programatically check if sensors are connected

[Steffen01]

Hello,

is there a programmatic way to check, if there are sensors connected? Say to a NI 9217?

Maybe just have to check, if it reads some values way out of range? With nothing connected I got 1200 or so degrees, so if I just check if its more than 60, then means the input went to full resistance and nothing is connected?

Its on an etherCAT slave, but that should not make much difference.

Cheers,

Steffen

[GerdW · Accepted solution]

Hi Steffen,

we are using a simple scheme on our testbenches…

- the user can select 3 ranges for each sensor value: working range, warn range, alarm range

- as long as the value is inside the working range, everything is ok

- when the value is outside the working range, but in the warn range the user gets a warning (with no additional action)

- when the value is outside the warn range, but inside the alarm range then user gets an alarm/warning and an additional emergency action is triggered

All you need from this is a simple check for the (expected) working range of your sensor values…

[Steffen01]

Hi Gerd,

the idea is more, there can be between 1 and 48 sensors connected. If I check in advance, which one is connected, I only have to transfer and log data for these. I could make something with radio buttons, where the user selects, which sensor is connected. But that sounds trouble. Easy to program though, already done. Plus made something that automatically makes the SQL string.

Guess I work out the maximum values on each module, which indicates open inputs.

[PiDi]

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@Steffen01 wrote:

Maybe just have to check, if it reads some values way out of range? With nothing connected I got 1200 or so degrees, so if I just check if its more than 60, then means the input went to full resistance and nothing is connected?

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That's the way to do it 🙂

Side note: thermocouple modules 9213/9214 have Open Thermocouple Detection option, which... well, detects open thermocouple 🙂 I'm not aware of any other modules that have such functionality (maybe some bridge modules?). Mainly because any analog input actually measures the potential between two points, so there is really no way to universally define "open connection". What you measure with your module is just "very high" resistance, so it's up to you to decide if that's proper reading or error.

[Steffen01]

yes, one of them is 9214. So I will check that, thanks

[Steffen01]

I will send all the values from the cRIO and filter them on the PC host side. Then I don't have to recompile things all the time, can preview the data and maybe at the end set up some .ini file to store filter settings. Then I don't have to change the PC side of the software all the time either.