Multiple scxi 1127 switches scanning, dmm 4070

Hi,
I am using 2 switches SCXI-1127 in a PXI/SCXI combination chassis. The readings are done through a dmm 4070.
I need to scan 60 thermocouple channels, i.e. 32 on the first one and 28 on the second switch. Now, I found http://zone.ni.com/devzone/cda/tut/p/id/3658 stating that a scanning multiple SCXI switches is using legacy DAQ functions in niSwitch for these specific siwtch cards (1127).
What version of niSwitch was it? Is it still true now? Why is that? Or should I use the new way using DAQmx?
thank you
alex

Hi Alex,
This is still the case with NI-Switch 3.3.1. Due to hardware limitations, scanning multiple SCXI-1127 modules is not a simple task with the NI-Switch driver. I would recommend using the DAQmx example "DAQmx Multi Switch Synch.vi" if you are performing synchronous scanning. I have taken a screen shot of the front panel of a working VI to help get you started.
In general, it is more efficient to use DAQmx when scanning multiple switches. When using NI-Switch to scan multiple switches, it is necessary to maintain a session for each switch module. When using DAQmx Switch, you need only open one task. Using DAQmx Switch increases programming efficiency, keeping your code neat and maintainable.
If you need further explanation or if you have further questions, please let me know!
Chad Erickson
Switch Product Support Engineer
NI - USA
Attachments:
synchronous scanning.JPG ‏136 KB

Similar Messages

Multiple channels switch scanning DMM

Hi,
I am using DMM (NI PXI 4071) and switch (NI TB 2627). I want to do the measurement by scanning one channel then start to measure, after that go to another channel and start to measure again (so called syncronous).
But, I have problem in my code to display the output of each channel. I just can show the output of channel 0 only.
Here I attach my code. Instead of displaying the output of the channels, actually it only can show the output of channel 0 according to how many samples that I want. That's why I try so hard to show output of others channels.
anyone can help?
Thank you for your help.=)
Sorry my code is very messy.
Solved!
Go to Solution.
Attachments:
try.vi ‏144 KB

Thanks for the response.=)
Yeah... that's my bad.. I just notice that mistake.
But actually I have change the code to become like this. (see attachment)
I'm pretty sure that if I can handle the error, then I can see the output of each channels based on the physical channel that I want.
But now, I cant figure out the error. Because it keeps saying that it's channel based task only though I already follow the example how to use daqmx create channel and daqmx read.
Attachments:
try6.vi ‏196 KB
ERROR.JPG ‏117 KB

How to set scan rate with NI Switch scan voltages

Hi
I have SCXI 1130 switch and NI 4070 DMM . I have connected 3 voltage channels on the SCXI .
When I read just one channel at one time, I get correct voltage reading. here I gave scan input as ch0->com0.
Later , i placed a For loop in the block diagram and programmatically wired the scan channel input,
for the switch and read the voltage output from the DMM, i do not get the correct outputs.
That is , for my 3 channels, i gave For loop iteration count as 3 and ,'i ' is taken and appended for ch i ->com0. the DMM measurement is not proper. But if I highlight execution in the block diagram ( if i put the bulb and the probe), i can see the correct output voltages coming out. The moment, i turn off the execute high light, the program gives incorrect output. So do I have to give a scan dealy or what time has to be set to get correct values. I am using software trigger in the bloack diagram.

Hi Hema,
CJC is an acronym for Cold-Junction Compensation, and this value adjusts for the change in voltage caused by the thermocouple wire to copper wire junction.
For example, a J-type thermocouple will have thermocouple wire consisting of iron and constantan metals. When these iron and constantan metals meet the copper at the switch connection, a difference in voltage results. This difference in voltage is the "cold-junction". The difference in voltage resulting from the iron and constantan connection in the thermocouple is the "hot-junction". When you measure temperature using a thermocouple, what you desire is the "hot-junction" change in voltage. Unfortunately, the DMM is going to measure the sum of both the "cold" and "hot" junctions, and a CJC measurement is needed so we can adjust the measurement to remove the undesired offset.
Once Cold-Junction Compensation is performed, converting from voltage to temperature is fairly simple. Each thermocouple type has its own temperature to voltage conversion equation and associated coefficients. Here's a great resource for the equations, coefficients, and specific voltage to temperature tables:
NIST ITS-90 Thermocouple Database
http://srdata.nist.gov/its90/main/
Hope this helps!
Chad Erickson
Switch Product Support Engineer
NI - USA

