Suggestions for converting amperage to voltage loop

[Dryhops]

I recently replaced a set of gas sensors wired to a micrologix 1400 L32AWAA. These new ones are 4-20mA and I didn't notice until install that the analog inputs of the 1400 are 0-10v. Took an hour of troubleshooting my scaling before I realized the obvious.

Conceptually, I understand that I can add a resistor of the appropriate ohms to 'convert' the sensor output from an amp loop to a voltage, but I've never wired up something like this.

Can anyone recommend their preferred solution for adding resistors in a cabinet? What components are typically used for a professional looking install? Searching around, I see many signal conditioners do what I need, but they would be more expensive than just buying more IO. Something inexpensive would help and make my oversight less costly.

Thanks for your time!

 

[lfe]

Just put a 500 ohm resistor on the input terminals and you'll have 2V for 4mA and 10V for 20mA.

It is recommended that the resistance be of high accuracy, 1% or better

 

[rupej]

When I've had to do this, I just put the resistor on the non-field side of two terminal blocks. You can heat-shrink the leads if you're worried about shorts or anything. Never had any issues but obviously just getting an IF4 or an IF2OF2 would be the preferred choice

 

[Dryhops]

Is there a specific type that should be used? Something that is low noise I assume

 

[rupej]

The resistor? There's no noise rating on those. Just get a 500 ohm with ~1% tolerance rating, or whatever accuracy you need. Alternatively, if you have a box of low-tolerance 500 ohm resistors, you can just measure them until you find the one closest to 500. Resistor needs to be rated for at least 1/4 watt.