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.

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SCXI 1520 for potentiometer type pressure sensor

I am usig 1520 for bridge type pressure sensor data acquisition.
I have a requirement for potentiometer type pressure sensors. The sensor is a potentiometer that needs 5V exciation.
+---------------- Exc+
|
|
+--+
| |
| |
| |<-------------- O/p+
| |
| |
+-+
|
|
+---------------- Exc-
I was wondering if I could use 1520 for interfacing with such sensors?
I am hoping I can short P- and S- lines and connect to Exc-. P+ would be Exc+ and S+ would be O/p+.
The resistance between Exc+ & Exc- is of the order of 1-5 kOhm. So the current drawn from the excitation supply is of no concern for the 1520, I believe.
Can I do this with the 1520?

Dear Cas,
Thanks for your enquiry. You have obviously done a great deal of research into this matter already. I am afraid that it is unlikely that you will be able to use a single SCXI module to carry out all the functions you have listed. As accelerometers require such specialised conditioning, it will require a dedicated module - as you already mentioned, something like the 1530 (4 channel accelerometer input module) would be ideal.
However, you have a number of different options for the pressure, voltage and temperature measurements.
For example, you could purchase a 1520 mudule for your pressure measurements, and then use a general purpose 1102B for the voltage and temperature (you would require the 1303 isothermal terminal block to condition the thermocouple readings... and bypass the CJC technology for the voltage readings).
Or, perhaps you could use the 1102 thermocouple module for your temperature readings, and then use a 1102B to take the voltage and pressure readings. Obviously this would involve making your own bridge configuration for the pressure sensor, but that should be fairly easy.
Before you make any final decisions, I would recommend that you call your local branch of NI and speak with a sales representative. Perhaps, a member of the field sales staff could actually come to see you to discuss the matter face to face.
lastly, it sounds like you have a relatively high channel count for some of your readings, which is why you have decided to use the SCXI platform. I was just wondering if you had considered compact DAQ (cDAQ), which combines DAQ hardware with signal conditioning. Higher spec, ease of use, lower channel count. Swings and roundabouts I guess.
I hope this has been of some use to you.
Best wishes,
Rich R
Applications Engineer
National Instruments UK & Ireland

SCXI 1520

Hi,
I have a DAQ card PCI 6036E. I want to use Signal conditioner SCXI 1520 for my measurements. What are the accesories required for the installation of SCXI 1520.
Priyank
Solved!
Go to Solution.

Hi evereybody
Iam fairly beginner with Labview 2012 to create a gain-settings of SCXI 1520 VI.
I would like configurate gain from scxi 1520 analog inputs with labwiew and find in user manual a tool for this.you can see the picture.
But this VI isnt executable,because i have labview 2012 with newest daq driver.
This tool works with old daq driver. New daqmx cannt find this files.
AI Parameter
AI Config
AI Read
can any person help me?
Thanks.
Attachments:
Gain1520.jpg ‏122 KB

E1 Cable Length Limitation

I need to know the E1 cable length limitations,in meters? Actually i've a customer who needs to extend their E1's from the basement to DataCenter Room and you people know the UTP Cable limitation. So which type of device should i refer to them for this purpose.

UTP gauge 22, typical attenuation, should cover 1000 feet ( > 300 m) without problem.
Make sure you use proper cable and respect the pair twisting, that is NOT like ethernet.

Cable length limit on the so-called "Internet" port?

