shoelesscraig
Member
Hey guys,
I have a level sensor, Flowline LU20, for a tank we have here. It is a simple 4-20mA output. However, the company that installed the system installed a Micro 810 PLC which only has 0-10V inputs.
I know you can use a resistor to help convert, but I need a little more help than that. On the original wiring directions from the manual (below on page 4) it shows that you need a 250 Ohm resistor across the 2 wires at the PLC. This of course is if you have a PLC designed for 4-20mA input.
http://www.flowline.com/pdf/ultrasonic-level-measurement/echotouch-lu20-m.pdf
Since I only have 0-10V input, what could I do to make this 4-20mA become 0-10V? Resolution is NOT a worry here. Really, a ballpark close number is OK. It is a VERY non critical level.
I read somewhere about putting a 500 resistor across the input, but I'm not sure if that applies being as the directions already recommend a 250 ohm with the proper setup.
Also, the OEM installed a resistor, I believe it was 170 ohm, in series with one of the leads. Not sure why they did this. It doesn't seem to make the voltage fluctuate hardly at all as the level rises in the tank.
FYI, the sensor is brand new and calibrated, and gives me 4-20mA when connected to another setup, so I know it works.
Any help would be awesome. I would love to know the math behind this trick too if any of you math buffs would like to share...
I have a level sensor, Flowline LU20, for a tank we have here. It is a simple 4-20mA output. However, the company that installed the system installed a Micro 810 PLC which only has 0-10V inputs.
I know you can use a resistor to help convert, but I need a little more help than that. On the original wiring directions from the manual (below on page 4) it shows that you need a 250 Ohm resistor across the 2 wires at the PLC. This of course is if you have a PLC designed for 4-20mA input.
http://www.flowline.com/pdf/ultrasonic-level-measurement/echotouch-lu20-m.pdf
Since I only have 0-10V input, what could I do to make this 4-20mA become 0-10V? Resolution is NOT a worry here. Really, a ballpark close number is OK. It is a VERY non critical level.
I read somewhere about putting a 500 resistor across the input, but I'm not sure if that applies being as the directions already recommend a 250 ohm with the proper setup.
Also, the OEM installed a resistor, I believe it was 170 ohm, in series with one of the leads. Not sure why they did this. It doesn't seem to make the voltage fluctuate hardly at all as the level rises in the tank.
FYI, the sensor is brand new and calibrated, and gives me 4-20mA when connected to another setup, so I know it works.
Any help would be awesome. I would love to know the math behind this trick too if any of you math buffs would like to share...