SCXI-1120 Gain

I have 5 test racks running the same hardware and software. On one rack, an SCXI-1120 board seems to have a gain of 2 on channel one no matter what I do. The other 7 channels have unity gain. The input on channel 1 saturates at 4.12 volts. The inputs on the other 7 channels saturates at 8.24 volts. I've tried 3 different boards in the rack and the problem persist. The boards work fine in other systems with identical software and configuration. I've reinstalled traditional NI-DAC. I've set the gain using both MAX and AI config.vi. I've also tried installing the board in a different slot. Any ideas?
MS Windows XP
LabVIEW 8.2
Traditional NI-DAQ ver 7.4.1
SCXI-1001 chassis

shall,
If I understand properly, the problem is following that particular slot in the chassis, not the board that was in the slot. So these boards when placed in other slots all have gain of 1? Would it be possible to put the 1120 in a different slot of the SCXI and place some other board in the malfunctioning slot to work around the problem. I have found no known issues with the 1120 and gain.
Also, it might be worth while to check all the jumpers on the boards againt the user manual to make sure they are in the proper locations.
-Marshall R
National Instruments
Applications Engineer
One stop for all your NI-VISA Support
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Similar Messages

SCXI-1120 temperature limited to 106 C

I'm using a SCXI-1120 with a 1320 and the PCI-6031E. The TC is type J. The MAX is set at 2000 gain along with the 1120 module. I'm back to using the 1120 Thermocouple VI from LabVIEW ver 6.1. A test box was made to input mV into the 1320 while monitoring it on a Fluke 52II Thermometer to verify calibration. The chart reads accurately up to 106C where it flat-lines. I need to measure a range of 20 to 500C. What have I overlooked here?
wAllenr
Attachments:
LabVIEW_Temperature_Sample.pdf ‏64 KB

Found the answer, I was multiplying gain not dividing.

Can I measure frequency with a SCXI-1120 module and SCXI-1320 terminal block?

I am attempting to measure a square wave from a directional encoder to display RPM of a dynamometer. The waveform will have a frequency of 0-4KHz, with 3.6KHz being nominal, at about 5volts RMS. How can I measure the frequency of this waveform with the hardware I am currently using? In addition to what is listed above, I am using a PCI6034E GPIB card and LabView software.

In order to measure frequency, I would not recommend to use the SCXI-1120, but the SCXI 1126, which is a programmable isolated F-to-V module.
If by any reason you do not want to use SCXI-1126, then I would suggest to use the counter/timers of your board. The counter/timers are TTL compatible, and are the devices that we mostly recommend for doing precise frequency measurements.
In order to have access to the counter/timers of your board through your SCXI chassis, you will need SCXI-1180, which is basically a feedtrhough panel for your DAQ board.
Once we have access to the counter/timers through the SCXI chassis, we can proceed with the coding.
I found a pretty good webpage that clearly explains how to perform frequency measurement with the DAQ-S
TC counter/timers (DAQ-STC is the type of counter/timer chip that you DAQ device has). Here is the link to it:
Pulse Width & Frequency Measurements
As you will see, this link contains tutorials, application notes and example programs. I would recommend to pay special attention to the example program called: DAQ-STC: Measuring frequency.
Good luck with your application!

During continuous scanning thermocouples with a SCXI 1120 module is the cjc reference read each scan?

Did the developers of the DAQmx drivers improve the temperature scan capability of the SXCI 1120 module over the methods used in the traditional drivers?
When using the SCXI 1120 module for temperature measurement and in the continuous scan mode with traditional drivers the cold junction reference was only checked on the initial start of the scan. In order to maintain accuracy it was necessary to restart the scan.
For the most part I have switched to the 1125 module for thermocouple measurement but I need to use some 1120 modules on a test stand now and I will be using the DAQmx drivers on these. I was in hopes that with the DAQmx drivers this behavior was corrected.
I can conduct testing to determine this but would like to know ahead of time if this is still an issue.
Thanks

