Measuring Ohms with Compactlogix

QvixoteRoux

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Q
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Jun 2014
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Reynosa
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Hello Guys


One customer has a product that includes a coil that operates with 12 VDC, they currently are measuring current consumed by the coil and then calculate the resistance in Ohms, but now they want a separate/ dedicated Ohm-meter that can measure Ohms directly and interfaces via Ethernet/IP with the PLC.

Does anyone here has used something that can recomend? We already bought one module that was supposed to be Ethernet/IP but ended being TCP and was a pain to interface, also very slow measuring.




Any help is appreciated


Thanks
 
Maybe an RTD module can do the job. It measures resistance or temperature based on configuration I guess.
Never tried to do it, buy you may explore
 
Thank you for all your answers and suggestions.


The most aproximate to what I am looking for is the Laurel that rootboy mentioned. I skipped a couple of important specs that are that the device should have a display to visually read the measurement and that it can be capable of measure Ohms by itself without the need of interpreting an analog signal, this is why we cannot use transducers (and I also use a lot cr magnetics).

The Laurels is the one we bought, already installed it but the customer is not happy with it because does not have real ethernet/ip communication and is slow to take measurements.
 
This might actually be better for your purpose:

https://www.laurels.com/laureates.php

It can read resistance directly, and has an Ethernet option. But that may leave you with the same communication issues.

When you say slow measurements, what period are you looking for?

Edit: And what resistance range?
 
Last edited:
I would think you can just measure current with an alarm when it changes? Change in resistance will cause change in current if voltage is constant.
 
I have been checking with all the answers and links provided, thanks





a062549 said:
OK, I'll ask: Why are they doing this, measuring and remeasuring the impedance of the same coil?

o_O :confused:
Click to expand...


I dont understand your question, customer wants a device that is specialized in measuring resistance/impedance, not specialized in current and leaving the math to the PLC, they had already problems selling defective products using the method of measuring current and calculating the Ohms in the PLC
 
rootboy said:
This might actually be better for your purpose:

https://www.laurels.com/laureates.php

It can read resistance directly, and has an Ethernet option. But that may leave you with the same communication issues.

When you say slow measurements, what period are you looking for?

Edit: And what resistance range?
Click to expand...




Resistnce optimal range is between 13 and 17 Ohms already incluiding over the limits


Time for measurement under 250 mS




They currently are measuring the current when applying voltage to the coil for other testings and with this measurement calculating the resistance in the PLC, I honestly think is pretty accurate but they got this crazy idea and are putting a lot of pressure
 
It appears that they need a resistance test for coils. The Laurels module will make that measurement by sourcing a current (through the coil, reading the voltage drop and reporting the result as a resistance value.



That will work as long as the coil is not energized by a control circuit.



Resistance measurments need to be made on passive components, in this case the coil, not in an active, powered circuit.
 

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