Is there a limit on the cable-length when connecting an Ethernet cable to the so-called "Internet" port on a WRT54G router?
I assume this is a standard 10/100 Ethernet port, since I am connecting this to the Ethernet port of my DSL modem. Since the Ethernet standard defines a maximum cable-length of 100 meters when connecting any 2 Ethernet devices, I should be able to use a cable up to this length when connecting 2 Linksys routers together.
Here is what I want to do:
DSL Modem-->Linksys Router-->Linksys Router
My first Linksys WRT54G router is connected to a DSL modem. I want to put a second WRT54G Linksys router in a different building, and connect them with a 100 meter Ethernet cable, connecting the remote end to the second router´s "Internet" port, and the other end into one of the first router´s available 10/100 ports. This will allow me to create 2 wireless signals, with 2 different DHCP scopes and 2 different SSID´s, basically allowing me to extend the range, with the 2 routers connected with a physical wire.
This works when connecting them with a short, 2 meter cable. Using a short cable I am able to associate with the second router´s SSID, get a DHCP address from that router, and then turn on RIP on both routers and have traffic route from the second router to the first one and out to the Internet successfully.
However, when I replace the short cable with a longer one, either 80 meters or 100 meters, I don´t get a link light between the routers. I do get a link light if I connect to a 10/100 port on both routers, but RIP doesn´t seem to want to exchange routes on the second router out anything other than the "Internet" port. Moving the cable back to the "Internet" port fails to produce a link light (unless I use a really short cable, which does produce a link light).
So my question is this: from a Layer-1 perspective, is the "Internet" port an Ethernet port that enforces a cable-length limit that doesn`t follow the standard 100 meter rule?
--- Christer

well..the internet port is definitely an ethernet port...however, it is not supposed to limit the cable length .. try a 50 m cable and check whether it works...because my friend had a similar kind of an issue and it worked fine with a 50 m ethernet cable ..

Looking for Video Camera to measure crack length??????

I need to measure crack length in fatigue test of an Aluminium sample automatically. For example, the camera can take shots (Images) every 4000 cycles (fatigue load cycles), maybe more cycles.
For my test, I need to measure both sides crack length (right side and left side of specimen centre line), shown in Fig1. So I need to take shots both crack tips at the same time, which means camera must have a large field view and the resolution should measure 0.01mm, to see both crack tips clearly. At the end, I must be able to acquire images from Labview. I can save all the images into my fold from Labview, then I can measure crack lengths in left and right side from every image.
Would you please give me any suggestions on the characteristic/specifications of this kind of camera?
What kind of camera can I use? How much this kind of camera? Where can I order this kind of camera?
Attachments:
camera-Fig12.jpg ‏16 KB

Do you have the software that will analyze your images? If not, your camera is not your major cost here.
But for just cameras, check out edmund optics (edmundoptics.com I think). They have a camera selector guide that will at least give you an idea of the specs you actually need and the price range to look at.

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 excition measurement

After setting the excition voltages of the SCXI-1520 either with MAX or the AI Parameter.vi, I can read back the value for a given channel with AI Parameter.vi's "Get" function or with the SCXI channel strings "ob0!sc1!md1!p_posX" & "ob0!sc1!md1!p_negX" (where X is the channel number).
The values reported are slightly different than the commanded value. Which of these is the most accurate value of the actual voltage?
Rich

Greetings Rich,
Using the SCXI channel strings will actually read back the excitation voltages using the A/D of the DAQ device cabled to the SCXI chassis. Using the AI Paramenter VI to get the excitation value will just read the NI-DAQ configuration file and return what you set the excitation value to within MAX or LabVIEW. So the AI Parameter VI should just be used to ensure that the excitation was set (this isn't actually reading the excitation voltages using the A/D of the DAQ device).
So, reading with the SCXI channel strings will allow you to confirm the voltage levels of excitation. Using the AI Parameter VI will ensure that the setting for excitation has taken affect.
I hope this helps. Let me know if you have additional questions. Have a great day.
Regards,
Todd D.
NI Applications Engineer

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

SCXI-1520 AND 700 OHM LOAD CELL?

Will the SCXI-1520 work with a 700 ohm full bridge load cell? I'm a load cell mfg proposing a 700 ohm load cell solution to a customer. He says he doesn't think the 700 ohm cell will work with his 1520. The load cell will can take a maximum 20 VDC excitation and outputs 2 mV/V.

Hi,
Can you verify that the voltage coming out of the thermocouple is correct? You can do this by measuring across the thermocouple using a hand held multimeter. You may also want to input a known voltage into the module (a simple battery would suffice) and see if this produces the correct voltage in Measurement and Automation Explorer.
Abhinav T.
Abhinav T.
Applications Engineering
National Instruments India
LabVIEW Introduction Course - Six Hours
Getting Started with NI-DAQmx
Measurement Fundamentals

Maximum cable lengths for USB / FW / DVI & sVGA?