Thank you Ben for the answer.
I checked the article you referenced appears to me that I will be adding the physical address in the channel strings then do the voltage to temperature conversion and then correct the appropriate channels associated with the cjc in question. I will also need to adjust some on board jumpers for the SCXI 1120. If I am wrong please correct me.
If scanning the physical channel is possible as suggested in this article, would it not be possible to create the channel as a virtual global channel and reference it as the cold junction in Max? Then the temperature adjustment could be done at this level of acquisition rather than having to sort this out in the LabVIEW program. This takes me back to the days with LabVIEW 4.0 before we had the virtual channels and when we had to handle the temperature conversions and other scaling ourselves. Again if I am incorrect please let me know, for I would like to use the method recommended in the article if I don't have to perform all the calculations in the application.
Just wondering if anybody reading this has actually used this method. If so, how did it work for you?
I may end up building a start up routine testing for 1120 modules being used for thermocouple measurement then if found run a stop and restart scan every 5 minutes to prevent large errors from being introduced.

Scxi 1120 low pass filter specs for anti aliasing

Hia,
I'm am currently finnishing the development of a multi channel spectral analysis unit and I am concerned about aliasing. I have observed that the 1120 isolation amplifiers that I am using have a two position low pass filter for 4Hz and 10kHz now my problem is this, I'm sampling at 25600Hz and thus need to attenuate the signals by 12800, as i am using a 16bit AD card to be able to maximise its resolution I need to attenuate the signals to -92 dB (or -96 dB I can't remember which one) by this frequency.
does anyone have details of the 1120's 10kHz filter? can I get away with using this or do I need to use a speciallist anti aliasing filter (which wouldn't be as tough a filter as I am only interested in signals up to 5kHz so I could have a much slower roll off)\
Cheers
Any help would be appreciated
90% of all experts aggree that 1 out of 10 experts are wrong

The specific characteristics of the SCXI-1120 are not available because the filter is not high-performance since it is designed speicifically for noise rejection. From the SCXI-1120 user's manual (http://www.ni.com/pdf/manuals/320425d.pdf), you can see that there are two lowpass filter stages, and then there is also a bandwidth limitation imposed by the amplifiers. The two filter stages are simple RC filters, so I would doubt that the roll-off is steep enough to reach -92dB attenuation at 12.8kHz. I would recommend either designing your own first stage filter, like you had mentioned, or find a way to increase your sample rate.
-Logan

Differential input to SCXI 1120 with a 1305 input block - noise

Hello,
I'm trying to measure low amplitude, DC voltage signals using an SCXI 1120 with the 1305 terminal block. I'm picking up ground noise and I'm having a hard time finding my way through the manuals to solve my issue.
Currently I'm tieing the negative output of my load cell to the ground, as shown in the attached diagram. This is similar to Table 1, row 1, column 1 of the NI wiring document (http://zone.ni.com/devzone/cda/tut/p/id/3344).
Reading the 1120 user manual (http://digital.ni.com/manuals.nsf/websearch/7D3481BCFAA9E300862567EF0071F865), there are two setups for DC inputs in Figs 3-2 and 3-3. My current setup is similar to 3-2, but I have a CMV of zero, so this setup is not required. It seems that the setup in Fig 3-3 would be better for me, but I can't seem to use that configuration with the 1305 terminal block.
Fig 3 of the 1305 user manual (http://digital.ni.com/manuals.nsf/websearch/B02C64965878A95186257449005FBFAC) shows that you can link the negative to ground through a bias resistor, but specifies that for the 1120 this is to be left floating. In fact, in the text above Table 1 of the manual it specifies in italics that this be left in position G.
Is it possible to have the setup shown in Figure 3-3 of the 1120 manual using the 1305 terminal block? Should the setup that I have be okay? When I tie the load cell chassis to ground I get a noise signal that is periodic at 60 Hz (I'm in Canada), but has spikes and plateaus in it, but at low amplitue. If I remove the ground connection I get a relatively clean 60 Hz, sinusoidal noise component with an amplitude of ~0.5mV. My signal is at about 10mV, so this is significant for me. Using the second configuration I could digitally notch filter at 60 Hz, but I'd rather not.
Thanks for your help.
Attachments:
circuit.jpg ‏46 KB

Hello, Gorgeman!
I think you'll find this document useful: Referencing a Floating Input to Ground Using the SCXI-1305
Please let us know if you have any questions!
Will Hilzinger | Switch Product Support Engineer | National Instruments

