convert 4-20ma to 0-10v with resistors?

[TimD]

Hi, I have a MicroLogix 1100 PLC, and it has two 0-10v analog input channels. Is there a way to convert a 4-20 ma loop powered device for use with this PLC? I thought I could use 250 ohm or perhaps 500, but am unsure.

Thanks!

 

[keithkyll]

500 ohm. Range will be 2-10 volts.

 

[TimD]

OK, fair enough! One more question, resistor ACROSS the two input terminals or in series with one of the input leads?

Many Thanks!

 

[keithkyll]

Across

 

[TimD]

Thanks keithkyll

Great (and very fast!) advice!

Cheers.

Tim

 

[andrewf]

Also note that it should be a precision resistor.
The recommended is a 500ohm low-drift precision resistor valued at 0.05% or 10ppm and 1/4 watt.

Personnaly i don't use that high a precision resistor but dont go using a common 5% or 10% one either.

Cheers,
Andrew

 

[keithkyll]

Agreed. 1% and 2% can be found on the shelf.
There is 2 factors to consider. Some may think you can just measure actual resistance with a precision meter, but that's not enough.
The tolerance is also over time as the resistor ages. You can help reduce this a little by oversizing. Use a 1 watt resistor, for example. At 20 mA, it will never get much above room temp, so no thermal induced aging. Put shrink tube over it so humidity, etc. doesn't attack it.
Do these things and you can relax a little if 2% is the best you can find.