OT Recorder Replacement

[John Gaunt]

The 0.01 deg C resolution is required only in the PLC for multiple loop advanced control.

The backup readout device only needs a 1.0 deg C resolution.

 

[Gummit]

It sounds to me like you just need a digital panel meter with a selector switch. I don't know if you can get a suitable switch up to 36 positions but you certainly can for 12. So, you could have 3 panel meters and 3 switches.

The Tracker 220 panel meter has a high impedance and the break sense detection can be switched off.

Take a look here to see what I'm talking about.

Rob

 

[John Gaunt]

Thanks Rob (Gummit),
The panel meter and selector switch would serve the function OK.
I would probably use two panel meters and two switches for my current project to monitor 24 thermocouples.

My only reservation is that it is a bit old fashioned looking.

The ideal would be like a modern recorder that can scan through its channels a few at a time displaying their values and allow the operator to lock onto a particular group if he wishes. I just don't want the recorder part.

 

[danw]

What about a multiplexor to automatically cycle through to switch, in turn, one of 8 field signals to a single output?

Precision Digital's PD 118

http://www.predig.com/products/prodSpec.asp?ID=PD118

Dan

 

[Brian123]

Thanks Rob (Gummit),
The panel meter and selector switch would serve the function OK.
I would probably use two panel meters and two switches for my current project to monitor 24 thermocouples.

My only reservation is that it is a bit old fashioned looking.

The ideal would be like a modern recorder that can scan through its channels a few at a time displaying their values and allow the operator to lock onto a particular group if he wishes. I just don't want the recorder part.

Have you considered setting up another PLC (or FieldIO type device) and just using an HMI to display the temperatures? I haven't used AD's TerminatorIO stuff, but it looks like you could connect that directly to an HMI to display the data. The drawback to this type of approach will be cost. A couple of panel meters and switches will likely be far cheaper.

Brian

 

[John Soltesz]

Thanks Rob (Gummit),
The panel meter and selector switch would serve the function OK.
I would probably use two panel meters and two switches for my current project to monitor 24 thermocouples.

My only reservation is that it is a bit old fashioned looking.

The ideal would be like a modern recorder that can scan through its channels a few at a time displaying their values and allow the operator to lock onto a particular group if he wishes. I just don't want the recorder part.

I doubt if you can get a 24+ ch recorder (display only doesn't exist I would say, no market) for under US$6k. A small PLC with T/C input cards and display maybe US$3-4k. A couple switches and meters (a price wag only) of under US$2k. If your goal is to not have a backup display in the future go with the "old fashioned looking" meter display. Let the customer make that decision. Give it your best shot of course but don't let the archaic view of the customer take away from a good working project.
Maybe this is why the circular chart is available in the digital form on display screens. The old operators liked them is my guess.

 

[surferb]

This is very good advice! At some point, you just need to present the options with your recommendation to the customer/boss and see what decision they come up with. IMO, people may begin with a requirement from left field, but then are usually open to rational alternatives once given the options with reasons. It baffles me when integrators bend over backward and implement weird things to take a customers request litterally, when the customer didn't know there was even an issue or a better way.

I doubt if you can get a 24+ ch recorder (display only doesn't exist I would say, no market) for under US$6k. A small PLC with T/C input cards and display maybe US$3-4k. A couple switches and meters (a price wag only) of under US$2k. If your goal is to not have a backup display in the future go with the "old fashioned looking" meter display. Let the customer make that decision. Give it your best shot of course but don't let the archaic view of the customer take away from a good working project.
Maybe this is why the circular chart is available in the digital form on display screens. The old operators liked them is my guess.

 

[OkiePC]

I still like the idea of trending the PLC data with an HMI capable of trending and storage.


If redundant thermocouple interpretation is a requirement, so you have an alternate record if a the PLC fails, then you may want to look at a group of these with an el cheapo panel mount PC running their software.

Just alternate suggestions, I have only used a Madgetech single channel pressure logger once, but the pump vendor who provided it swears by them.

I would probably go with redundant TC cards in the PLC to have redundant recordings in the even of a TC input point failire. And I would probably try to use the HMI with storage method, unless the process can run without the PLC, before investing in the expense of a standalone capable TC logger.

Paul

 

[John Gaunt]

Thanks OkiePC,
The logger with a panel PC looks like the sort of thing I need.

Somebody I know has suggested I could do something similar with a touchscreen that supports MODBUS or similar and a low cost I/O system to input the thermocouple readings.
Has anybody had experience doing something like that ?