Keep switch channel selected for multiple steps in a scan list

Hi,
I have 3 switches (PXI-2575), one to apply a source to a given line, one to apply a sink, a one to apply a DMM. I have all three switches triggering off each other as well as a DMM (PXI-4070). I apply a source to any given line with the source switch and then cycle through other lines using the DMM switch. Problem is i want to keep the wear on the relays of the source switch to a minimum (for each cycle through the DMM lines I'm selecting same source pin multiple times!). Is there a command for scan lists or some way of setting up the switches so that this can be done?
I thought it might be possible to use the debounce command ';' on its own to signify that i don't want to change the channel selection but this does not appear to work, the DMM times out whilst waiting for a trigger on the second reading. Simplified example scan list that i currently have:
Break Mode: No Action
Source Switch: ch0->com;;;;~ch0->com & ch1->com...
DMM Switch: ch100->com;~ch100->com & ch101->com;~ch101->com & ch102->com;~ch102->com & ch103->com;~ch103->com & ch100->com...
I've also tried selecting the same channel in subsquent scan list entries which flags up error saying explicit connection already exists between the channels.
So is the only possibility just to needlessly wear out the relays?!

Hi leon007,
I can understand your desire to keep the wear on the relays of the Source switch to a minimum. I have a few questions, but we should be able to get the application working without needlessly wearing out the relays.
1. Can I assume you are using NI-SWITCH to program this application? If you are using the NI-DAQmx Switch API, please let me know.
2. When you state "I have all three switches triggering off each other as well as a DMM", can I assume (leaving out the Sink switch for now) the scan advanced output of the Source switch (TTL0) is sent to the trigger input of the DMM switch (TTL0), the scan advanced output of the DMM switch (TTL1) is sent to the trigger source of the DMM (TTL1), and the measurement complete destination of the DMM (TTL2) is sent to the trigger input of the Source switch (TTL2)?
3. If you are still having troubles after this post, I would like to know the following so I can assist in testing the issue: What versions of NI-DAQmx and NI-SWITCH do you have installed?
OK, that's it for my questions. Now for yours. Unfortunately, the debounce command ';' didn't work because it is simply a dummy entry - without creating a connection no scan advanced signal will be sent. I've noticed this is not documented well in our help file, and I apologize for that. However, attempting to create a connection where one already exists should be an error. Either the user is attempting to redundantly connect channels (which shouldn't happen if niSwitch Get Relay Position is used), or there is a driver issue.
To keep the relay wear to a minimum, I want to suggest a couple of ideas.
1. Use only one trigger line for the DMM's measurement complete and one trigger line for all the switches scan advanced outputs. To use this option, it cannot matter in your application which switch operates first, and which operates last. The switch that always makes a connection (the DMM switch) will send a scan advanced output trigger with a set scan delay (configured in niSwitch Configure Scan Trigger) that should accommodate for all the switches. This option may add delay in your application, but you will save relay life.
2. Use the DAQmx Switch API and the '&&' command between seperate switch connections. In the DAQmx Switch API, you use just one scan list for all switch modules. For example, we would perform the example scan list entries you provided with the following scan list:
/Source/ch0->com && /DMM Switch/ch100->com; ~/DMM Switch/ch100->com & /DMM Switch/ch101->com; ~/DMM Switch/ch101->com & /DMM Switch/ch102->com; ~/DMM Switch/ch102->com & /DMM Switch/ch103->com; ~/Source/ch0->com & /Source/ch1->com && ~/DMM Switch/ch103->com & /DMM Switch/ch100->com...
The above connects the Source switch CH0 to COM, waits for the relays to settle, connects the DMM switch CH100 to COM, sends the scan advanced output signal, and waits for the trigger input before executing the next scan list entry. This method will keep an order to the madness, as you will have the power to decide which switch operates first, and which operates last.
Let me know if I assumed anything incorrectly or if neither option works for you!
Chad Erickson
Switch Product Support Engineer
NI - USA

