1756-OF8 Analog Output Module Question

sthays10

Member
Join Date
Jan 2006
Location
Washington
Posts
84
Hi All,

First off, thanks for all the previous help. Now I have another question.

I am using a 1756-OF8 to send a 0-10V signal to an actuator. The position of the actuator is 100% open at 10V, and 100% closed at 0V. Any voltage in between will open the damper to the relative percentage (ie, 5V will open to approx. 35-40%). I am having difficulty getting the outputs to show up correctly.

I have configured channels 0, 1 & 2 for each of the 3 actuators. The output range for the module is -10 to 10V. Under scaling,

High Signal High Engineering
10V = 100
Low Signal Low Engineering
0V = 0

I have tag ACTUATOR_1_OUT aliased to output channel 0.

When I go through the calibration, I get 0V and 10V as I should. However, when I run my program, even though ACTUATOR_1_OUT is 100, I measure 1V on my multimeter.

I appreciate any and all advice.

Thanks

Steve
 
Look under the module properties, and go to the limits tab. Adjust the upper limit to your new engineering high.

The default clamps the output at 10, so 10/100 = 1 Volt.
 
Actually, I'm not familiar with how (or really, what) a PID is. It's for a damper (instead of a valve) in a ventilation system. If the airflow is higher than desired, it will open, and lower vice versa. I just used simple greater than/less than instructions for the most part, with some added diagnostics/features.

I know the CLX is probably way more power than I needed, but in a time crunch, you revert to what you know. How does PID work? I know there is probly a good tutorial on this site, just haven't been able to find it searching.
 
Do a search on this site, for PID with Ron Beaufort (spelling) as the author. He has broken it down quite nicely, along with Peter Natcheway (spelling).

Basically a PID is propotional integral derivative control.

Let's say you have an airflow of 6 SCFM that you want to maintain. If you have just. 6 SCFM would be the setpoint, and what ever your current airflow reading (say 4 SCFM) would be the process value.

The proportional part is very straight forward, in that you take the error (SP-PV) and multiply it by a constant you give it, and the output (damper) opens based on that difference.

The biggest problem with P only control is that the PV will either ossicalte, overshoot and undershoot the SP, or never make the SP.

The integral will attempt to make up the error over time to affect the output, and the derivative will look at the rate of change to affect the output.

Together the 3 terms are used quite effectively to control contious processes like airflow, temperature, motion, etc.

You should look into it if you want to maintain closer to your setpoint.
 
Good day, I have a similar problem, am using a 1756-OF8 output module with range -10 - 10V. How do I output 0 - 10V Or 0 -5V?

Upon changing my engineering to 0v=0 -10v=100 and getting 20v at the channel.

Any help will be appreciated
 

Similar Topics

I am facing an issue module 1756-OF8 is showing the minor fault = recoverable in the module info.How can i reset it?
Replies
0
Views
1,706
PN1651 - ControlLogix 1756-OF8/B modules may exhibit spurious channel 4 through 7 faults. Rockwell just released this and we have an upcoming...
Replies
6
Views
981
Hello, I am trying to do a very simple task (just checking to confirm that all channels work) with a 1756-OF8. However, when I add the module in...
Replies
4
Views
1,156
Electrical simpleton here, so show me mercy. Plant previously had a 4-20ma valve that was controlled via pneumatic controller with a P/I. Now...
Replies
8
Views
3,091
Hello everyone! I am having some issues wiring 3 Proportional valves. I am connecting the valve position reference to a 1756-OF8 AB card in a...
Replies
2
Views
1,572
Back
Top Bottom