How to connect an electromagnetic flowmeter to a module 9203?

[Rodzynek]

Hello,

I have an electromagnetic flowmeter which gives me 4-20mA measured signal. I am trying to read this signal using 9203 module. As it was written in the datasheet I have to use external power supply. I have 2 wire from my flowmeter Aout+ and GND. I connect Auot+ to Power supply + and then GND to AI0 after that - from power supply to Com in 9203. Do I do everything correctly? I cannot see any values changing.

Thank for any help.

[AdnanZ]

The 9203 doesn't expect an external power supply. Where did you see that? You can connect single-ended current signals to the NI 9203. Connect the positive lead of the current signal to the AI terminal, that's your Aout+. Connect the negative lead to the COM terminal, that's your GND. And, that should work. For the future, be sure to have a look at the following:

NI 9203 Operating Instructions and Specifications

[Rodzynek]

Adnan Z,

Thank for replay. At the beginning I did it how you said but I have only that kind of range of my signal (please look at an attachment as flowmeter). It should be something around 8mA but I see very low values. The changing data are correct but it looks that it is scaled somehow. The module is new and I do not change scaled values it is set by company.

About additional power supply I read here:

http://zone.ni.com/devzone/cda/tut/p/id/6940

But maybe I did not take it correctly.

I have this kind of sensor:

http://www.flowmeter.be/downloads/Instr_Minimag146E.pdf 

With my old system it works correctly. Therefore I was surprised that I got what I got. And I do not know where is problem.

[Stephen_Moore]

Hi Rodzynek,

I fear that you may have a problem.  The 9203 is a 4-20ma current sinking device, i.e. it passes the signal through a 100 ohm resistor down to ground.  Your flowmeter seems to be a sinking output, i.e. the current is controlled referenced to ground.  In general you can not connect a sinking output to a sinking input as current can not flow in two directions.  If your device is a sinking output then you will need to either use an isolator so that you can use the 9203, or use a NI device that will act as a current sourcing (i.e.. does not have one end tied to ground) or floating input.

I have found that the 9203 can be prone to giving a noisy signal and usually have some form of filtering in the signal.  The output that you show in the jpg could just be noise.

If your device can act as a current source then you connect the Aout+ to the AI0 and the GND to common, if your device acts as a two wire current device you may need to connect an external PSU then the wiring would be PSU+ to Aout+ to GND to AI0 to Common to PSU-.

I find the the use of a DVM (measuring current) or a loop powered ma display in series a valuable tool in troubleshooting 4-20 ma loops.

The manual also states that the output from your flowmeter can be 0-10Vdc 0-20ma as well as 4-20 ma, it can even be reverse acting so it might pay to check that the settings are correct if you have not already.  Sadly the manual does not state whether the ma output is sourcing, sinking, or  isolated.  Start with a DVM or equivalent so that you can see what the signal is and work from there.

Hope this helps.

Cheers

Stephen

p.s. Hi Adnan

[Rodzynek]

Hello Stephen,

Thank you for replay. It makes sense what did you say. I have an addition Opto22 system with this module:

http://www.opto22.com/site/pr_details.aspx?cid=1&item=SNAP-AIMA-4

It seems to be isolated module and with this module I see everything perfect. I sent email to the provider of my flowmeter with a question which kind of output is there. I tried with external power supply loop as you said but then the signal is constant nothing change but it should..Therefore I post a message here. 

[Stephen_Moore · Accepted solution]

Hi Rodzynek,

Have you tried looking at the output with only a DVM or similar on the output?

That would be a good guide to tell you what the signal actually is. 

The 9203 gives a FXP signal in Amps so if you were expecting 8ma than your jpg is showing 7.16 to 7.74 ma which is close.

As I said earlier I have found that the signal from the 9203 is rather noisy and apply filtering to clean up the signal, I would imagine thatas you are measuring flow the signal would not change very quickly compared to the 9203 sample rate.

Also check to see if the output GND is connected to the other GND signals.

Cheers

Stephen

[Rodzynek]

Stephen,

You have just shot me with this sentence:/ -> you were expecting 8ma than your jpg is showing 7.16 to 7.74 ma which is close.

With my old system I saw data in mA between 4-20. The NI shows in A. Therefore it is 1000 less I mean it shows in scaled values to amperes. I thought that it is wrong values but I was wrong...

Thank you for fast response and I am sorry for stupid questions. I have to lose my old habits.

[scott_white85]

i also have the same problem with my electromagnetic flowmeter. does anyone knows how to troubleshoot this kind of electrical equipment?

[Nemesis]

scott_white85,

Which kind of problem do you have? Could you explain it more deeper? Maybe I would be able to help.

Kamil