What Block (function) is this?

[GJMABerends]

Ok, now you actualy measure what the sensor gives back at you at the least one of the two channels. Usually an LVDT has two outputs and a reference input. Does your sensor has the following configuration? :

Version:1.0 StartHTML:000000243 EndHTML:000043287 StartFragment:000043023 EndFragment:000043219 StartSelection:000043023 EndSelection:000043219 SourceURL:http://www.te.com/usa-en/industries/sensor-solutions/insights/lvdt-tutorial.html LVDT Tutorial | LVDT Basics - What is an LVDT | TE Connectivity

So you should have an S1, S2, and a P at your sensor. Based on your specification check if the sensor is connected correctly.

[alaspina]

Gert-Jan,

Well, it is reading, but an LVDT sensor is not supposed be used my making contact with the inner loop as far as I know. 

I believe it does have the same configuration. I attached a schematic from the info sheet (HR 100 LVDT). 

I can't really say if it is connected correctly, it has 6 wires coming out from a black tape wrapped at the end- this was a previous colleague's work. 

I don't think I've mentioned it, but all 6 of these wires run through a circuit board, that has an AD598 chip, essentially an amplifier. Whilst I originally thought that I needed an external voltage source, from the AD598 info sheet it seems that this is its external excitation source for the LVDT. 

[alaspina]

Gert-Jan, 

It has 5 wires, not 6. I also cannot tell which wire directly leads to the DAQ because there is an adapter to the circuit that passes 5 wires from the LVDT and 4 set of wires to the DAQ card. I have both the digital and analog line of pins grounded with one wire each. The rest are connected to the AO analog pin and the 2.5 V Digital pin. 

[GJMABerends]

Alaspina,

5 wires seem normal. The AD598 needs a powersupply between Pin 1 and Pin 20. Can you measure with a voltage meter that it actualy has a powersupply? If so measure between pin 2 and 3 if you can measure the excitation (AC Voltage) signal going to the sensor? If there is no powersupply than you should check if the pcb has a power supply. If there is no excitation signal than the chip is death.

If it has a powersupply and there is an excitation signal can can you measure between pin 17 and 10 also a AC voltage? If not then you sensor is either defective or not mounted properly. 

I am assuming that the setup has worked in the past and doesn't any more. But for now lets check our basics first and make sure that everything works

[LV_Pro]

I would suggest going back one more step, use NI Measurement & Automation Explorer (MAX). Create a Task; Acquire Signals/Analog Input/Position/LVDT to see if: 1) you have a device that is LVDT capable, 2) It is getting signals. I usually do this first, before trying to troubleshoot my code, has shown me errors in wiring, dead devices, etc., before trying to determine why LabVIEW code isn't working.

[GJMABerends]

LV_Pro

That is what we are doing ever since we detected that we did not get the expected signals.

[alaspina]

LV_Pro, 

My LVDT device cannot be directly read from the Analog input-> Position-> LVDT sensor option. The only way it can be read (incorrectly) is with the voltage input. 

Gert-Jan, 

Can the DAQ card recognize voltage inputs from any pin? What are the 2.5 and 5 V inputs on the digital side for then? 

[GerdW]

Hi alaspina,

Can the DAQ card recognize voltage inputs from any pin?

Your USB6009 can read voltage signals on any analog input.

What are the 2.5 and 5 V inputs on the digital side for then? 

Those are no inputs, they are outputs - as is written in the manual of your device!

RTFM!

[GJMABerends]

Alaspina

GerdW is correct, the 2.5 and 5 volt connections on pin 30 and 31 are Analog outputs. Based on the specs of the USB-6009 the inputs you could use are:

AI0 = pin 2

AI1 = pin 3

AI2 = pin 5

AI3 = pin 6

AI4 = pin 8

AI5 = pin 9

AI6 = pin 11

AI7 = pin 12

They measure voltages related to

GND = Pin 1/4/7/10/13/16

Please confirm that you connected the sensor correctly to the DAQ device.

[LV_Pro]

Gert-Jan

    Sorry, I didn't see any where that you had suggested just using MAX to see the signals, only that you had a simplified DAQ program.