Trying to measure voltage through SCXI-1127/1331 2-wire connection [ Edited ]

Hai ,
     this is madhava from LSU,I am working on ERT with NI hardwares like 1)chasis 1000 2) DMM PCI-4060 3) SCXI -1331(2 in number)
I have a system with two large glass plates standing vertically and placed parallel to the user.I am trying to flow different liquids of density through the channel in between.Please see a attached picture of it.
    There are total of 48 electrodes 24 on each side to which wires are connected. On each side there are 3 rows with 8 electrodes/row, say 1-24 on side A and 24-48 on side B. The medium between the two sides is salt water.
     I want to measure the potential in such a manner that I can calculate the voltage difference between all possible electrode combinations between side A and side B.I have connected a two end power source to side A and side B, i.e. +ve to side A and -Ve to side B , so   the electrode on the A side acts as the "source" and the electrode on the B side acts as "sink".
    I want to use 2 SCXI- 1331 's for this experiment.
    I tried it with 1 SCXI - 1331, but did not get proper values.So what do you suggest shall I continue this with the 1 wire or could you please help me with the two wire experiment, so that I can get more combinations.
           I hope you respond soon and in the affirmative.
With regards
Madhava
Attachments:
Scanning_of_SCXI-1331_48_write.vi ‏144 KB

Welcome to the discussion forums, Madhava!
The optimal solution is to have a 2x48 (or more) matrix so
that you could easily choose one point on either plate (column) connected to
one lead of the DMM (row0) and another point on the other DMM lead (row1).
Since the SCXI-1127 doesn’t support this configuration, you’ll have to try
something else with your existing hardware.
Because you can only use a multiplexer setup instead of a
matrix for your number of signals, the closest you can get to the above
suggestion is to measure one electrode to ground and then read the next
electrode to ground and include logic to find the difference between the two voltages.
I suggest you start with a LabVIEW shipping example (Help » Find Examples) such as niSwitch
DMM Switch Synchronous Scanning.vi or niSwitch
DMM Switch Handshaking.vi (found under Hardware
Input and Output » Modular Instruments » NI-SWITCH). You will have to modify
it to include another SCXI-1127 and set them both up in a 1-wire 64x1 multiplexer
topology. Take measurements as quickly to each other as possible on both
switches. Again, this is a workaround to what you really should be doing for
optimal performance (and the easiest setup).
The last option is to limit your measurements to electrodes
directly across from each other (or any other fixed mapping setup) and use a
2-wire 32x1 multiplexer topology. By nature, this is taking a differential
signal measurement between two constant points. This would allow you to easily
use LabVIEW’s shipping examples without modification.
I hope this helps you get a feel for your options and the
consequences of each.
Mark E.
Precision DC Product Support Engineer
National Instruments
Digital Multimeters (DMMs) and LCR Meters
Programmable Power Supplies and Source Measure Units

SCXI-1127 problems

We are using a SCXI-1127 module, a NI-1331 terminal block, and a NI-1000 chassis. I set up the chassis and module correctly and wired up for 4 wire resistance measurements. I Connected the signal to channel 0A and 0B for 4 wire measurements. When i go to test, i can't get any measurements. Under the properties for the 1127 we have it set up for 4 wire mode on channels 0-15. We tried to make a virtual channel then run the tests on that channel and can't get any resistance measurements. Any ideas what could be going on here?

Hello Leonard,
First of all I would like to make sure you are connecting your signals correctly.
In the NI Switches Help (April 2003), go to the chapter "NI Switches Help >> Device Overview >> NI SCXI-1127/1128 >> 4-Wire 16x1 Multiplexer Topology". It shows there how to connect your signals and it says "In 4-wire mode, connect your excitation or source leads to xA+ and xA- and your measurement or sensing leads to xB+ and xB-".
Question 1: Are you connecting the excitation signal to 0A+ and 0A-, and the resistance legs to 0B+ and0B-?
Question 2: Use the example program "niSwitch Making Connections on a Switch.vi" in LabVIEW that s
hips with the NI-SWITCH 2.0 (or later) driver to choose the appropriate topology and to connect CH0 to COM0. If you measure in your terminal block the pins that correspond to OUT0 and OUT2, can you see the appropriate signals?
Question 3: What device are you using to measure signals from the switch? The NI 4070 DMM? Another NI DMM? If so, connect AB0 to OUTo and AB2 to OUT2 and try to get the readings in the DMM from the backplane of the chassis (see Switches Help for more information).
Question 4: How are you creating a Virtual Channel?
Talk to you later,
Claudia Lorente
Applications Engineer
National Instruments
http://www.ni.com/ask

