error in the registries, 4-20mA

[Mikel Tapia]

I´m using fieldpoints (FP-2020) to register the values (4-20mA) originating of a CFI (converter frequency - current). In some occasions fieldpoints have registered erroneos values, as if the CFI was not connected.

Is it possible that fieldpoint varie the impedance that the CFI is seeing and this alters the measures?

The CFI is VM9-F460 of "Bureau Wittich & Visser"

Thanks.

In spanish:

Estoy usando un fieldpoint (FP-2020) para registrar los valores (4-20mA) provenientes de un CFI (conversor frecuencia - corriente). En algunas ocasiones el fieldpoint ha registrado valores erroneos, como si el CFI no estuviera conectado.

Es posible que el fieldpoint varie la impedancia que el CFI está viendo y esto altere las medidas.

El
CFI es VM9-F460 de "Bureau Wittich & Visser"

[Ames]

Mikel,

Which I/O module(s) are you using to read the CFI? FieldPoint modules in general do not vary the input impedance that a sensor would see. What do you mean by erroneous values (slightly off, 0mA, or something else)?

Ames

[Mikel Tapia]

Helo Ames, thanks for your answer.

The I/O module we are using is FP-AI-C420 (4 to 20 mA analog input).

In certain periods (very random, for example once to the month during one hour), we have observed erroneous data. The registries gave values similar as if CFI (converter frequency - current) were not connected to fieldpoint FP2000 (0mA), which imply that appear values smaller of 4mA, something that does not have to happen, because the CFI always must give minimal 4mA.

After making different tests to the CFI, I have found two forms to reduce this 4mA: one is reducing alimentation voltage below 5V (but we have observed voltage has not lowered that 11V) and the second one is increasing the impedance of load. The load of the current output of t
he CFI must not greater then 500 Ohm to ensure a correct operation... In principle, the I/O module FP-AI-C420 impedance is 133 ohm.

[Ames]

Mikel,

One issue that a lot of people have with the TB-10 and the dual channel modules is that they don't get them seated in properly. This can cause a variety of issues one of which is intermittent behavior. Check to verify the following:

1. Make sure that both the top and bottom snaps are snapped in completely.

2. You should hear the two distinct snaps when putting the dual channel module into its slot.

3. Also make sure that the pins on the bottom side are not bent as one could have inadvertently bent the pins.

4. The red sticker on the TB-10 Dual channel module should always be on the top, away from the screw terminal.

I attached a Word document that has two images of how dual channel modules should and shouldn't look w
hen seated in the TB-10.

Next time you notice this intermittent behavior inspect the TB-10 and watch the Power and Ready lights to see if they are flickering or not. If the LEDs flicker than this implies that there are probably other issues. Is your TB-10 full of dual channel modules or does it have just the FP-AI-C420? What version of LabVIEW do you have? What version of NI FieldPoint?

Ames

[Mikel Tapia]

Hi Ames.

Well, problem appears in various equipments ( fieldpoint + CFI), with which I think that it would be dificil that in all the error was a bad connection. In any case I'll consider it.

About your questions:

Our TB-10 is full of dual chanel modules (four FP-AI-C420 and one FP-AI-V5B).

We are using Labview 6.1 and Fieldpoint explorer 4.01...

[James_S]

I am experiencing a similar problem with an FP-AO-C420 4-20 mA analog output module. If it's set on a value for a long period of time (could be hours or several days before it fails), sometimes it will drop to 4 mA and stay there. This is happening on 2 of 3 systems; the tird is fine. Modules are seated OK. I just swapped a module from one of the "bad" systems with the "good" one and I'm going to see if the error follows the module. I'v seen the failure with code running on an FP-2000 and an FP-2010.

[Salvador_Santolucito]

Hi James,

Please see if the problem follows the module. If it does, then we may need to RMA the module. When the module goes "bad," does it ever go back to working properly? If so, when does it go back to normal (on its own after time, only after powercycling, after resetting the module)?

-Sal

[James_S]

Sal-

Thanks for your reply. I just had another "failure, this one happened while I was sitting there. The failure confirmed that the problem did not travel with the 4-20mA module, but stayed with the TB-10 base. I did a little checking, and by wiggling the TB-10 on the DIN rail, I was able to get the power and ready lights to blink like a new module had been added. So, I shoved the "train" of Fieldpoint units together, and wiggled it some more. I couldn't get the lights to blink again, so I'm hoping this fixes the problem. I'll continue to monitor it and I'll post again in a week or so if I haven't seen any more failures. This might help the original problem in this thread too...

Thanks,

James S.

[James_S]

OK, I have more information on this error. I got the error again today on both the systems that have shown it before. The error did NOT travel with the module- the third system is stil OK. I am no longer able to replicate the error by wiggling the TB-10 base on the DIN rail, so that didn't fix the problem either. I did get an error flag set in the software that indicated a Fieldpoint command generated an error code (couldn't read/write to module, data out of range, etc.)

I'm going to try to build more tracking into the code to track down the specific error. I'm also going to see if my problem is related to Mikel's error that started this thread, and continuously read the data from a 4-20mA A/D module in the same TB-10, and log it to a file if it comes back 4.00 mA.

Does anyone have any other ideas? If the problems are related, then what? I guess I could add an FP-AO-200 analog output module, but it seems kind of silly to do that for one channel, especially if I don't know that it will solve the problem. That's why I went with the dual channel modules in the first place.

Thanks!

James

[Salvador_Santolucito]

Yes, lets see some more information about the error code you are getting. When you are saying that the error is not follwoing the module. Do you meen the TB-10 base? Or the actual dual channel module that fits into it? If the same TB-10 bases keep getting the same error but another TB-10 never gets it, I'd suspect that the errored TB-10 may need to be RMAed.

-Sal