How do I wire my SCXI-1520 quarter bridge completion in parallel?

I have a quarter bridge set-up using the qtr completion in the system. In parallel with my strain gauge I'd like to have another resistor. I'm using the strain gauge as a dummy, and am interested in the current traveling in a parallel path through a film resistor as I change the film thickness. However, I'm not convinced that what I've wired has the strain gauge and other resistor in parallel. I have the strain gauge wired to: P+, QTR, S+ and the other gauge wired to QTR, S+.
Thanks!

Greetings,
You will want to wire the other gauge between P+ and QTR or between P+ and S+. To make this decision, you will need to determine how the lead resistances will affect your measurement. Page 2-4 of the SCXI-1520 User Manual (link available below) contains the wiring diagram for Quarter-Bridge Configuration I.
SCXI-1520 User Manual
Good luck with your application.
Spencer S.

Similar Messages

SCXI 1520 quarter bridge setup will not output excitation voltage, but full bridge will

My SCXI system will not output an excitation voltage to the quarter bridge(verified with voltmeter). It works for a full bridge setup. When connected to a 'quarter bridge I' configuration, I can use MAX to null and shunt calibrate. The quarter bridge circuit appears to be balanced after the calibration, but the calibration results post a software gain factor close to zero, as well as a close to zero excitation voltage (eventhough I have the voltage configured for 5 volts). I have the SCXI 1520 module, the virtual channels, and the wiring properly configured (several years experience with this device). I'm using an old E series DAQ card AI-16XE-50, with the 50 pin cable that plugs in the back of the SCXI chassis. I noticed I had two bent pins with the cable connector module that plugs into the SCXI backplane. I was able to straighten them, so the cable connects properly, but I suspect the bent pin incident caused electrical circuit damage. Any suggestions on trouble shooting? None of the three 1520 modules I have will output an excitation voltage for a quarter bridge.

Sorry that I don't have an answer for you tyea, but I'm interested in your thread because I have a similar issue with a 1520. My excitation votltage, as measured with a DVM, is always 1V. I've tried 0V, 1V, 5V --- it's always 1V, on Full or Quarter bridge. I'm using a similar DAQ to yours - a PCI 16XE-10 (and a PCI-6030E on antother system).
I don't have a lot of experience with these modules. This could be a wiring or programmatic thing I'm doing wrong.
Richard

How to connect 2-wire strain gage to NI 9237 by quarter bridge

I have a Strain Gage: KYOWA KFG-20-120-C1-11 (2 wire) http://www.kyowa-ei.co.jp/english/products/gages/pdf/kfg-01.pdf, NI 9237 on a Compact DAQ (cDAQ 9174) and RJ-50 (10-pin modular plug to pigtail wires).
Strain Gage features:
Gage Factor: 2.08 +/- 1.0%
Gage Resistance: 120.2 +/- 0.2 Ohms
I'd like to connect them to measure the strain with quarter bridge configuration but I have some doubts about which line goes to which terminal.
Thanks.
Solved!
Go to Solution.

You can find the manual for the NI 9237 module here
It's a good idea to buy an NI 9944 or NI 9945 Quarter Bridge Completion Accessory if you're planning on using this module with a quarter bridge configuration, but you can look at the following diagrams to see what kind of internal connections are implemented: Connecting Strain Gauges and Shunt Resistors to the NI 9237
PS Posting in the DAQ or signal conditioning forums instead of Labview may get you better/faster answers.
Cheers
Message Edited by mishkin on 03-11-2010 02:40 PM
Misha

Quarter bridge for 9237

How do I select quarter bridge completion settings for 9237 with 9944?
Message Edited by Frederico Barros on 09-28-2007 09:02 AM

The 9237 is capable of full and half bridge measurements without addition equipment. In order to take quarter bridge measurements with the 9237 you need a quarterbridge completion resistor component (like the ni 9944). This turns your quarterbridge configuration into half bridge, which the 9237 can do. You will need one of these completion components for each of your strain gauges.
[will work for kudos]

How can I use LabVIEW to ground floating SCXI-1520 channels (in order not to lose scanning capabilities from the multiplexer)?

