1769-IF8 not reading values

[bradal]

Hey guys,

Been a while, I have an odd one. Something that should be straightforward.

I have a 1769-IF8 module, looking to add an analog, been in operation for couple years.

I have 6 single ended inputs working on input 0-5 with no problems. With those I obviously have the jumper in place to ANLG COM.

I am adding a 4-wire device to 7th input. This requires connection to Iin 6+ and V/I in 6-. Seems pretty straightforward.

Doesn't work. I moved it to the 8th input, same thing 0mA. I am 100% sure that the ANLG common jumper is not in place.

I moved on of the single-ended inputs onto one of those (with jumper) works fine.

I measure the current inline, 4 mA as expected. When I unpair my remote device, drops to 1.8mA as expected.

Tried 0-20, 4-20 etc.

Also worth noting, when producing 4mA, I see about 1V across terminals and 0.47 at the 1.8mA which correlates to the 250ohm load of the card.

Nothing ever reads into Local CH Data register.

Thoughts?? I'm stumped.

 

[Jim3846]

Publication 1769-UM002B-EN-P - July 2005
3-22
There is a configuration word for each channel.
Do you have the these bits enabled for that channel?

from manual below from 3-22:
Channel Configuration
Each channel’s configuration words consist of bit fields, the settings of which
determine how the channel operates. See the table below and the descriptions
that follow for valid configuration settings and their meanings. The default bit
status of the configuration file is all zeros

 

[bradal]

Yes, confirmed on bit fields and configuration dialogue and by also moving another analog to that channel.

 

[Engineerj22]

Maybe you got the + and - backwards? happened to me once.

 

[bradal]

Yes, confirmed that it wouldn't damage anything and reversed polarity. Same result.

 

[johnd_125]

My first thought was you didn't have the channel enabled in the Controller Organizer=>Module properties=>configuration. But I believe you said one of your single ended inputs works on Ch6, so all must be good there.

In module configuration, are the alarms enabled and set to something goofy? Input range and data format are set properly?

Your 4 wire device is powered by 24VDC, the same power supply as the loop powered inputs? I guess the neg. on it must be connected to one of the ANLG com on the module if your loop powered inputs are working. Of course all the ANLG com on the module are internally connected.

Do you have a mA signal generator you could use to give the channel a differential mA signal?

 

[bradal]

Thanks for the reply.

Unfortunately I do not, working remotely on a site and they do not have one. Looking at sourcing a Fluke 789.

I think in the interim, I may move the module to one of my remote I/O racks and connect to a Point I/O Module to confirm it is working.

Any other suggestions? Like I say, I have done this a number of times, and for the life of me cannot see what I am missing.

 

[bradal]

Update. I moved the unit to a remote rack, 1734-IE4C.

When connected I get over range value 21388.

The manual states that they are single ended inputs but then shows wiring of a 4-wire device. This should work fine as wired. Input 3 and common.

 

[Bit_Bucket_07]

The manual states that they are single ended inputs but then shows wiring of a 4-wire device.

Why do you view that as a problem? A 4-wire transmitter can be connected to a single ended analog input.

 

[johnd_125]

Unfortunately I do not, working remotely on a site and they do not have one. Looking at sourcing a Fluke 789.

Fluke 789 is nice and may be necessary for accurate calibrations.

But for just sending/receiving a quick and dirty 4-20 mA signal, I have a cheap piece of Chinese kit called "Mr. Signal" that works well just for testing purposes. Its small and fits in my bag and has worked for years. I consider it as essential as a multi meter for testing panels and doing startups that have analog in them. I paid less than $50 for it.

 

[bradal]

Why do you view that as a problem? A 4-wire transmitter can be connected to a single ended analog input.

I may be wrong but an actual 4-wire device cannot be wired single ended. Single ended assumes that the analog common is connected together such as a 2-wire or 3-wire device. A 4-wire is differential and isolated from the + and - of the power supply of the device and should have two wires connecting to the analog module.

This specific devices seems to have an issue when I connect the - of the analog to the - of the 24V supply or in the case of the IE4C module to the common that is connected to the -24V power supplying the rack.

In theory, yes, you should be able to wire a 4-wire device as single ended with the negative of the analog being tied to negative of the supply but this device does not seem to have the same reference point on each wire, causing over current.

 

[Bit_Bucket_07]

I may be wrong but an actual 4-wire device cannot be wired single ended. Single ended assumes that the analog common is connected together such as a 2-wire or 3-wire device. A 4-wire is differential and isolated from the + and - of the power supply of the device and should have two wires connecting to the analog module.

This specific devices seems to have an issue when I connect the - of the analog to the - of the 24V supply or in the case of the IE4C module to the common that is connected to the -24V power supplying the rack.

In theory, yes, you should be able to wire a 4-wire device as single ended with the negative of the analog being tied to negative of the supply but this device does not seem to have the same reference point on each wire, causing over current.

Sounds like you may be working with a transmitter that doesn't have an isolated output. You may need to use a signal isolator to connect your transmitter.

 

[bradal]

Agreed. Have one on order and will update thread if it fixes issue.

Why doesn't the IF8 input act as an isolated input when not jumpering the ANLG COM terminal?? Doesn't make sense, thought that was the point of the ability to mix input types......

 

[Mickey]

Agreed. Have one on order and will update thread if it fixes issue.

Why doesn't the IF8 input act as an isolated input when not jumpering the ANLG COM terminal?? Doesn't make sense, thought that was the point of the ability to mix input types......

See pdf's

As others have said it would work if all are using the same power supply.