mounting 3 pairs of omron sensor E3X-F21 at 25mm intervals to measure time taken by moving object breaking beams and connecting to 6601 counter/timer card

[loadaballs]

System is Windows ME Labview 6.1 6601 Counter/timer card. 3 pairs of Omron Photoelectric sensors E3X-F21 are mounted on a flat surface and as the object passes the first pair of sensors it starts timer1 and timer2.
As the object passes the second pair of sensors it stops timer1 and as the object passes the third pair of sensors it stops timer2
We have a known distance between the sensors so we are able to calculate the objects speed and position.
We need a wiring diagram to connect the sensors to the 6601 card.

[Brooks B.]

Since you know position and you want to solve for speed, you need time (delta position over delta time = speed)... To measure time with counters, you will do simple event counting (count events on source) using a known source (20 MHz internal clock would be the best choice). Now, you can control when these counters count by gating them. If the gate is active, they count up. If the gate is inactive then they don't count. So you need to set up your sensors to gate the counters. The PCI-6601 manual has a pinout for which pins correspond to the gate, source, etc for each counter. Ideally, you would enable the gate when sensor #1 detects the pass by and disable the gate when sensor #2 detects the pass by. How you acomplish this is up to you...

Good Luck!


Sincerely,
Brooks B
Applications Engineering
National Instruments

[Kevin_Price]

I think I can describe a method that'll probably be simpler than the previous answer because it won't require any external logic circuitry.

1. Configure two counters for "Two-Edge Separation" measurement, let's say counters 0 and 1.
2. Wire Sensor 1's signal to both AUX-0 and AUX-1.
3. Wire Sensor 2's signal to GATE-0.
4. Wire Sensor 3's signal to GATE-1.
5. Wire each sensors' 'ground' to the appropriate ground pins on your terminal block.
6. Software configure both counters to use "max internal timebase" for a source -- 20 MHz for the 6601.

You can specify the polarity of the transition you care about for both the AUX and the GATE signal, but I'll explain in terms of rising edges for both.
Counter 0 will count time from Sensor 1's rising e
dge until Sensor 2's rising edge. Counter 1 will count time from Sensor 1's rising edge until Sensor 3's rising edge. The count values will be in units of "# of 20 MHz cycles elapsed."

You can probably get a decent starting point on the software using one of the shipped examples.

[loadaballs]

please forgive my ignorance....but could you please clarify "shipped examples"
Can we wire these type of sensors directly to the 6601 card via a 68 pin connector block? or do we need a signal modification?

[Kevin_Price]

"Shipped examples" = examples that came with LabVIEW. Look for "Two Edge Separation Measurement (NI-TIO).vi" under the menu Help-->Find Examples. Read up on this type of measurement in your 6601 manual & here on ni.com. If the topic is still confusing, reply here and ask for some more help.

Regarding the Omron sensors: I don't know for sure whether you need signal conditioning. I tried looking up the datasheet, but all I found was that it has PNP-style output. I didn't find a spec on output voltage.
You'll want the signal to be TTL before you wire it to the connector block. I'd recommend a quick call to Omron, and ask them how to interface to a TTL data acquisition device. If conditioning is needed, they're in the best position to
specify what kind.

[loadaballs]

You have been most helpfull, we will try to proceed a little further with our project....THANK YOU.