1756-HSC Need to use as both an encoder and for frequency

[rdlandry]

I need to basically combine two modes. I need an instantaneous rate, which would typically use "Frequency" mode. However, I also need to know direction of flow, which would typically use one of the two "Encoder" modes (I have two sensors offset by 90 degress). The problem is that the "Encoder" modes seem to only work as counters. I need them to work as instantenous rate. Can this be done?

We were able to do this using the SLC500 HSC module. We would set it up for encoder mode and it would give us a rate of either +/- a value. A value of 500 would indicate 500 gallons flowing in one direction. A value of -500 would would indicate 500 gallons flowing in the opposite direction.

When I set up the Controllogix HSC card in the exact same manner, it only gives me a counter instead of a rate.

HELP!

 

[MichaelG]

What are you connecting to? Part number if possible
What version of RSLogix 5000 are you using?
HSC A or B?
Is the HSC on the processor main rack and what connection mode are you using?
How did you set up the HSC card? Especially the Operational Mode and Storage Mode

 

[rdlandry]

Hey, Michael, thanks for your reply.

I'm not sure of the model number of the sensors. I believe they are made by Halliburton. The application is for measurement of water flow in a pipe.

RSLogix5000 version 16.
HSC B
Card is in a remote rack.
Communications protocol is Controlnet.
Set up in Encoder X1 mode (mainly because that's the way
it worked using the SLC500)
Storage Mode: No Store Mode

If I put it in Frequency mode I read the correct frequency. So I feel fairly confident that it is wired correctly.
But if I am correct, frequency mode ignores Channel B. Therefore, I wouldn't be able to tell flow direction. This is critical.

Thanks in advance for any suggestions. I find it very hard to believe that this application works for the SLC HSC, but not for the CLX HSC.

 

[MichaelG]

do you have the latest manual? It says it does what you want

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1756-um007_-en-p.pdf

The 1756-HSC/B module also offers the convenience of showing directional
frequency by using any Counter mode. If the count value is increasing, the
frequency is positive in the Totalizer tag. If the count value is decreasing, the
frequency is negative in the Totalizer tag.

You may have a HSC/B firmware or RSLogix 5000 Software version problem.

 

[rdlandry]

I think you may be correct. I am using Logix Version 16. The HSC is a version B, but when I added it to my I/O config it defaulted to series 1.x.

Looking at the manual, it appears that I need to be in Version 18 of the software and using series 3.x of the card.

This is a problem for me because we currently use the SRM redundancy modules, which are only supported thorugh RSLogix version 16.

In fact when I open my I/O tree for the HSC, there is a PresentValue and StoredValue, but no Totalizer value.

Do you think it is possible to use a firmware upgrade of the HSC card to version 3.x and work in version 16? I am going to do a little digging on the Rockwell support website.

Anyway, I appreciate you pointing out that quote to me. At least now I know the card will do what I want it to do. But it may not do it in my current software/firmware revision.

 

[JeffKiper]

Think of instantaneous rate as rate of change. Setup a new periodic task to run at XX ms. Use that to calculate the rate of change in the HSC. 2 bird 1.5 stones

 

[MichaelG]

Check out appendix D - Module History in the manual

If you go JeffKiper route for using the changes to calculate the "speed" then have a read of a preferred velocity calculation method
http://www.plctalk.net/qanda/showthread.php?t=48328