Analog inputs - Ohms

[Milosh]

Hi all,

What mean when you set Ohms for analog input?

Is that regarding potentiometer or?

Is there any manual which describe all options?

 

Best regards,

Miloš

[Ausman]

What PLC? What I/O?

[Milosh]

Hello,

Vision V290, with snap in module V200-18-E4XB...

Thanks

[Isakovic]

Maybe you mean input impedance for 4-20 mA?

You see how many ohms your transmitter can supply, and this should be less or equal to sum of all analog inputs impedances through which current signal is running. You should worry about this only if you have more than one analog input on a single 4-20 transmitter.

[Ausman]

Hi Milosh,

It is unusual for the specific measurement of Ohms on most Unitronics gear, hence Isak's suggestion/answer.  But this module is one of them and my understanding is that the Ohms setting lets you read a range of 1-320 Ω at 0.1 Ω resolution.

I have attached the pdf manual which mentions this.

cheers,

Aus

V200-18-E4XB.pdf

[John_R]

This is a PT100 input, which is based on a resistance measurement principle where 0-degrees C = 100 ohm, and changes about .4 ohms per degree.

so it would seem that 1-320 ohm is basically the range of a PT100 sensor.

So if you ever have the need to precisely read a resistance in a project, there you have it.......

 

JohnR

[Milosh]

Thank's a lot ,

I understand.

Miloš

[Ausman]

So has anyone played with "Raw Value" underneath the Ohms indicator?  I can't at present, and in answering this question I also can't find info about how Raw works.  Seems a bit airy fairy,....what...you can just chuck anything at it and get the read direct?....but what?......mv, ma...huh?

cheers, Aus

 

[sgull]

Hi

I think if you choose PT100 it automatically converts the input to actual temperature values and you don't need to linearise.

If you use the OHM setting you can use the raw value in the ladder and scale it to whatever you like.

I assume the range of 0 to 320 ohm is the same for both. Would be worth setting up to test though.