RDA with SCXI-1127

I have an PXI-1010 chassis with a NI-4060 DMM in slot 8 and a SCXI-1127 in
slot 4. The SCXI is controled through the internal bus. I am wondering how
I can control the SCXI-1127 with NI-SWITCH from a remote computer through
RDA(Remote Device Access).

Hello;
To have a RDA process running, you need first to start the RDA server at the machine that has the hardware (go to Start->Programs->National Instruments->NI-DAQ->Remote Device Access Server). Then, create the virtual channels you want to monitor remotely.
At the remote machine, go to MAX, right click at Devices and Interfaces, select create new, and select the RDA/Ethernet Device. After you configure the IP address to be the address of the remote machine, you should be able to access all the remote virtual channels.
Hope this helps.
Filipe

Low level control of SCXI 1127 relays

Hi,
How can I close or open switches HLSELECT and 1WIRE of SCXI-1127 manually? There is a VI(1WireINDEP) which uses CIN to activate these switches. This VI allows to activate HLSELECT and 1WIRE relays when the SCXI 1127/1128 is used in 1 wire mode as a 64x1 multiplexer. The 1WIRE relay will always connect to 1wirelowref signal. The HLSELECT will connect to Com0+ when H-L Channels is set to Channels 0-31 and to Com0- when H-L Channels is set to Channels 32-63.
I need to control 1WIRE relay just like this VI controls HLSELECT relay. I have attached this VI. Can you please modfiy it or write a different VI to allow controlling 1WIRE relay. I should be able to open and close these two relays (HLSELECT and 1WIRE) manually thro
ugh the VI. If this is not possible, can we modify this VI so that the 1WIRE relay will always connect to com0- signal instead of 1wirelowref signal.
Thanks
Attachments:
1wireINDEP.vi ‏48 KB

Thanks for your reply. My problem is not that simple.I am using NI-SWITCH1.6 and need to continue using it. Can't I just use this VI as sub VI and call it? Here is my problem:
I am building a system to test cables that are open at both ends. A cable can have 4, 6, 8, 10, or 20 wires in it. I wish to test the resistance of each individual wire in a cable and insulation between wires. I have four SCXI 1127 modules with SCXI -1331 in a SCXI 1000 chassis. The switches are controlled by a PCI-4060 DMM.
I have written a VI ( in Labview 6.1, NI-SWITCH 1.6, NI DMM 1.6), which configures DMM for multipoint measurement and SCXI 1127 modules in scanner mode. I connect 1_WIRE_LOW_REF of all SCXI-1331s to a common point, which connects all wires in a cab
le/s under test. So, by using SCXI in scanner mode and generating scanlist, I can measure the resistance of individual wires. I use 1127 in 64 x1 multiplexer mode. This takes care of one requirement.
Now for insulation testing, I keep all wires of cables connected to switch channels and need to connect them in combinations. I can generate the combinations and pass it in a loop to close or open switches. I need help in creating correct paths and route the measurements to DMM.
For example:
Let�s say, we have a four wire cable, I need to test the insulation between them in pairs. There are six possible combinations: 1-2, 1-3, 1-4, 2-3, 2-4, 3-4. Let�s say these wire are connected to ch0, ch32, ch1, ch33 of module 4, the VI may need to close the switches as per the paths required (attached in word document).
I just don't know how can it be done.
Attachments:
Channel_combinations.doc ‏41 KB

