AB 1756-IF4 Analog Module Overrange Bit Not Setting

[raccjim]

I have a bit of a problem that I can't seem to find the answer to in my literature. I have an AB 1756-IFX0F2F Series A Analog Combination module with firmware Rev. 1.004. My problem is this: When a channel is configured for 0-5v., my overrange bit sets at 5.26 volts as it should. Yet if I configure a channel for 0-10 volts, the overrange will not set as designed when 10.5 v. or greater is applied. Any guidance would sure be appreciated!

 

[raccjim]

Hi folks, sorry to bring this post back to the front of the line again, but I'm still hoping someone may be able to help me with my analog card situation. I am just having a hard time figuring out why underrange works on one scale but not another. I have re-flashed the firmware and done a calibration of each channel...Hopefully someone out there can provide some insight,thanks.

 

[labeledas]

are you sure it's seeing over 10.5V and did you change anything else like disabling alarms?

Be careful when ‘disabling all alarms’ on the channel because it also
disables the underrange/overrange detection feature. If alarms are
disabled, overrange/underrange is zero and the only way you can discover a
wire-off detection is from the input value itself. If you need to detect a
wire-off status, do not ‘disable all alarms’.
We recommend that you disable only unused channels so extraneous alarm
bits are not set.

Also what values are you seeing in the data tag for that channel?

 

[raccjim]

Hey, thanks for the response. I have not disabled the alarms and I can supply 11 v.to the channel input. (verified). Channel is scaled 0-10 physical to 0-100 engineering units. This is where it gets odd, at 11 v., my tag values shows as 104.73. My simple math head tells me that it should be 110.00. I would assume then, that I would need a tag value of 105.1 or so to set the overrange as AB says overrange for that scale is 10.5 v. I'm at a loss for what is clipping the value...

 

[spaderkung]

Is 11V measured when voltage source is connected to the card? Just to be extra clear...
Is it 1 physical card that you try? It could be faulty. But on all channels.. strange.

 

[raccjim]

Yes, I've measured input voltage at the card and it is indeed receiving signals up to 11 v. Labeledas mentioned that it would be the tag data that sets the bit; at a lower scale (0-5)the data is not inhibited and the overrange sets, but at 0-10 the tag will not show higher than about 10.4 even though the applied voltage is higher. It acts like there is a high limit latch but I don't see anything in parameters that would cause it...I'm at a loss right now. I can use high limit alarm to do what I need but it's the not knowing why that is bugging me!

 

[Contr_Conn]

It's been more than 2 years since I touched this module, but as far as I remember, ADC converter on this module cant go above 10.5V, and in reality is it may be even less than that.
As a result module clamps that reported value. And it's possible that clamp is at 10.473 V like you see it.

One thing I see for sure is that you module is very old.
Current rev is 3.5
I would recommend to open TS ticket and ask them to duplicate.

Edit:
I have found old manual (2002) for your Ser A module: it states that Ovverrange should come at 10.5 and 5.25 V respectively.
So if module clamps value at 10.473 then overrange will never happen.
Try Ser B module

 

[raccjim]

Yeah, that's what it looks like... I have the manual as well, and it does work properly at 5.25, just won't get to 10.5. I do have the Firmware update, I've been a little reluctant to try it as I have to wonder what change may bring. Guess I'm getting too cautious in my old age. Thanks for the advice!

 

[Contr_Conn]

I don't think FW update will fix the clamp. But it may correct the Overrange settings.I have a module but no time try it now.

Also I see that other modules have Overrange at 10.25V that makes sense.

 

[raccjim]

I'm not giving up yet, I'll play with it some more after the weekend...
Thanks for the replies!