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Help with niSwitch DMM Switch Handshaking example

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I'm having a bit of trouble getting my PXI-2575 Relay Multiplexer and PXI-4071 DMM to talk to each other.  They are located in a PXI-1045 chassis on which I am running the "niSwitch DMM Switch Handshaking.vi" example.


At the moment all I am trying to do is read in a DC voltage using this example.



Topology: 2575/1-Wire 196x1 Mux

Scan list: ch0->com;

Trigger input: Front Connector

Scan advanced output: Front Connector



Measurement type: DC Volts


Measurement complete destination: External

Trigger source: External


When attempt to run the VI, I get the following error:


Possible reason(s):
Driver Status:  (Hex 0xBFFA6B9F) DAQmx Error -89120 occurred:
Source terminal to be routed could not be found on the device.

Make sure the terminal name is valid for the specified device. Refer to Measurement & Automation Explorer for valid terminal names.

Property: DAQmx_DigEdge_AdvTrig_Src
Property: DAQmx_DigEdge_AdvTrig_Edge
Source Device: PXI1Slot7
Source Terminal: TrigIn

Status Code: -89120


Obviously, I am new at this.  Please help!


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Message 1 of 11

Hi Sean,

        I believe that the error your getting is because the driver wants a different input than "front connector" for the trigger line of the switch.  Which trigger lines are you connecting through on your terminal block?  I'd recommend changing those inputs to to TTLX (X being whichever line you're connected to).  Having "external" for your DMM selections should be just fine.  Let me know if changing those inputs doesn't help!


Applications Engineer
National Instruments

Digital Multimeters
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Message 2 of 11

Hi Anita, thanks for the reply.


Two things:

1)  Unfortunately I do not have access to a 50-pin terminal block yet (I believe it's on order), so just to get familiar with the hardware I've been connecting two wires from my intended measurement location (2VDC) to lines 0 and 1 to the PXI-2575 (through my LFH200 cable).  I have been attempting to measure this with the example to no avail.


2) Changing the Switch input/output to TTL0/TTL1 causes the following error:


"Error -1074126845 occurred at niDMM Fetch Multi Point.vi -  Possible reason(s): Max Time exceeded before operation completed"


And I see four samples were taken and displaced on the accompanying graph.


Do you know what I'm doing wrong?




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Message 3 of 11

Hey Sean,

While many of our switch modules have front panel triggers, the 2575 does not, so we'll need to use the TTL lines as Anita mentioned previously.  These TTL lines route via the back connector on the DMM and the Switch module, so no external trigger wiring is needed.  Here's a screenshot of one TTL routing solution:




This should get you clicking 'til the cows come home.


If the above doesn't work, post back with card placement in your chassis and we'll advise.

-John Sullivan
Problem Solver
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Message 4 of 11

Hi Knights Who Say Ni,

(great name!)

I set up my example exactly as you did and ran it, and again I got the same "Max Time Exceeded" error I saw before:

"Error -1074126845 occurred at niDMM Fetch Multi Point.vi -  Possible reason(s): Max Time exceeded before operation completed"


 My DMM (PXI-4071) is located in Slot 2 and my switch is located in Slot 7.  Slots 3 through 6 are available with identical switches if you think changing to one of them would help.


Also, to measure 2 DC Volts I'm running a wire from my source to line 0 and GND to line 1...is that correct?




Edit:  I went ahead and tried the PXI-2575 switch in Slot 3 and as you said it got me clickin' away.  Can you explain to me the difference?

Message Edited by SeanB_1 on 01-25-2010 01:16 PM
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Message 5 of 11

Hey Sean,


Some chassis have multiple segments that don't share triggers by default.  To see if your chassis has multiple segments, let's put the switch in slot 6, as this will place both the DMM and the Switch in the same segment of the chassis.  If everything works fine, we need to setup trigger routing between segments in MAX.  I'll let Anita elaborate on this and on the connection procedure, but this'll get you up and running today.

-John Sullivan
Problem Solver
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Message 6 of 11



So I am up and running as far as switching goes.  However I am apparently doing something wrong when I try pass the signal from the switch to the DMM as I am not able to measure anything I put on ch0 or ch1.  I will play around with MAX and see if I can get it working while I wait for Anita to respond.  Thank you very much!


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Message 7 of 11

Hey Sean,


Let us know your circuit diagram and we'll see why you aren't getting the readings you want. Also, let us know the topology you're using on the 2575 (1-wire 196x1, 2-wire 95x1, or 2-wire 98x1).  

Message Edited by Knights Who Say NI on 01-25-2010 03:58 PM
-John Sullivan
Problem Solver
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Message 8 of 11
It is in process of being designed for my application, so at the moment I'm just using a power supply supplying 2VDC to ch0 and ch1 (GND).  I have not settled on a topology yet and have tried using all three to getting the measurements working.  I will be measuring both DC Voltage/Current as well as Resistance so I was leaning towards either of the 2-wire topologies.
It seems like such a basic setup but I am unsure of what is keeping me from making measurements with my DMM.  I have no problems utilizing the front banana plug connectors to measure what I want, but having the switch route the signals to the DMM and have it measure them is giving me trouble.
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Message 9 of 11
Accepted by SeanB_1

Hey Sean,


It sounds like we have a 2 volt differential signal. Let's use 2-wire 98x1 and make the following connections:


From the switches help:



From this, we can see in the bottom right corner that CH0+ is pin 1 and CH0- is pin 2.  We should hook up the 2 volt signal to pin 1 and the ground to pin 2.  


We should hook up the DMM HI to COM+ (pin 173) and the DMM Lo to COM- (pin 174).


Now all we need to do is open Switch Soft Sront Panel (Start»Programs»National Instruments»NI-Switch), select out topology (2-wire 98x1) and connect CH0 to Com.  If we take a DMM measurement, we should now read 2 volts. 


Now that we've got everything working, let's make it faster using the handshaking example you mentioned previously:

Suppose we want to connect channel 0 to com, take a measurement, then connect channel 1 to com, take a measurement, then connect channel 2 to com, etc... all the way up to channel 15 to com.  A scan list that accomplishes this is: "ch0->com; ch1->com; ch2->com; ch3->com; ch4->com; ch5->com; ch6->com; ch7->com; ch8->com; ch9->com; ch10->com; ch11->com; ch12->com; ch13->com; ch14->com; ch15->com;".


We can simplify this scan list using the ':', as follows: ch0:15->com.  This equates to the same actions as above, but is much simpler to look at.  Hopefully this is enough information to get started.  Let us know if you have any questions.  Have a great day!

Message Edited by Knights Who Say NI on 01-25-2010 05:05 PM
-John Sullivan
Problem Solver
Message 10 of 11