4-20ma to Temp. using SCP

tjoneill

Member
Join Date
Jul 2007
Location
Michigan
Posts
66
Hello everyone,
I have a little problem converting a 4-20ma signal to display a temp, reading on a PanelView.
I have a RTD wired into a temprature transmitter that is wired into a AB 1746 N1041 analog input/output card.
The instruction i am using is a SCP instruction (RSLogix 500)
All we want to know is if the tank we are trying to read is freezing or not.
So, does anyone have an idea on how to set up the SCP instruction w/ out producing a 4ma and a 20ma to produce raw data for the input min.and input max,for I dont have the means to produce the signal.
Thanks again all
 
Hello everyone,
I have a little problem converting a 4-20ma signal to display a temp, reading on a PanelView.
I have a RTD wired into a temprature transmitter that is wired into a AB 1746 N1041 analog input/output card.
The instruction i am using is a SCP instruction (RSLogix 500)
All we want to know is if the tank we are trying to read is freezing or not.
So, does anyone have an idea on how to set up the SCP instruction w/ out producing a 4ma and a 20ma to produce raw data for the input min.and input max,for I dont have the means to produce the signal.
Thanks again all

You would need to know the Range setup on your Temperature Transmitter. i.e. 20°F to 80°F. Then use those in your SCP Instruction along with the Min/Max Numbers from you Analog Input Card. The Min/Max Numbers will be in your Analog Input Card Manual, and the Temperature Range on your Transmitter, you will have to figure out on your own.

Stu....
 
The temp. range for the transmitter is something like -40 to 160. It tells you in the manual which I dont have in front of me.
So all I have to do now is find the min. and max of the AB 1746 N1041 card?
 
Let's take a little bit of a step back to that user manual.

The 1746-NIO4I is a combination module with two Input channels (configurable for voltage or current mode) and two Output channels (current mode only).

It's very easy to get turned around in that user manual because it covers several different modules with both input and output channels. The The other values cited above are for an Output channel.

Page 4-6 of the User Manual says that on the 1746-NIO4I module when an Input channel is configured for 4-20 mA current loop mode:

4 mA = 3277 counts
20 mA = 16384 counts


If your RTD transmitter really puts out 4 mA for -40 degrees and 20 mA for 160 degrees, then you have all the information you need to use the SCP instruction.
 
Sorry for the delay in responce but I am having a difficult time with the transmitter i am using...I think its not compatable w/ the card. I am getting a constant 22mA.
I will let you know the outcome when I resolve this issue.
Thanks again
 
I am getting a constant 22mA.

that's commonly called an "upscale" indication ...

usually when a temperature transmitter does that, it's a "safety" type signal to let you know that the thermocouple/RTD sensor is disconnected from the transmitter ... check your wiring ...
 
It was my wiring...I needed a 3 wire RTD instead of a 2 wire.
Also, I needed a +24vdc to the card,and -24vdc loop threw the RTD transmitter and back to the card.
Just needed a little troubleshooting.
Thanks again guys
Tim
Your paramiters seem to be working fine.
 

Similar Topics

Hi all, I am looking for a temp. transmitter that can be installed in a 1" or 1-1/4" copper pipe. I recommended a clamp on type to my client...
Replies
11
Views
1,924
Anyone have any suggestions on good ones or websites to look? Its going to be inside.
Replies
4
Views
1,411
Hello, I'm working with a 1747-NI4 analog input module (for the first time) on a SLC503 processor. I noticed in the IO configuration within...
Replies
13
Views
4,709
I am going to use a little Dwyer/Love controller to modulate some dampers. There is a outlet and mixing damper that i want to move together. Can i...
Replies
1
Views
1,764
Problem: Our PLC can only output 4-20mA, but the actuators it needs to control, modulate based on a 0-135Ohm signal. Buying 4 or 8 individual...
Replies
7
Views
219
Back
Top Bottom