for NRSE, make sure that your SCXI module is also (this may require a jumper setting).
Make sure that your signal is properly connected to an SCXI-13XX terminal block. MIO devices do not require connection to an SCXI-13XX.
There are two types of CJC sensors, the thermistor and the IC sensor. The CJC sensors are needed to adjust thermocouple measurements in order to give accurate temperature readings. The two different types of sensors work in different ways so it is necessary to know what type of CJC sensor is on your terminal block. A list of the terminal blocks and their respective CJC sensors is provided for you.
To communicate with multiple chassis, the communication path from the computer to the SCXI chassis must also be RS-485, via either an installed RS-485 communications card or an RS-232/RS-485 converter. Each chassis must have a unique address. Make sure the RS-485 network is configured for 4-wire operation. You must also be using NI-DAQ for PC version 4.9.0 or later.
Users sometimes set the "Connected to" field to a board for a module that is not directly connected to the DAQ board. Make sure that you set the "Connected to" field to None for all modules except the module that you have cabled directly to the DAQ board.
You need LabVIEW 3.0.1 or higher. This version of LabVIEW corresponds to NI-DAQ for PC compatibles version 4.5.0 and NI-DAQ for Macintosh version 4.6.6.
Use the onboard channel number to address a particular analog channel. Do not use the SCXI string ob0!sc1!md....
If you have enabled the 4 Hz or 10 kHz filter on the SCXI-1100, or if you are using high gains, set the channel rate (interchannel delay) to a value that gives the amplifier time to settle for each channel. The default channel rate is automatically set to the fastest rate with which the DAQ board can work, but no faster than 7 ms if you are using SCXI. You can use the AI Config VI to specify a longer interchannel delay, or you can use the advanced Analog Input Clock Config VI to specify slower channel clock parameters. Do not confuse the scan rate parameter, which determines the time between successive scans, with the channel rate. You can specify the scan rate, but not the channel rate, for the Easy I/O VIs and most of the Data Acquisition example VIs. However, you can specify the interchannel delay for the SCXI Thermocouple example VI.
The information in "Connected to" informs your software which SCXI module is physically cabled to the DAQ board. Therefore, if you have two SCXI modules and only one DAQ board in your system, only one SCXI module should have a DAQ board appear in this window. This value should be None for all other SCXI modules. The "Operating Mode" determines the type of communication path between the module and the board. Multiplexed mode corresponds to serial communication. Analog modules can only run in multiplexed mode and digital modules can run in either multiplexed or parallel mode. You must cable a module configured for parallel mode directly to a digital DAQ device. In parallel mode, you can use only one module per digital DAQ device; you must connect any other modules in the chassis, in either parallel or serial mode, to a different DAQ device. The only exception to this rule is the DIO-96/PnP, which can work with two digital modules in parallel mode or one module in parallel mode and any number in serial. The only DAQ device which works with modules in parallel mode is the MIO-16D.
You may have blown a fuse. There are two fuses located behind the fan in the SCXI chassis. Remove the fan by removing the four screws that secure it to the chassis and check to see if any of the fuses have blown. Consult the SCXI Chassis User Manual for more information on your fuses.
Most thermocouples are floating signal sources with low common-mode voltage; they require a path for bias currents from the SCXI-1100 amplifier to ground. Check jumper W1 on your SCXI-1100 module to make sure the jumper is in the factory-default position. Make sure that you have grounded the negative lead of each floating thermocouple and that your grounded thermocouples do not have high common-mode voltages. Also remember to average your temperature readings.
You may have a settling problem caused by either filters or high gains. First, check to see if you have enabled filtering. If you use a 4 Hz or 10 kHz filter on the SCXI-1100, you must scan channels at a slower rate. Because the filter circuitry is located after the amplifier, you must give the amplifier time to settle before switching to the next channel. If you are not using the filter, check the amplifier gains you are using on the SCXI-1100 module and the DAQ board. Using a very high gain on your SCXI-1100 module and on some DAQ boards also has the effect of increasing your settling time. Decreasing your scan rate (increasing the delay between channels) should solve this problem.