Currently I am reading quarter bridge strain with several SCXI-1520s. When in MAX I noticed my values were no longer reading after a certain gage and as I attempted to troubleshoot, found out that the multiplexer in this module will not scan past any open channel (or if it does, channel results are not consistent) for a very logical reason. If I lose a gage, I usually lose any data from any subsequent gages which we really cannot afford.
Are there any suggestions programming in LabVIEW (right now i'm using NI-DAQmx with an analog task set up)so that each time my loop executes, the program will check for any open channels and either not collect that data or change the order of acquisition (i.e. place the open channels last on the scan list?
I'm open to anything that might be of help

Yes, by "open channel" i mean that there is no signal returning from the gage because it has broken off the structure or the signal to the terminal block has been disconnected somehow.
When I lose data, I'm referring to the data that is acquired on following channels. The behavior appears to be fairly random (which was a troubleshooting nightmare ) but usually if a channel is open, then that and those behind it in the scan order do not return any data. It returns a number like 10.357E-6 and I do not pick up any noise or fluctuations. As far as I understand, the multiplexer stops scanning at this point (open channel) because it has nothing to ground to and subsequently "hangs" - not (or randomly) scanning the following channels. I have gone through the bridge configuration and as of yet, have not figured out how to fix this using any hard-wiring techniques. I emailed NI, and was sent a library file to "ground the channels" but it actually resets the Analog input Task I have defined each loop.
I am new to NI-DAQmx so I do not know if this will alter any configurations I already have in MAX for NI-DAQmx. Will it override? I am concerned it will slow my loop time, and also I cannot see the code for this sub.vi so am a little skiddish about using it if i do not know if it can be tailored to my app.
What do you think? Am I on the right path?

How do I connect 16 strain gauges in quarter bridge arrangement to a SCXI 1322 connecter block?

Specifically, do I connect 4 bridge completion resistors to each VEX- channel or do I need to wire them together somehow first?

I have attached a bitmap image that explains how to wire a quarter-bridge strain gauge to the SCXI-1122 (with 1322 terminal block.) The 1122 only provides half-bridge completion, so you have to wire an extra resistor into the circuit to complete the bridge.
You can find this image in the SCXI-1122 User Manual, which is available for download at:
http://search.ni.com/search/query.html?col=alldocs&qp=%2Bcontenttype%3Aproductmanual&lk=2&layout=ProductManual&qt=1122
Attachments:
1122_strain.bmp ‏920 KB

How do I deal with a cascaded system, First Stage SCXI-1520's and Second Stage SCXI-1143's?

I am aware of the following link:
http://digital.ni.com/public.nsf/allkb/653505DF63AD04E686256DD7005D42F6
I'm kind of stuck here. The system is already in place. 1520's in first stage and 1143's in second. I am supposed to configure the 1520's and scan the 1143's.
What problems do you see with this?
How do I go about doing an end to end calibration?
Should I just rip out the 1143's and hope nobody notices?

Hello Frank,
Let's start from the beginning. I understand that you have some SCXI-1520s and 1143s that you are using in your measurement system. What type of sensors are you acquiring data from? It seems that you intend to use the 1143s to filter the data between the 1520s and the software. Is this correct? Another question that I have is what do you mean by "end to end calibration?" The more specific that you are about the application you are developing, the easier it will be for others to help you with any questions that you might have.
Looking at the knowledge base article that you linked in your original post, it seems that the point was to filter the data from the SCXI-1520 in software, using the LabVIEW Filter Express VI. Would this be a viable option for you? If so, then you could just rip out the 1143s.
Regards,
Wallace F.
National Instruments
Applications Engineer

SCXI 1520 for load measurement cable lengths of 500 meters

HI ,
I ned to measure lod from a 1000 ohm full bridge circuit. The distance between the sensor & my SCXI 1520 is 500 meters. Please let me know how can I compensate for the lead resistances both in Excitation & while reading back the actual sensor value.

grte,
For extremely long cable runs resulting in much higher than normal lead resistance to bridge resistance ratios, you must use remote sense, which is a six wire connection (four wires for excitation and two for signal). Refer to your SCXI-1520 manual for more information: http://www.ni.com/pdf/manuals/372583d.pdf, specifically page 2-9 and Chapter 4, Theory of Operation.

