______________________________________________________________________________________________ #1 doesn't matter unless the OP is trying to measure distances dynamically, at a high rate of change, such as a fast moving robot arm. If we are measuring a stationary object - just for the purpose of getting the thing to work - the frequency response is a non-issue. _______________________________________________________________________________________________ You are correct about that. But the Laser has a limited tracking range, in order +/- 1 or 100 depending the device. I think his eventual goal iw either measurement of material going through a fix location or a frequency type measurement which would have high rate of change. You are right about the A/D device, but then to measure the low voltages, he has to be careful about the grounding, etc.. otherwise he can get a lot of noise on the device and make the measurement useless.

[Jolanta]

Hi there

I have PCIe 6321 and microtrak II Laser used for scanning.

Is there a way to convert analog voltage of a laser sensor to the corresponding distance between the laser and the object being scanned??

Thank you

Jolanta

[Broken_Arrow]

You second sentence in confusing because the Microtrak II is a distance measuring device. The information you seek should be in the literature. Are you having problems with scaling? Interfacing to the DAQ?

[Jolanta]

Yes when I used the Laser alone without the DAQ the laser software does give me the results.

But when used interfacing with the DAQ device, I am only able to get the value of the voltage, and I am not very good at converting this value to the corresponding distance between the object and the laser. 

Thanks for youe reply.

Sincerely

Jolanta

[NIquist]

The spec sheet says it has a +/- 5V voltage output AND an RS-485 Serial Interface.  You either need to know Distance per Volt conversion factor (which should be in the manual that shipped with the unit) OR just use the serial port and read the value directly.  You won't even need your DAQ card to do that so it's cheaper and easier.

[Jolanta]

They havent given any information about he distance/volt conversion factor in the user manual. I have emailed the company if they have this.

Meanwhile could you be a bit more specific about  the second option, " Use the serial port abd read the value directly."

Regards 

Jolanta

[Broken_Arrow]

An 18 second internet search told me that the Microtrak II is available in +/- 1mm to +/- 100mm. Decide which one you have. Then, for now, assume 5V = maximum range. You may have to factor in the standoff amount. Measure the voltage at Maximum Distance. What does it equal? Add the standoff amount if the value is wrong. See what you get. Reverse engineer the damn thing if you have to!  Make your own interpolation table. Scale it in software. We can help from there.

[Joseph_Loo]

You need to spec your requirements out.

1.  The device looks like a 20khz device. It implies that you will need to sample as a minimum of 2 times your frequency you will be measuring.

2.  The A/D converter has to be fast enough to measure your data rate.

3.  The resolution of your A/D converter will determine the amount of accuracy. If you have a 10 bit resoulution and +/- 1 mm it will limit your measurement ot +/- 2 micron limit.

4.  Note the resolution is +/- .05% full scale will determine your accracy of the measurement

[Broken_Arrow]

---

@Joseph Loo wrote:

You need to spec your requirements out.

1.  The device looks like a 20khz device. It implies that you will need to sample as a minimum of 2 times your frequency you will be measuring.

2.  The A/D converter has to be fast enough to measure your data rate.

3.  The resolution of your A/D converter will determine the amount of accuracy. If you have a 10 bit resolution and +/- 1 mm it will limit your measurement ot +/- 2 micron limit.

4.  Note the resolution is +/- .05% full scale will determine your accracy of the measurement

---

While I agree with all of your points, most of it is taken care of, especially at this stage in the OP's development:

#1 doesn't matter unless the OP is trying to measure distances dynamically, at a high rate of change, such as a fast moving robot arm. If we are measuring a stationary object - just for the purpose of getting the thing to work - the frequency response is a non-issue.

#2 & #3 are not a problem - the OP said he's using the PCIe 6321.

[Joseph_Loo]

______________________________________________________________________________________________

#1 doesn't matter unless the OP is trying to measure distances dynamically, at a high rate of change, such as a fast moving robot arm. If we are measuring a stationary object - just for the purpose of getting the thing to work - the frequency response is a non-issue.

_______________________________________________________________________________________________

You are correct about that. But the Laser has a limited tracking range, in order +/- 1 or 100 depending the device. I think his eventual goal iw either measurement of material going through a fix location or a frequency type measurement which would have high rate of change.

You are right about the A/D device, but then to measure the low voltages, he has to be careful about the grounding, etc.. otherwise he can get a lot of noise on the device and make the measurement useless.

[Joseph_Loo]

______________________________________________________________________________________________

#1 doesn't matter unless the OP is trying to measure distances dynamically, at a high rate of change, such as a fast moving robot arm. If we are measuring a stationary object - just for the purpose of getting the thing to work - the frequency response is a non-issue.

_______________________________________________________________________________________________

You are correct about that. But the Laser has a limited tracking range, in order +/- 1 or 100 depending the device. I think his eventual goal iw either measurement of material going through a fix location or a frequency type measurement which would have high rate of change.

You are right about the A/D device, but then to measure the low voltages, he has to be careful about the grounding, etc.. otherwise he can get a lot of noise on the device and make the measurement useless.

[Jolanta]

My fundamental aim is to scan te object by Laser and get the distance between the object and te Laser.

Analog Output metric, the Sensitivity Factor 

12.5 um/mV.

The 100-mm laser head range is over an output voltage of 8 VDC full scale,

So  to verify, we use:

12.5 um/mV   X 8 VDC or

12.5 um/mV  X 8000 mV DC

= 100,000 microns or 100-mm FS laser head range.

This is wat I feel.

So I have the analog voltage reading and the sensitivity factor(distance/voltage conversion factor),

This would give me the distance between the object and the Laser.