You can use any MIO board to accomplish this. Assume you need to set the gain for the first eight channels on the module to 100 and the gain for the last 24 channels to 1,000. Set the SCXI module gain to the lowest required gain and create multiple entries in the MIO board scan list that use different MIO board gains so that the total gain on each channel will be the desired gain. For this example, set the SCXI module gain to 100, and set the MIO board gain to 1 for the first eight channels and 10 for the last 24 channels. In NI-DAQ for PC compatibles and NI-DAQ for Macintosh, use the function call SCXI_Set_Gain to set the SCXI-1100 gain to 100. Then call the function SCXI_MuxCtr_Setup (deviceNumber, 1, 1, 8); this specifies that eight SCXI module channels are scanned for each entry in the MIO board scan list. The MIO board channel list is {0, 0, 0, 0} (remember that in multiplexed mode only MIO board channel 0 is used), and the MIO board gain list is {1, 10, 10, 10}. The first eight channels on the module will have a total gain of 100 * 1 = 100, and the last 24 channels will have a total gain of 100 * 10 = 1,000. Notice that you are now using four MIO board scan list entries instead of just one. For more complicated gain distributions, your MIO board scan list will be longer. The AT-MIO-16, MC-MIO-16, NB-MIO-16, and NB-MIO-16X can have up to 16 scan list entries. The AT-MIO-16F-5, AT-MIO-16X, and AT-MIO-64F-5 can have up to 512 scan list entries. In LabVIEW, use the channel list strings and input limits arrays to specify your gain distribution. You do not need to set the SCXI-1100 gain in the configuration utility; the Analog Input VIs determine the best module gain and MIO board gains for you based on your input limits. Put two entries in the channel list array– OB0 ! SC1 ! MD1 ! CH0:7, and OB0 ! SC1 ! MD1 ! CH8:31. Put two entries in your input limits cluster array. Set the first element limits to {-0.1 to 0.1} and the second element limits to {-0.01 to 0.01}. Using the OB0 specifier in your channel strings causes the Analog Input Hardware Config VI to modify the onboard MIO board gains as well as the SCXI module gain. The group channel settings array that the Analog Input Hardware Config VI returns shows the input limits and total gain for each channel, so you can verify your gain distribution. If your gain distribution results in an MIO board scan list that is too long for your MIO board, the Analog Input Hardware Config VI returns the -100370 error code (badScanListError).
Connect one of the SCXI-1140s to your DAQ board to ensure that the track-and-hold signal from a counter on your DAQ board has a path to the SCXI digital backplane. Other SCXI-1140 modules can read this information from the backplane. In this situation, all the modules operate in multiplexed mode.
These boards can scan multiplexing SCXI modules only under software control. The Lab-NB, Lab-LC, and Lab-PC boards must individually address and read from each SCXI channel. These boards do not generate the SCANCLK clock signal that is required for high-speed hardware scanning of multiplexing modules. However, the Lab-NB, Lab-LC, or Lab-PC can scan a single SCXI-1120 or SCXI-1121 module in parallel mode. The SCXI-1100 and SCXI-1102 do not work in parallel mode. The Lab-PC+ and any MIO board can scan any module in any operating mode.
Nothing, usually. The extra male connector on a cable assembly is called the breakout connector. You can use the breakout connector, in conjunction with the SCXI-1180, SCXI-1181, or SCXI-1351, to access unused DAQ board signals.
The SCXI-1162 and SCXI-1163 send digital data to the SCXIbus. However, the analog modules, by default, do not send digital data from the SCXIbus to the DAQ board. If you have digital and analog SCXI modules in the same chassis and control them all through a DAQ board cabled to an analog module, you must configure that analog module to send digital data out. You may not have been aware of these digital lines because you do not need to set them for the analog modules to operate properly. Each SCXI module user manual explains how to configure the module, with two jumpers, to send serial data out. One jumper connects the SCXIbus MISO line to SERDATOUT; the other jumper connects a pullup resistor to the MISO line.
One thing to try is to delete the configuration file (DAQCONF.CFG or
NI-DAQ Configuration Utility) and run your configuration utility
again.
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