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.

Using SCXI-1520 in Parallel Mode.

Hi all,
I am using SCXI-1000 chassis and PCI-1024E DAQ card.
I want to use my SCXI-1520 in Parallel mode.
Is there any other way to configure my 1520 in parallel mode other than directly connecting to DAQ board using SCXI-1180 feed through panel and SCXi-1302?
Some of my friends are telling that there are some Patch files, through which we can use the scxi-1520 in parallel mode. Is it true? If it is true please give me how use the Patch files( or alternative solutions).
Thanq
Regards
Preetam

Preetam,
As explained in the SCXI-1520 user manual, Traditional NI-DAQ does not support true parallel mode operation of the SCXI-1520. However, NI-DAQmx does. I would recommend installing NI-DAQ 7.2, which includes the latest version of both Traditional NI-DAQ and NI-DAQmx. Then you can use the NI-DAQmx driver to control your SCXI-1520 in parallel mode. To configure the SCXI-1520 in parallel mode with NI-DAQmx, simply select the Parallel Mode check box when setting up your chassis and modules in MAX. I hope this information helps.
SCXI-1520 User Manual
NI-DAQ 7.2 Download

SCXI-1520 Zero Offset Changes with Variable Loads

We are using the SCXI-1520 to calibrate sensors based on strain gauge bridges. The problem I'm having is that the offset changes when changing the bridge resistance. For example, the output reads 0.0000 mV/V for 350 ohm bridges. It reads 0.0112 mV/V for 700 ohm bridges. It reads 0.0135 mV/V for 1000 ohm bridges. The signal input is a constant zero for all three of these examples. The span (gain) is very consistent. In other words, changing the bridge resistance does not affect the gain. I know the excitation sense lines are working and they are applied very near the bridge. Enabling or disabling the autozero mode makes no difference. What can be done to eliminate the variable offset when changing the bridge resistance?

Dear Dj143,
Are you calibrating your strain gauge lines in the Measurement and Automation Explorer (MAX) or in your LabVIEW program?
In MAX you can create a task and use the calibrate tab in the task to calibrate your line. You would then call the task in LabVIEW. If you are using this method, make sure that you are specifying the correct Gage Resistance (gauges in an unstrained position). The default is 350 so it would make sense that you are getting 0 V with this resistance.
In LabVIEW you can use DAQmx Perform Bridge Offset Nulling Calibration.vi to calibrate your lines. There is an example in the Example Finder that shows how to use this VI. (LabVIEW Help menu>>Find Examples. Search calibration. Cont Acq Strain Samples (with Calibration).vi). In this case make sure that you are specifying the correct Nominal Gage Resistance (gauges in an unstrained position). Once again the default is 350.
If you still get incorrect voltages when specifying the correct resistance, let me know how you are calibrating your lines and I will see what I can think of. Have a great day!
Sincerely,
Marni S.

Scxi 1520 exitation of 11 -30 vdc

Hello
I want to know wether i can use a device in my strain (scxi 1520) gauge module which requires an exitaion of 11-30 vdc and gives an ouptput of 4-20 mA.if possible whats the configuration and if not ,if i provide an external exitation how do i use it with my scxi 1520 module..
plz its urgent
lalit

You can convert almost any current output to a voltage output by adding a resistor across the output terminals. Calculate the resistor such that the voltage across the resistor at max current does not exceed max input voltage of the acquisition system. Also, check the specs for max output voltage of the signal source. Don't expect the circuitry to supply more than the circuit supply voltage minus, say, 20 p.c.
Of course you will have to compensate the offset - at 4mA 'live zero' output you will of course get a reading different from zero. This should be possible by software.
However, if you need an excitation voltage higher than supplied by the board you can use an external power supply. Maybe you will have to use a grounding scheme different from what be used with an 'internal excitation' source (from the board).

SCXI 1520 measurement in microstrain

I am trying to acquire samples from several SCXI-1520 channels and save / display them as microstrain instead of strain (calibration factor of 1,000,000) while at the same time applying a different calibration factor to two other channels acquired using an SCXI-1141. I basically want to know how to apply different calibration factors to several different channels using DaqMX. I have been chasing my tail with this for several days and I think I have just about exhausted all of my options...any suggestions would be greatly appreciated.

