1746-NI8 scaling problems

[Robb B]

Hi, having some issues with scalings (SCP commands) with some Vegapuls 65 guided wave radar level transmitters. I've set the min/max in the transmitters according to the measurements at the tank (horizontal cylinders, just for fun), and the dip tape and the transmitter local display agree, within an eighth of an inch over an approximate 10.28' span. Except for one transmitter, which won't let me change the Max adjustment from 1.89 and if I override it, get an F261 error (fault in configuration), let's leave that one alone for now. Hopefully the most important details are below:

Transmitter:
Min: 10.28 ft
Max: 0.0 ft
Update time: 0s

SCP as shown in attachments, as is the configuration for the card. I've got 4 temperature transmitters on the same card that work just fine, and a 3rd level transmitter that seems OK so far.

Is there something I'm missing? When I compared the configuration files from slot 7 to slot 2 (another NI8 card) they are different, but the only difference I can find is the filtering frequency is set to 1Hz compared to none. The values in the upper and lower custom ranges are grayed out, but are 0 vs -31967, but I don't think those are applicable since I'm using 4-20mA scaling on both, not custom or engineering.

Ignore the numbers in the SCP, that's from me trying to figure out what scaling actually works.

 

[James Mcquade]

How are the cards configured?
4-20ma or 0-10v
did you initialize each channel?
a 0-10 volt signal should give you an input of 0 to 32767
a 4-20ma signal should give you an input of 3277 to 16383
its been a while since i did an NI8 card.
james

 

[Robb B]

How are the cards configured?
4-20ma or 0-10v
did you initialize each channel?
a 0-10 volt signal should give you an input of 0 to 32767
a 4-20ma signal should give you an input of 3277 to 16383
its been a while since i did an NI8 card.
james

Cards are configured for 4-20mA, each channel appears to be initialized in rung 2 on first scan, as per the wizard. From the manual, I think 4-20 is -32767 to + 32767. The other NI8 card and 4 of the inputs on the same card are configured this way and work great.

 

[Robb B]

Notes to future me:

Well I think I've got the problem narrowed down to the sensor itself. If I make the Tank 1 sensor output a 0 or 50% value, the HMI (by way of the PLC's SCP) displays the correct value. Tank 2 still reports a configuration error (F261) whenever I try to make changes to the min/max ranges. Currently waiting for response from Vega about that. Going to try to setup a spare sensor in the meantime.

 

[drbitboy]

since this is a radar sensor, I assume the measurement is a distance from the sensor location down to the surface, so a greater distance measured is a lesser level, and vice versa. Can whatever scaling is in place handle a negative slope between its inputs and outputs?

 

[Robb B]

since this is a radar sensor, I assume the measurement is a distance from the sensor location down to the surface, so a greater distance measured is a lesser level, and vice versa. Can whatever scaling is in place handle a negative slope between its inputs and outputs?

Yes, it's just a matter of swapping the min and max values. Most transmitters (and PLC inputs!) are quite ok with a higher value in either the min or max.

I got the problem solved: new (used) sensor installed with proper min max values gives very accurate readings!

thanks for everyone's suggestions!