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Old February 6th, 2018, 10:28 AM   #1
Dood
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Flowmeter 4-20mA Input Signal

Hi,

I have a 4-20mA Electromagnetic Flow meter which is externally powered. I have a 24VDC supply powering the meter (which is powering up correctly - screen lights up and shows values etc.)

I am using a Siemens SM-1234 4AI card. Separate from the power, I have my "0+" on the AI module hooked up to "I+" on the flowmeter and the "0-" on the AI Module hooked up to "COM" on the flowmeter. When I power up the rack - the red fault light comes on the card and the processor.

Any idea what I am doing incorrectly? Thanks!
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Old February 6th, 2018, 12:45 PM   #2
Dood
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To clarify - the Diagnostics show "High Limit Exceeded" which would make me think short circuit, but I don't see how that's possible.

Thanks!
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Old February 6th, 2018, 01:07 PM   #3
cardosocea
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Who is supposed to be powering the loop? The IO card or the Flowmeter?

If they are both trying to power the loop, what you mentioned can happen.
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Old February 6th, 2018, 02:11 PM   #4
Dood
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Quote:
Originally Posted by cardosocea View Post
Who is supposed to be powering the loop? The IO card or the Flowmeter?

If they are both trying to power the loop, what you mentioned can happen.

The flowmeter should be powering the loop. The IO card cannot.

I've attached the wiring diagram that I've found for the flowmeter - it was ordered from China so the language is a little confusing and the terminals aren't consistent. I'm currently trying to use the 4-wire configuration with no luck.

Thanks again!
Attached Images
File Type: jpg Wiring.jpg (20.9 KB, 46 views)
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Old February 6th, 2018, 03:16 PM   #5
cardosocea
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Also, is the card configured for current measurement?

Do you have a loop calibrator to figure out one of these at a time?
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Old February 6th, 2018, 03:33 PM   #6
Dood
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Quote:
Originally Posted by cardosocea View Post
Also, is the card configured for current measurement?

Do you have a loop calibrator to figure out one of these at a time?
The card is configured for 0-20mA input.

I have a fluke 787 and when I use the Source mA function I put my "+" to the "0+" terminal and the "-" to the "0-" terminal, the module flashes the same error light. Like it won't even accept a simulated 4-20mA from my Fluke. Am I doing something wrong with the fluke?
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Old February 6th, 2018, 03:58 PM   #7
tarik1978
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Is the card correctly configured did try another channel?
As a test, reconfigure the hardware to 0-10 or +/- 10V rather than 4-20mA.

Now across the input terminals for that channel, add in a 500 Ohm resistor.

Now measure the channel signal in voltage right across those terminals.

If it reads properly and stays in range while you operate the field device, your field device is working properly.

If you find the voltage runs high and out of range, your field device may not be configured properly, or the wiring may have been done incorrectly.
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Old February 6th, 2018, 04:02 PM   #8
tarik1978
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If the flowmeter is 4_20mA then the card should be configured the same
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Old February 6th, 2018, 04:12 PM   #9
Dirt
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Quote:
Originally Posted by Dood View Post
The card is configured for 0-20mA input.

I have a fluke 787 and when I use the Source mA function I put my "+" to the "0+" terminal and the "-" to the "0-" terminal, the module flashes the same error light. Like it won't even accept a simulated 4-20mA from my Fluke. Am I doing something wrong with the fluke?
Did you try to bridge M to 0-?
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