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

LabVIEW 6.1
SCXI-1000
SCXI-1520
SCXI-1314
PCI-6031E
Windows 2000
Greetings-
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.
For example, if you set a gain of 100 on ch0 of an SCXI-1520, and you then create a Virtual Channel to read the mV output of the Ch0 sensor, (in this case a full bridge load cell), should the AI limits (range) that you specify in the Virtual Channel creation reflect the gain of 100 that the 1520 module is already applying to the signal? And after the 1520 module applies it's gain, does NI Max attempt to apply another gain if there is still capacity to amplify the signal within the AI range of the daq device?
Also, when measuring a full bridge sensor as an analog input voltage signal, and after performing a Null on the sensor, there is usually some residual offset. Does one then programmatically (in LabVIEW) tare, or zero this residual offset by subtracting its value from all subsequent measurements?
Thanks for your help.

Hello Steve,
How are you applying gain if not through a virtual channel?
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.
Sean C.

SCXI-1120 module

I am working a project where we want to measure temperature and pressure with LabVIEW. The pressure transducers put out a 4-20mA signal. My customer already has the following equipment. SCXI 1001 chassis, (2) 1120 modules, a 1320 terminal block and a 1328 terminal block. I am fairly new to the hardware side of this but it appears to me that I can use the 1328 with an 1120 module for the temps and the 1320 with the other 1120 module for the transducers with the 4-20mA signal. Are my assumptions correct? Also is the SCXI-1001 chassis powered by battery?
Thanks for any help.

Any DAQ card you choose will (as a rule) only use 1 input channel (channel 0) for data transfer between the SCXI chassis and the DAQ card. All of the data is multiplexed through channel 0 of the onboard DAQ card. So, you only NEED 1 analog input channel on your DAQ card. The 6011E is not the best choice for SCXI since you can not use the inherent (pseudo) SSH capability. In addition, the SCXI bus is band limited to a maximum aggregate sampling rate of 333 ksamples per second. So, the DAQ board would be limited to the 333 ks limit with SCXI. My personal favorite is the PCI (or PXI) 6052E board. It is rated at 333 ksamples per second at 16-bit accuracy - it is a superb match with the SCXI line.
As for the question about single-ended or differential
, well.., that is an entire DAQ lesson in itself. Simply put ... Single-ended means you connect the positive inputs to the designated channel and all of the ground are tied together. Differential means you attach the positive and ground inputs from each sensor to individual channels (see the appropriate users manual). Differential gives superior signal-to-noise ratio and commom mode noise rejection - at the expense of twice the channel count. The "gross rule-of-thumb" is: If your signal source is grounded (by means of a three-prong plug - say a stand-alone Vischay Amplifier) and the signal is greater than 1 V, and, the input wire is shielded and properly grounded, and, the wire length is less than 10 feet -- you can use single-ended: Otherwise, use differential.

Open thermocouple detection on the 1120

I am using an SCXI 1120 module with a 1320 terminal block to take temperature readings from k-type TCs. When we disconnect a TC the reading for that channel goes to around 272 C, which is in our measurement range. How can I get that reading to go out of range when the TC is removed?

Hello GlennXS,
All of the open thermocouple features I know of in NI hardware is taken care of in the driver. In addition to this, the hardware needs to support this functionality as well. The previous discussion should work well, but I do not know of a library that does this for you. All it really is is just 2 separate tasks (a resistance measurement and then a thermocouple measurement). You should be able to program this yourself using the DAQmx calls relatively easily. I would suggest looking at the example programs (C:\Documents and Settings\All Users\Documents\National Instruments\NI-DAQ\Examples).
If you give me more details about the hardware you have and what you have tried, then I can try and help you out more.
Neal M.Applications Engineering National Instruments www.ni.com/support

