configuring the 1327 in MAX

[LV_Pro]

Hi All,
I'm having some difficulty findin the right combination of settings, hardware and software, to configure an SCXI-1327 to work with a SCXI-1126 for making frequency measurements of a speed sensor signal. The sensor's signal is a low going pulse, from 12V to 0, 4 pulses per revolution, so it is normally high when there at 0 RPM. The max RPM is about 6000, which gives us a max frequency of about 400Hz. I have not been able to find a combination of settings of threshold, hysteresis, low pass filter, etc. I'm also having difficulty with the 1327 in Max, where there are configuration settings for the attenuator. I have tried to set the attenuator to 1:1 in box the 1327 and its configuration in MAX, but everytime I go back in the configuration for the channel it is at the diffault setting of 100:1. We've tried to resolve this for a few days, without success, and need it running, so any suggestions are welcome.
LabVIEW 7.1.1, MAX 7.2.

Thanks,
Putnam Monroe

[LA 75]

Hello,

The following tutorial
should help you out getting started with the SCXI-1126. Please let me know if you have any questions about it.

Regards,

LA

[LV_Pro]

Thanks for the response. My problem is that I am trying to set the triggering for the 1126/1327 combo and am having no luck getting it to read the signal. I wrote the code using DAQmx, partly to become more familiar with it, partly because my customer has taken the LV basic courses and that is what they would show them. I had seen the examples, but it isn't clarifying the issues that I have. The first is that when I configure the 1327 under NI-DAQ and set the attenuator to 1:1 (vs the default of 100:1) it doesn't have me save anything (like it does when creating or changing a DAQmx task for instance) and when I go back in to look at the attenuator setting it shows it at 100:1, leading me to wonder if I actually had changed it. The setting in NI-DAQ is supposed to match the actual physical attenuator setting in the 1327. I also have not been able to find any setting of the trigger or hysteresis that works, either in NI-DAQ test panels or my LabVIEW code. What I need is some guidance as to what values (filter cutoff, max frequency, level, hysteresis, etc.) are appropriate for a signal that consists of 12V going to 0V, square pulses, ranging from near 0Hz to 400Hz?


Thanks,

Putnam Monroe
Certified LabVIEW Developer
North Shore Technology, Inc. a National Instruments Alliance Member

[LA 75]

Hello,

The attenuation settings on the 1327 have a switch which allows for either 1:1 or 100:1 attenuation. The default hardware setting is 1:1 and the default software setting is 100:1. The hardware and software settings must match in order to get a correct reading in Measurement & Automation Explorer (MAX). The gain will have to be equal to 100 in order to get a valid reading out of MAX if the attenuation is not reconfigured in software.

For example, if the hardware gain on the SCXI-1121 is set to 1:1 then the software gain will need to be set to 100. If the hardware gain is set to 10 then the software will need an additional 10 in order to get a valid signal.

When the attenuation values match the hardware and software gain settings will need to match for both the 1121 and the 1327 to get correct readings. In order to access the software attenuation settings you may follow these instructions:

To do this:

1. Open MAX
2. Expand Devices and Interfaces » NI-DAQmx Devices » SCXI
3. Right click on X : SCXI-1121 and select Properties…
4. Select the Accessory Tab
5. Click on Configure…
6. Set Attenuation to 1 or 100
7. Click OK to save configuration

Hope this helps,

LA

[LV_Pro]

Thanks,
It is an 1126 that I'm using and the hardware is set to 100:1 at this point. One of the problems that I was having is that when I go into Max to configure the attenuator setting it tells me it is at 100:1. If I set it to 1:1 to match the hardware (which I had changed to 1:1) and I exit the attenuator configuration and then reenter it is says 100:1 again, not the 1:1 that I had just set it to. So, when I set it to 1:1 and exit, is it really 1:1? I have been trying all kinds of different settings for the hw attenuator, the software, the threshold, the hysteresis. What are reasonable settings for the filter (1Hz?), the min-max frequencies (0 - 1000Hz?) the attenuator (1:1, 100:1?) the threshold and the hysteresis, to measure an 20 - 600Hz signal, with a square waveform, with an amplitude of 12V (0 - 12V p-p)? Pretty much this is the final thing to fix to get a new test stand running, but we haven't been able to find the magic numbers, or, is the 1126/1327 bad?

Thanks again,

[Logan_K]

Hi Putnam,

I have seen this problem before - I believe this is a bug in MAX that is being investigated. The way I got around it last time was to delete the SCXI chassis from MAX and then start over. If that doesn't work, then try resetting your DAQmx configuration in MAX by going to Tools>>NI-DAQmx configuration>>Reset NI-DAQmx Configuration.

I hope that helps.

-Logan

[LV_Pro]

Thanks! Do you know whether it might have been addressed in Max 7.4? I have it installed on a couple of machines, haven't put it on this customer's, like to have as few variables as possible and 7.4 is really big, took up most of my 1Gb memory stick that I use to transport code from my development machines to the customer's.

Any suggestions regarding the other settings (threshold, etc.) for the signal I've described? I've tried many variations without success, the signal looks pretty clean, at the SCXI end, on a scope. Of course if there is a configuration issue in MAX ...


Putnam