Simulated devices

[Driga]

I need to simulated the following hardware:

1. Chassis: SCXI-1000 with, SCXI-1600

2. Module: SCXI-1102, SCXI-1581, and SCXI-1102C

3. Terminal block: SCXI-1300

Most likely, I will use the above hardwares. However, those hardwares are being used at the moment. I am new in doing creating virtual instrument for measurement. And I would like to start by simulating the devices. Then work my way on how to read the signal, process it and display it.

My objective is to measure the flow rate. The sensor's output signal is pulses with value of 319 pulses/liter.

First how to simulated the above devices? I did try the following.

Device and Interfaces > Create New > NI-DAQmx Simulated Device > SCXI Chassis > NI SCXI-1000

I put an arbitrary address, when I chose Save it prompts me to pick communicating DAQ device.

Thanks! 

[BerndF]

Hi Driga,

the SCXi chassis/modules just do signal conditioning, but no aquisition.Therefore you have to connect the SCXi chassis to a data aquisition board.

As you try to simulate the setup, you have to include a simulated  DAQ-device and a simulated SCXI chassis.

To do so, open up Measurement & Automation Explorer (MAX for short), expand Devices and Interfaces, and right-click NI-DAQmx Devices, selecting Create New NI-DAQmx Device » NI-DAQmx Simulated Device.Choose an appropriate device like e.g. the PCI 6225. After that you can create the simulated SCXI chassis (what you already did). After that you have to "connect" the chassis with the (simulated) DAQ board,this can be done in the properties tab of the chassis.

Regards,
Bernd

[Driga]

Hi Bernd,

Thanks for the reply. I am quite confuse here. The hardwares which I have mentioned are not used in the same test bench. To make it clear let us say there is the old and the new one.

In the old test section, the cable from the sensor is connected into a PCB, in one of the channel and it is safely placed inside SCXI-1300. So this SCXI-1300 is not an acquisition card? Then what about PCI 6035E and NI USB 6252 ? Are they data acquisition card? Because I think PCI 6035E is used in the old test section and the latter is used in the new test section.

I will try to do based ón your answer.

One more question if my sensors ouput signal is pulses, what would be the appropriate input signal for my DAQmx?

Thanks

[Driga]

The NI USB suppose to be NI USB-6525

[BerndF]

Hi Driga,

SCXI is part of our signal conditioning products. The SCXI chassis and modules are solely used to prepare the signal for the adjacent A/D conversion which is done by the data aquisiton card. E.g. the SCXI is a thermocouple module that is responsible to amplify the signal from a thermocouple, nevertheless the output is still an analog signal.

To convert this signals to a digital signal you need an appropriate data aquisition board, the PCI 6035E is OK.

Our multifunction DAQ devices typically have an analog input range of +/- 10V, the digital inputs are TTL compatible. So when you say you want to measure pulses, the question is what you mean by "measuring": Determine the period or frequency of the signal, determine the velocity of a rotating shaft? And what's the magnitude and frequency of your pulsing signal?

Regards,
Bernd

[Driga]

I want to measure the volume flow rate using flow meter.

The technical data of the flow meter is as follow:

Pulse generator:

PNP transmitter -40... 125 °C

Auxiliary power : 10-30 Vdc

The equivalent of 1 liter is 319 pulses. 

I have no information about the frequency  and the magnitude of the signal. There are no information in the instruction manual of the flow meter.

[Driga]

O wait,

the frequency of the flow meter is 3.2 - 159 Hz

What does it mean combine with the previous information?

[BerndF]

I presume that the signal you measure equals TTL level. So in your case I assume that by counting the digital edges you can calculate the flow rate.

To get a better understanding of how SCXI works, please have a look at following documents:

SCXI Quick Start Guide

SCXI Chassis User Manual and Specifications

Getting Started with SCXI

[Driga]

Hi Bernd,

Yes, you are right. I need to count the digital events. I found an example in lv (count digital events.vi). Since I do not have any physical channel, I created virtual instrument. (NI PCI 6220).

Then use Test panels>Counter I/O and change the mode to Edge Counting. Then I click start but nothing happen on my screen. So I just close the the dialog menu. Then I run test panels again, go to counter I/O, and the mode becomes Pulse Train Generation. What is happening here?

I tried another one. This one by creating a task. Create Task>Acquire Signals>Counter Input>Edge Count then I choose the device (PCI 6220/ctr0), naming the task then finish. I choose continuous samples as the acquisition mode then selected the correct clock source on the advanced timing tab. The I saved my task.

I moved back to the vi, choose Dev1/ctr0 (PCI 6220), run the vi. After some seconds, I stopped the vi, but nothing appears on the data.

Do you have any suggestion?

Thanks.