Bad REadings

I found out that the virtual channel system is kind of problematic with my system. One of the NI engineers recomended me to use those, specially because they perform CJC on every reading automatically, and I did. But I wasted a lot of effort just to discover that the AI Read VI doesn't update the CJC on every reading, what is done only in the setup.
Here is the spec of my systgem:
- SCXI-1000
- SCXI-1200 connected in the parallel port and controling the chassis, with connector block 1302, and using its counter resources.
- SCXI-1163, controling a few switches with connector block 1326
- SCXI-1120, reading T thermocouples, with connector block 1327.
- LabVIEW 5.1f1
- NI-DAQ - 6.9.1f28
- IBM Personal Computer 300 GL, with Pentium II 266 Mhz.
I dicover
ed that the Virtual Channels weren't that good using the "SCXI Scan VI", provided with the package. I configured a single virtual channel and started an acquisition, returning me NaN. Then, using the SCXI Scan VI and configuring everything manually, I could get some results. I have tried so many things to get it working that the possibilities are almost over.
Anyway, the error I get most is code 10800. I tried to slow down the Scan Rate, increase the samples/channel, increased the time limit, checked all jumpers, reduced the gain, set the same gain for all channels, connecting and not connecting "-" channel to ground, tried to split the daq into 2 readings of 4 channels instead of 1 of 8, (and maybe some other things I can't remeber now) and nothing seems to work. The other modules work well. Also, it's important to say that I got the same DAQ problems with the VIs provided with LabVIEW. A funny thing is that some times, the DAQ works, sometime, it doesn't. Of course, I am comparing
in exactly the same conditions, i.e., turning everything ON, then first loading LabVIEW and starting a acquisition. This is really strange.
I hope anyone can help me!
Thanks,
Guilherme

Since you are getting a time out error (10800) it would worth to check that the SCXI-1200 is responding. In the measurement and Automation Explorer, select the SCXI-1200 under devices an interfaces, right-click and go to properties. Click on "test resources" and you must get "The device has passed the test" If not that could be one possible reason of the problem.
Can you get readings directly from the SCXI-1120 by using the SCXI string? This does not mean necessarily the CJC sensor:
"You need to use SCXI channel strings to communicate with other modules in the SCXI chassis. The general format of the SCXI channel string is OBz!SCx!MDy!a, where z is the device number of the DAQ board connected to the chassis, x is the SCXI chassis number, y is the module nu
mber, and a is the channel number (use a:b to scan multiple channels). The SCXI channel string is not used for the SCXI-1200 because it is its own DAQ board."
The Virtual channels should not represent a problem, that is why is important to make sure that teh system is working fin without them too.
Thanks for contacting National Instruments!
Arturo Q.

Ni-daq

Adquirimos un modulo scxi-1125 para reemplazarlo por el scxi-1120 en nuentro sistema de adquicision de selñales formado por una daq at-mio-16-de10, pero la versión del ni-daq (6.1) no soporta al modulo scxi-1125, debido a esto cambiamos de version del nidaq al 6.9.0, pero esta version en cambio no soporta a la daq at-mio-16-de10, que puedo hacer al respecto, cual seria la solucion?????????

Hola, que tal?
Estuve checando varia documentacion y la tarjeta AT-MIO-16DE-10 (version corta) si esta soportada por la ultima version del driver (NI-DAQ 6.9.3). Si usted tiene la version corta de esta tarjeta, usted la podra utilizar sin problemas junto con el modulo SCXI-1125.
Si usted tiene la version larga de la tarjeta (revision D o previa), entonces la unica solucion para que el driver sea compatible con todo el sistema (SCXI y DAQ), seria comprar otra tarjeta DAQ que este soportada por el nuevo driver y que se pueda usar con el 1125. Una tarjeta de la serie E de bajo precio como la NI 6025 o NI 6024 podria servirles. Para mas informacion, puede consular la siguiente pagina:
Data Acquisit
ion Hardware
Saludos y buena suerte en su proyecto.

Can you slow the scan rate of VI Logger scans per minute

Can you set up a logging task with VI Logger to log 1 scan per minute? I'm using a DaqCard AI-16E-4 and SCXI 1120 Module.