Hi Dave,
It sounds like what you're looking for is applying custom scaling to different channels. There are a couple of ways you can do this. The easiest would be to use the DAQ assistant and apply a different scale for each channel. You would just need to set up a custom scale for each type of scaling you want. You can set up the scales from here:
This would be quick and easy, but if you don't want to use the DAQ assistant, you can set this up in DAQmx directly. Probably the quickest way is to configure a task in Measurement and Automation Explorer (MAX) with the channels and scales (similar to the DAQ assistant setup). You can then drag that task over to LabVIEW, right click on it and select Generate Code>> Configuration and Example. This will generate the code for you, and give you a good example to work off of later. You could also just build the code yourself by setting up scales in MAX, and configuring your code like so:
Hope this helps,
Andrew S.
National Instruments
Message Edited by stilly32 on 11-03-2006 10:49 AM
Getting Started with NI-DAQmx
Measurement Fundamentals
Attachments:
multipleScales.JPG ‏65 KB
DAQ_asst_Scale.JPG ‏107 KB

Applying Excitation Load to the SCXI-1520

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...

In my opinion, I don't think it is worth the trouble. The temperature
of the SCXI-1520 probably won't change much from connecting a load to
the exictation since there is plenty of heat generated from the
SCXI-1520 to keep it at a stable temperature with or without the
excitation source being connected. A bigger concern would be that
strain gages can have self-heating errors when current is applied,
which is usually accounted for by using a Quarter Bridge Type II
configuration with a dummy strain gage next to the active gage. These
self-heating errors occur when the strain gage is connected to the
excitation source - so if you wanted to keep anything "warmed up" it
should actually be the strain gage that you are disconnecting; not the
SCXI-1520.
-Logan K

How to get the first and second quarter from CRT

Dear Freinds,
                I have one scenario , the Functional SPEC says Read the payroll results and from the CRT get all the 4 quaters
for the wage type /5UH and sum them and then pass on the to field in the main strucutre.
Iam using the FM HR_GET_PAYROLL_RESULTS
CALL FUNCTION 'HR_GET_PAYROLL_RESULTS'
    EXPORTING
      pernr                         = fp_v_pernr
      permo                         = fp_v_permo
      pabrj                         = fp_v_pabrj
      pabrp                         = fp_v_pabrp
      actual                        = 'A'
    TABLES
      result_tab                    = i_payresult
    EXCEPTIONS
      no_results                    = 1
      error_in_currency_conversion = 2
      t500l_entry_not_found         = 3
      period_mismatch_error         = 4
      t549q_entry_not_found         = 5
      internal_error                = 6
      wrong_structure_of_result_tab = 7
      OTHERS                        = 8.
Iam collecting all the Actual Result (current result) values
on the selection screen iam passing for month april (04 2008)
so this falls in the second quater .
the internal table   i_payresult is picking up only the second quater (01-04-2008 to 30/04/2008 ) ,but since on the selection screen iam pasing as other period (04 2008) the internal table i_payresult returing from the FM (HR_GET_PAYROLL_RESULTS) only   picks the second quater,
could any one let meknow how i can pick up the first quarter as well and add the first and second quater to mee the requirement .
Please help me in this regard
Thanks & regards
maduri

Hi Manoj,
             Thank you for giving me idea for going further regarding this problem , so my final question for this is
as per FS they said they are going to enter the payroll
area and the other selection as 04 2008
In order to achieve the first quarter , because 04 2008 means they are going to enter for the second quarter , the payroll results will come only for second quarter and not for the first quater , if they want to sum all the two quarters then they shouldnt pass on the selection screen   the dates as 04 2008, instead they has to pas
01 01 2008 to 30 06 2008 , as there is no point in they passing as 04 2008 as we are going to consider from 01 2008 to 062008 .   Please correst me if am correct regarding the dates passing on teh selection screen
or if the user enters on theslection screen still enter 04 2008 and will be able to acheive the first quarter ??
Please answer me this point before i can change the logic of the code and tell to my FO regarding this point.
thanks & regards
Madhuri

How do I wire my SCXI-1520 quarter bridge completion in parallel?

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