SCXI 1127 4-wire software setup

Hi All
I experienced a problem to connect channel ab0 and ab2 to the respective measurement channel so that I can get a resistance reading. I'm using SCXI-1127 with 1331 and a DMM of HP34401A.
I have done my wiring correctly and now it's a matter of coding it correctly. There are lots of way to do this in my mind. Tried each one of them and didn't work.
Any help (software or detail of coding sequence) will be very much appreciated.
David Ng

- Use the chassis created in DAQmx.
- In MAX (SCXI-1127 property) select the SCXI-1331 as the terminal block for the SCXI-1127.
- Use the shiping NI-SWITCH example found in: F:\Program Files\National Instruments\LabVIEW 7.1\examples\instr\niSwitch called niSwitch Making Connection on a Switch.vi.
- Delete the second connect vi and wait for debounce
- Point to your SCXI-1127 (SC1Mod4 for example)
- Change the topology to "1127/4-Wire 16x1 Mux"
- Check the NI-SWITCH help file (Start>>Programs>>National Instruments>>NI-SWITCH>>Documentation>>NI Switches help) for valid channel names under: NI Switch Help>>Devices>>SCXI-1127/1128>>4-wire 16x1 Topology

Trying to measure voltage through SCXI-1127/1331 1-wire connection

We have NI hardwares like: 1) Chasis SCXI-1000, 2) DMM PCI- 4060, 3) MUX SCXI-1127 and 4) Terminal Block SCXI-1331
We have a system with two large glass plates standing vertically and placed parallel to each other each having 24 electrodes on them. Distance between them is 4-5 inches. The plates are places in such a way that the electrodes are on the outer side and accessible to the user. We are trying to flow different liquids of different density through the channel in between. Please find attached a picture of it.
So a total of 48 electrodes and hence, wires are connected, 24 on both sides. On each side there are 3 rows with 8 electrodes/row, making a total of 24 wires. Wire#1-24 are on side A (say) and wire# 25-48 are on side B (the other side). The medium between the two sides will be salted water (say for now).
We want to measure potential/voltage in such a manner so that we can calculate the voltage difference between all possible electrode combinations between side A and side B. Like V1-25, V1-26, V1-27,...,V1-48,V2-25,V2-26,........,V24-48, all 24 X 24 possible combinations. We are connecting two end of a power source to side A and side B so that there is some current flowing in the water.
I have connected wire# 1-48 to 1-48 in SCXI 1331 (left out the zero to avoid confusion). Now that I'm measuring values through the program attached ("Scanning_....vi"), I can see that the first 16 values are showing some values of standards E-2. But from 17-48 are showing values of standard 5E-3 and I guess they are not taking any values at all. Can you tell me why this might be happenning?
Can 1-wire measurement be applied for this scenario. If not then let me know how to achieve our goal. I can manually take a Multimeter and measure all the combinations one by one, but measuring all the values at the same instance would be better and that only can be done by automation and I hope that the NI hardwares I have, should be sufficient to do that. Please let me know if it is otherwise.
Another thing, in one of my previous contact with NI someone mentioned connecting 1_WIRE_LO_REF. Is it needed in this case? If yes, then if I connect one end to 1_WIRE_LO_REF, where should I put the other end?
In case the program is wrong or more than 16 values can not be taken please let me know alternate path or show me how to make changes in the program. I would appreciate your help in this issue. Thank you.
Message Edited by ERT_LSU on 09-17-2007 12:16 PM
Attachments:
Scanning_of_SCXI-1127_48_write.vi ‏144 KB
IM0000021.jpg ‏767 KB
IM0000041.jpg ‏722 KB

I connected the COM of my power source to the 1_WIRE_LO_REF. There are 4-5 points to connect. I choose the middle slot. Is there any significance of assigning so many slots to 1_WIRE_LO_REF?
No change in result. Can you please test run the program I attached and see whether it's correct or not. You'll see 48 segments getting the output. First 16 of them are showing some seemingly proper values. rset are either too small or as big as 5 V.
I'm providing 5Vs from the power source. You might have seen the old analog ones. I'm using one of them. there are different Voltgae option. I'm using the 5V and so I've connected a wire from the 5V connection to one of the electrodes on B side (28th electrode) and the COM ports goes to the A side (4th electrode) and also to 1_WIRE_LO_REF.
Now I'm thinking if the program if not working. Because it seems that we are getting (seemingly) proper values for the first sixteen and something's messing up the values for the the rest of the electrodes.
Do I have to use two 24X1 MUXs i.e, use physically different boards and also two different programs to measure them? Or I can just use 1-24 as 24X1 and 25-48 as another 24X1 in the same board and measure them through the same program? Thanks in advance.
Message Edited by ERT_LSU on 09-17-2007 04:00 PM