What do you mean by VI Logger? The easiest way to do what you need is to create a while loop and put in it one of NI's "easy-IO" analog input VIs and a wait function set to 60,000 milliseconds. Depending upon the acquisition VI you use the result would read either one point, or a set of predefined points once a minute. (see attached code)
How much more complicated the application would get depends on such things as what exactly you want to do with the data, and how you want the user interface to react. For example do you need to save the data? If so, you'll need to add a file save function to the loop too. Also, the simple version I attached could take as long as 2 minutes to quit once you press the stop button--which probibly wouldn't be acceptable.
The point is that the basic functionality you asked for is very easy to do. The complicated part is defining all the other stuff that wraps around that simple functionality.
Mike...
Certified Professional Instructor
Certified LabVIEW Architect
LabVIEW Champion
"... after all, He's not a tame lion..."
Be thinking ahead and mark your dance card for NI Week 2015 now: TS 6139 - Object Oriented First Steps
Attachments:
daq_demo.vi ‏19 KB

Error in counting.

Hi,
I am using the measure buffered period vi from LV 6.0 to measure the time averaged period of a square wave. I am using the signal as the gate and the internal clock as the timebase with a frequency of 100KHz. The problem i am having is that the VI does not produce the right output. About 60% of the time the value is right but the other 40% it is wrong and it seems that it is missing a pulse from the signal and counts double the period/ half the frequency. I am not sure why this is happening. Also this error gets worse as i increase the time base. I have grounded the signal appropriately so that shouldnt be an issue. Is there any way to rectify it? Is there some technique using the other counter i have on the board (pci-6052e) to resolve this.
Thanks in advance,
Shyam Menon.

Hi Shane,
I should have done this before but i am posting a section of my code now. The top parts are about scanning the analog channels connected to my scxi 1120 module and the bottom part is for scanning the counter pin. Since i read the pci-6052e has 3 dma modules, i shouldnt hopefully have problems with data transfer. Another thing i found is that i need to have sufficient delay time in the read buffer vi so that all the data gets written to the file otherwise i am missing some of the data. Hope this helps you to understand my problem better.
Thanks,
Shyam.
Attachments:
Mod_Engine_VI.vi ‏131 KB

New Uses For Our Current Dyno Thermocouple DAQ System

Hello,
Currently we are using this setup to collect data in our high temperature dyno.
SCXI-1001 Chassis
4 - SCXI-1120 -> SCXI 1320 units
8 - SCXI-1102 -> SCXI 1303 units
feeding into a PCI-MIO-16E-4 (PCI-6040E) DAQ system.
Also available are a SCXI-1000DC chassis, TC and BNC 2095 terminal blocks, and SXCI-1104 multiplexers.
The sensors we are looking to use have a 4-wire connection consisting of V(excitation),Common Ground, V(output), and V(offset). I would like to know if there is a way we can use the current equipment we have available to provide the 5v excitation source needed, as well as collect the V(output). Any help regarding the appropriate setup or wiring would be greatly appreciated. Thank you in advance
-Jason McBride

Hi BigChief,
If you're providing an external excitation voltage to your sensors, you should be able to use either the SCXI-1102 or SCXI-1120 module, with their respective terminal block, to perform voltage measurement (provided the signal is within the module's input range). You can wire V(output) and Common ground as input to one of the channels on the terminal block. If the V(offset) is used for zeroing the measurement, you can wire that into a second channel, take the measurement, and subtract that value programmatically. If you're setting up a virtual or global channel, select the measurement type as "voltage" instead of "temperature".
I hope this helps.
Thanks,
Lesley Y.

Estimating product life

I have several test stations that primarily have the following types of hardware:
PCI 16 series E DAQ Boards
SCXI 1000 & 1001 Chassis
SCXI 1102 Input modules
SCXI 1163 HV
SCXI 1162 HV
SCXI 1120 Input modules
SCXI 1125 Input modules
Some of these products are over seven years old now.
My question is this. Is there a good method of estimating failure rates for these products? I know this is a loaded question as application of the product will be a large factor in determining the mean failure rate. However, I still must budget for replacement or repair of these items. I appreciate any suggestion you might have on how to estimate this.
Thanks.
Randall

Hello Randall,
Thank you for posting to the NI discussion forums. I believe what you are
looking for is the mean time before failure (MTBF) for the devices you listed.
National Instruments does not publish this information. Please create a
service request at www.ni.com/support for further information.
Regards,
Jesse O.
Applications Engineering
National Instruments
Jesse O. | National Instruments R&D

SCXI-1120 Gain

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