Interfacing instrument in Labview

[Fromm]

Hello,

I would like to interface a Luxtron m600 fiber optic temperature sensor so that I can use it to receive analog input signals to control heating of samples.

My obstacle is getting the FOT sensor to communicate with my desktop. In MAX, I tried configuring the NI PCI-6229 I'm using under "Devices and Interfaces" with the sensor attached to the connector block with stripped wire but could not create the task. My understanding is that since the FOT sensor is a third-party instrument, I also need to connect it to one of the serial ports of the computer by using VISA Interactive control. In addition, I also need to download the driver that is specific to the sensor.

I have downloaded the mentioned software and managed to get temperature data from the sensor using the driver. But my goal is to incorporate this data into a top-level VI that will utilize the PID toolkit. Before, I have used a USB based DAQ device and only had to use the DAQ assistance input express function to acquire signals. But for this application do I need to use both DAQ assistant and the Instrument assistant or is there a different procedure carry thought that will allow me to interface the FOT sensor with the PCI-6229? I have only been using Labview for a few weeks so detailed steps would be greatly appreciated. Thank you for your time and patience.

I have attached the driver I downloaded for reference.

[Dennis_Knutson]

As part of your homework you might want to review the basics of control loops and what a pid is. Your instrument is the feedback in the loop and is the process variable input to the pid function. The sensors are connected to the instrument correct? There would be no physical connection to the daq board. The output of the pid would control the daq board. Perhaps commanding it to generate a pwm signal. The physical connection you would make would be to the heating element.

[Fromm]

The plug-in sensor has a non-referenced single-ended connection with the connector block that connects to the daq card. In addition this same sensor is connected to the serial port of the computer. This setup comprises the input to the daq device.  The output from the daq to the heating station will also consist of a physical connection with AWG wire from the connector block.

 I've reviewed the basics of PID control but my immediate problem is with interfacing the temperature sensor. The feedback from the sensor consists of a signal comprised of voltage. This signal is conditioned by the NRSE setup in the connector block to reduced unwanted noise and then transmitted to the daq device. I will then use lab view to convert the conditioned signal to a temperature reading. However, I am unsure if I need to have the sensor connected to both the daq card via the connector block and the direct connection to the computer via the serial port. I've tried the former but the sensor will not be recognized in MAX. Currently, I am trying to interface with VISA but this has also been unsuccessful.

[Dennis_Knutson]

You are using confusing terminology. You have an instrument and sensor/probe that measures temperature, correct? This is the Luxtron that you said have been able to communicate with and read temperatures, correct? If so, then why would you attempt to connect anything from this instrument to the DAQ card? The only reason you would connect probes to the DAQ card is if you did not have the RS-232 instrument that is also reading the probe. In your proposed setup, you would have two devices reading temperature - the Luxtron and the NI DAQ card. Makes no sense to me. Since, you previously said that you were able to successfully use the driver to communicate and read temperatures, your statement about being unsuccessful with VISA makes even less sense. You can't have it both ways. The only thing you should expect to find in MAX is the com port. An specific instrument connected to a com port is not supposed to be detected.

[Fromm]

Correct. I previously made the assumption that the FOT sensor could be connected in a similar manner one would with a conventional temperature sensor such as a thermocouple or thermistor. But since the probe attaches to the sensor to measure the data that is collected, the need for a physical connection to the DAQ device will be meaningless.  In addition, the sensor to which the fiber optic probe attaches to has an analog output terminal for which I assumed meant I could use it to connect to the daq device using the NRSE setup. I thought that this analog output terminal would bypass the sensor and send the signal directly to the daq device.

As for what I mentioned before about the driver, I did manage to acquire temperature readings from the sensor using the serial port but what I want is to use labview to implement PID control in response to the process variable from the FOT sensor. The driver uses VISA to interface with the sensor but the VI block for this driver does not have terminals to which I can connect to the top-level VI. My objective is not only to acquire temperature readings but also analyze this data for PID control. My interpretation of the setup that I had previously was that the SCB-68 connector box had to connect to the sensor in order to create the VI using daq assistance. In the past, I have only worked with a USB-based daq device to collect sound using MAX and daq assist to create the VI I needed. Regardless, I will now attempt to interface with VISA. Thank you for your helpful response

[Dennis_Knutson · Accepted solution]

If you do not know how to add terminals to the connector pane in LabVIEW, you really need to start with the LabVIEW tutorial. Extremely basic task that should take no more than 60 seconds.

Throw away the instrument if you want and instead use the DAQ card to read the sensor. Makes no difference to me. You still have to hook up your DAQ card to whatever is going to be the heating element. Your reading of the temperature is only half of the setup. Since you already have this part done with the driver, I don't understand at all why you are not focusing on the output control part.