SCXI-1127 and Reset NISwitch VI

I have a question with regard to resetting the SCXI-1127 Card.
I wrote a test VI that performs the following in sequence to
verify the -1127 operation:
1) Initialize the SCXI-1127 Card
(using a Instrument Descriptor of SCXI1::5::INDEP)
2) Control a single Switch (Close ch0)
3) Close the NI Switch Reference
The switch closes correctly, because I can hear it, but here is
the kicker, if I put the entire 3 steps in a While loop controlled
by a Boolean stop switch and run the VI, the Switch chatters (its
being opened and closed continuously). Now I realize that this is
normal operation *IF* the Initialize NISwitch VI is performing a reset
of all of the switches (i.e. OPENING all switches). However, I am
setting the ResetDevi
ce Input Boolean to False when I call the
Initialize NI switch VI, but it appears that the board is resetting
anyway. Has anyone seem this before? or is the Reset Device input
on the Initialize NISwitch VI not what it appears to be to me?
(The reason I am attempting this is to assertain that I *can* call
initialize (to get a reference) without changing the current state of
the switches. this is because I am leaving the LabVIEW environment
between switch setup calls, therefore I need to close the open
Instrument reference)
Any Help would be appreciated
Rick M
Sent via Deja.com http://www.deja.com/
Before you buy.

Rick,
you are right: the reset option in this moment is not yet performing any
action inside the NI Switch driver. We apologize for the inconvenience: it
will be activated in future release of the products. Unfortunately, in this
moment it is not possible to avoid the RESET of the switch card when you
open a new session.
Maurizio
[email protected] wrote:
>I have a question with regard to resetting the SCXI-1127 Card.>I wrote a
test VI that performs the following in sequence to>verify the -1127 operation>1)
Initialize the SCXI-1127 Card>(using a Instrument Descriptor of SCXI1::5::INDEP)>>2)
Control a single Switch (Close ch0)>>3) Close the NI Switch Reference>>The
switch closes correctly, because I can hear it, but here is>the kicker, if
I put the entire 3
steps in a While loop controlled>by a Boolean stop switch
and run the VI, the Switch chatters (its>being opened and closed continuously).
Now I realize that this is>normal operation *IF* the Initialize NISwitch
VI is performing a reset>of all of the switches (i.e. OPENING all switches).
However, I am>setting the ResetDevice Input Boolean to False when I call
the>Initialize NI switch VI, but it appears that the board is resetting>anyway.
Has anyone seem this before? or is the Reset Device input>on the Initialize
NISwitch VI not what it appears to be to me?>>(The reason I am attempting
this is to assertain that I *can* call>initialize (to get a reference) without
changing the current state of>the switches. this is because I am leaving
the LabVIEW environment>between switch setup calls, therefore I need to close
the open>Instrument reference)>>Any Help would be appreciated>Rick M>>>Sent
via Deja.com http://www.deja.com/>Before you buy.

Mercury Relay Contact Resistance using SCXI 1127

I am trying to measure Resistance on PWBA with Mercury Relays using SCXI 1127, 1331 connector block and DMM 4060. I am using 2 wire mode. The Mercury Relays have 0.25 Ohm contact resistance. The readings measurements fluctuates and are high measuring from 0.7 to 1.5 ohms. I would like to know what is the contact resistance of SCXI 1127 Relays and any suggestion to improve measurements. Why the measurements fluctuates every time. Do you think any common grounding considerations or programming changes can be done to improve. Any suggetions ? Thanks.