I've hunted around on the net and can't find any kind of definitive answer regarding maximum cable lengths for USB, Firewire 400/800 and DVI / sVGA monitors. Can anyone shed some light?
I'm about to shift my studio into a new room, and have the oppourtunity to stick my G5 and external drives into a corridor cupboard adjacent to where my studio is - in other words, noise free bliss! But....
...if I map out how far my computer monitors, keyboard and audio interface will be from the cupboard, and take into account the twists and turns involved in neat routing, I'm looking at a distance of about 10 meters. I need to know if any of these devices will be OK with such a long run of cable, and if not, if it's possible to achieve a good result using hubs or repeaters?
So, can anyone help me out with info on:
an Apogee Ensemble (Firewire 400)
an Apple keyboard (USB 2.0)
an LCD flatscreen (DVI)
and another LCD flatscreen (sVGA)
Many thanks!

I was just researching the very same thing, though it does not sound like my studio setup will be as sweet as yours. Here are a few things I ran across:
FIREWIRE-
"The maximum cable length specified by the IEEE1394 standard is 4.5 meters. However, more recent tests have shown that certain high quality firewire cables can achieve longer lengths without significantly affecting transmission quality. Several manufacturers sell firewire cables longer than 5 meters (some up to 50 meters)."
~http://www.focusrite.com/answerbase/article.php?id=206
I found an example of a company who claims to sell a firewire cable of that length:
http://www.expansys.com/pf.aspx?i=102956
USB-
There is forum discussion on the topic I was reading yesterday:
http://www.everythingusb.com/forums/showthread.php?threadid=804
But don't go past the 11th post or so, they go off on another subject... the use of hubs & the words "active extension" in that post caught my eye. A quick google search came up with this site:
http://www.everythingusb.com/forums/showthread.php?threadid=804
There were a bunch sites with devices claiming to do this.
Finally I have this chart, which seems to support what what the articles say, without of course any other extension technology/solutions:
http://www.extron.com/company/article.aspx?id=dedigform10
I'm not making any claims at all about how true these sources are, I just have the same questions and decided to toss what I've been looking at into the discussion. Feel free anyone to jump in and tell me its all wrong - I'd love to hear whats right.
~sam

Max cable lengths for voice links

Hello everybody,
I would like to get an info on max. cable lenghts for FXS, ISDN BRI (only p-t-p config) and ISDN PRI connections between PABX and Cisco VoIP gateway, especially that regardig ISDN. I have info from some standard. spec, but want to know the Cisco environment. I didn't find anything useful on CCO..
Thank you very much for your valuable and prompt help.
Peter

Hi,
thanks for that. I've seen a document on the VWIC-MFT-E1 that states the max cable length is approx 600m.
http://www.cisco.com/en/US/products/hw/routers/ps274/products_tech_note09186a00800b6e0f.shtml
Where did you get the 200m from? do you have a reference doc you could point me at?
Stuart

Max USB cable length for LT1421

Does anyone know how long the USB cable can be for connecting the LT1421 flat panel to the computer?
The screen is delivered with 1,8m but I must place the panel in a least 6 meter distance from the computer, is that possible?
I know that the max length for USB 2 is about 5 meters, but it varies between products how sensitive they are to cable length.

3 meters for USB1 and 5 meters for USB 2. You can find lots of information on the subject with a quick search. Try http://www.usb.org/about/faq/ans5 for starters. It explains how to get up to 25 meters of USB cable when you use several USB hubs.

Minimum Fiber Patch Cable Length for MGBSX1

I want to "stack" a couple 300 series gigabit switches with fiber using a pair of MGBSX1 GBICs and a single LC to LC patch cable.
Is there a minimum supported patch cable length in this configuration?

Howard,
Thank you for posting. You should have no issues using a short fiber patch between the switches. Just make sure the fiber doesn't bend too sharply and get damaged.

SCXI 1520 for load measurement cable lengths of 500 meters

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