using dmm to make readings.

[Trinity79]

I have a embedded controller pxi 8176 connecting several devices: DMM, DAQs, FG, etc. The DMM is connected to 3 SCXI 1127 modules starting on Slot 10 of a SCXI 1001 Chassis. I hooked a resistor in the terminal block in channel 9. Max see the devices. I need to make a simple resistance measurement before I can move on. Can I use a virtual channel? Also a simple example reading 5 channels would help. I'm using LV 7.0 on W2K machine. The drivers are from LV 7.1, so I can use DAQmx for the dmm.

[JasonWhite]

There are a couple of good examples that ship with DAQmx that show how to scan a switch using a DMM that should work with your 1127's. See:

Switch Scanning with DMM - Handshaking.vi
or
Switch Scanning with DMM - Synchronous.vi

These should show up in LabVIEW's example finder but you can also browse to them at:

\examples\DAQmx\Switches\switch.llb


All National Instruments DMMs are controlled programmatically through the NI-DMM API. These examples combine the usage of NI-DMM along with the calls to control your switches.

[Trinity79]

Jason,

Thanks for you answer. I tried your suggestion priorto posting this. Apparently there is some communication.

Although I am doing a 2 Resistance wire measurement (ie hook up a resistor to channel 9 of 1331 terminal block).

Running one of the programs would give me a listing of the results for 9 channels.

All of which reads a NAN. First of all, I would assume I would get NAN readings for all the channels except channel 9.

That's why I want to create a virtual channel to see if that particular channel is working, or if it is communicating with the right switch.

Any ideas what I'm doing wrong?

[SnarrVIEW]

Hi Trinity,

First off you need to make sure you have the correct cabling connected from your DMM to your switches. Please refer to Setup 5-Using SH9MD-Aux Cable in the NI-SWITCHES Help (Start -> All Programs -> National Instruments -> NI-SWITCH -> Documentation) under Programming NI Switches -> Features -> Scanning -> Scanning NI Switches with NI Digital Multimeters -> Single Module Scanning -> Synchronous. To just test different switches try using the NI-SWITCH Soft Front Panel (Start -> All Programs -> National Instruments -> NI-SWITCH). It is a great resource for troubleshooting. Let me know if this was of any help.

[Guy Ferraro]

You cannot use virtual channels with swith channels.

If you just want to read a single channel from an SCXI-1127, you can use examples that ships with NI-SWITCH and NI-DMM.
In the attached examples I combined: niSwitch Making Connection on a Switch.vi found in \Program Files\National Instruments\LabVIEW 7.0\examples\instr\niSwitch and a DMM examples Measuring Resistance (2 or 4 wire).vi found in C:\Program Files\National Instruments\LabVIEW 7.0\examples\instr\niDMM\Single Measurements.

You have to make sure you have a path from the SCXI-1127 to the DMM.
1) If you route your signal to the back of the SCXI-1127, you will need an HV8-BAN4 cable going from the back of the SCXI-1127 to the banana plugs on the front of the DMM. In the attac
hed program you will need to connect ch9 to com0 and com0 to ab0.
2) If your DMM is connected to screw terminals on the SCXI-1331 labeles OUT0+ and OUT0-, then in the attached program you only need to close ch9 to com0

For more info on signal names the NI Switches Help under Devices Overview>>SCXI-1127

If you are using the scanning examples mentionned by Jason make sure you are routing your triggers correctly so the switch advances to all the channels in the scan list. Use the references from Bryan to correctly connect your switch and DMM.
If the DMM controls the switch using the SH9MD cable the Measurement Complete from the DMM should be set to "External" and the Trigger input on the switch should be set to "rear connector"

[Trinity79]

Thanks guys,

Bryan,

I tried your solution, and check the connection. From that I know that the DMM works w/o the switch. I am pretty sure it is hooked up correctly. So the problem I believe is the the configuration of the switch. When I run the soft panel as you suggested, a error occurs: "Cannot explicitly connect to source(I think this is the term, I'm not in the lab right now.)"
Also, I have a pxi 1006 chassis: does it matter what slot the dmm is connected to? Does the SCXI 1127 have to be connected to slot 12?(Suggested in the user manual 1-9)

Guy,

I hooked up a resistor to channel 9, do I need to hook anything else in the terminal? My configuration is hooked as 1). I noticed that in the properties in max, I nee
d to set up the channels. One side is the source, and the other is for routing. Which is which?

Thanks guys. Your help is greatly appreciated.

[Guy Ferraro]

You do not need to connect anything else other than the resistor in the terminal bock. Connect the resistor to 9+ and 9- terminals. Read the "2w" line in the SCXI-1331.
You do not need to mess with source and configuration channels in your case in MAX. You can read about it in the NI Switches Help>>Programming with NI-Switch>>Features.

It does not matter where the DMM is. Put the 1127 in Slot 12 to insure that the back plane adapter connects correctly to the back of the 1127.
Do you have a HV8-BAN4 cable between the SCXI-1359 (connected to the back of the 1127) and the front of the DMM? Make sure AB0+ and AB0- are correctly connected to the DMM.
1) Open the DMM Soft Front Panel and set it to 2 wire resistance to the apr
opriate range.
2) Open the Switch Soft Front Panel and select the 1127.
3) Select the 32x1 topology.
4) Connect ch9 to com0 click on execute (you should here a click)
5) Connect com0 to ab0 (you should hear a click)
6) Look in the DMM SFP you should see the resistance of the connector on ch9.

Until this works you should not go into programming.
If it works than you can use the program I attached and connect ch9 to com0 and com0 to ab0 and read the resistance with the DMM.
If it doesn't work tell me exactly which step fails.

[Guy Ferraro]

Also make sure the 1127 with the resistor is in Slot 12.

[Trinity79]

Guy,

This is exactly what I needed. Thanks!!
Now I can finally get to the fun stuff.

Thanx everyone.