Looks like this message is a duplicate. For those looking for the answer, please follow the other discussion thread at the link below:
http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=135&HOID=506500000008000000AF3E0000&USEARCHCONTEXT_CATEGORY_0=_200_&USEARCHCONTEXT_CATEGORY_S=0&UCATEGORY_0=_200_&UCATEGORY_S=0

2.5MHz oscillations on scxi-1127 AI channels

I'm trying to measure the circuit below through a SCXI-1127 multiplexer and I'm seeing a 2.5MHZ sinusoid when I connect my circuit output to the multiplexer. Alone, I don't see this signal, but as soon as I connect to the mux input, it pops up and it is very large. I can see this signal not only in my software but with an O'scope probe across the circuit's output. The circuit is a simple Inverting amp and I'm using LT1212 op amp. I'm also using a virtual ground between the rails since I'm running on battery. When connected to other DAQ's or Oscilloscope, I get a clean signal, but when connected to SCXI-1127, it shows up - even when the switch isn't on. Any suggestions or ideas of what the cause might be?

Classical event: Amplifier oscillate, while oscillators won't
How much bandwidht do you need?
A small cap (5-100p) in the feedback loop and a 10R right after the OP output help
The reason for the oscillation is the higher capacitive load.
Greetings from Germany
Henrik
LV since v3.1
“ground” is a convenient fantasy
'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'

SCXI--1127 relay banks layout

When using the SCXI-1127 in the 2 wire mode configuration, will it be using only the 32 relays located in the left bank of the PCB?
I am trying to measure the path resistance in this configuration, but I need to identify the relays used in this configuration. The PCB has a total of 45 relays distributed in two banks, can you confirm with me that only the 32 on the left bank are being used in the 2 wire mode configuration?

Hi maggan,
To answer this specific question and related inquiries, I strongly recommend the NI Switches Help (installed with the NI-SWITCH driver). Download the Help by itself using the following link:
NI Switches Help
http://digital.ni.com/manuals.nsf/websearch/B133DDD29F0DFCC28625746E00564E56
The relay replacement section is a great resource for information such as which relays are used to connect a particular channel to COM. In the attached picture, I've outlined the relays used to connect ch0 to com0 in the SCXI-1127's inherent 2-Wire 32x1 Multiplexer Topology.
Let me know if you have further questions!
Chad Erickson
Switch Product Support Engineer
NI - USA
Message Edited by Chad PSE on 02-17-2009 11:39 AM
Attachments:
1127 2-wire - ch0 to com0.JPG ‏121 KB

Null offset DMM 4070

Hi
How to programm the null offset in C# using the class library from the DMM4070
I want to use the "null offset" from the DMM 4070 softfront pannel in my programm but i can't find a method for it
Thanks in advance
tonnie

Hello Tonnie,
I had misunderstood your request clearly.
I thought you were looking for more information into specific types of "automated" offset nulling.
If you just want to implement the offset nulling checkmark behavior, then you can do this quite easy.
I thought you had already seen this by going to the Soft Front Panel its help.
The functionality of this checkmark/button is quite simple (taken from the help):
"Null Offset stores the current reading of the DMM and subtracts it from any future readings. The stored offset is shown on the display. When enabled, the Null Offset value is updated if the device, function, or range is changed."
So basically this just comes down to defining a button or checkmark that:
1 Stores the current actual reading (without this software based offset nulling) in a variable x at the moment when your button goes from "disabled" to "enabled" state. (eg. moving a switch from off to on)
2 While this is enabled you will subtract your offset from any current reading as a sort of very simple software post-processing. (eg. switch still in on-position)
3 When you go back from the enabled state to the disabled state, you reset the variable x to zero/0 value (eg. switch from on to off)
4 When you are in disabled state (eg. off-position of your switch) , then you just read the actual readings + your variable x (=0).
This comes down to just reading the actual reading (without the software based zero offset.
5 You will wait until you again go from the disabled to the enabled state. If this happens, then do step 1 again.
So basically, you just need to add an offset value to your actual reading and set this offset value when you do a transition of disabled to enabled state or from enabled state to disabled state.
Kind Regards,
Thierry C - Applications Engineering Specialist Northern European Region - National Instruments
CLD, CTA
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Multiple scxi 1127 switches scanning, dmm 4070

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