OT Recorder Replacement

John Gaunt

Member
Join Date
Nov 2004
Location
Tasmania, Australia
Posts
362
We usually supply a 24 or 36 point recorder on our PLC panel to display the values of our more important R-Type thermocouples.

We have recently started using paperless recorders as the paper and ink replacement was always a problem.

Really what we need is the ability to display the 24 or 36 thermocouple readings nicely. Probably optionally scrolling through them in groups or holding a particular group.

Something like the paperless recorder, but without the recorder would be ideal.

We need something of quality that doesn't interfere with the signals wired in parallel to the PLC.

Does anybody know of something that might do ?
 
Hi John, Have you ever thought of a software to gather thermocouples data from your plc to a PC, or have your ever thought of a HMI terminal where you have a trend with the info you want. These are the two options i think you can use, of course there are others but these are mine.
 
I'm not sure what you mean. We use the web view mode of the Honeywell paperless recorders where the recorder screen shows up on anyone's PC in a web browser. At an office desktop, one can scroll back or forth, zoom in-out, print a screen, mark the chart, look at the message log, whatever.

But the operators use the screens locally, too, so paperless recorders work well.

Is what you're asking for a blind 'front end' box (amplifiers, A/D, buffers, interface) that collects the data, but has no screen?

Or an HMI software package that talks to the PLC and grabs data from it?
Dan
 
Sounds like OP's referring to a hardware device based on this,

"We need something of quality that doesn't interfere with the signals wired in parallel to the PLC."

A software based recorder with a web view is a great way to go given his requirements. It has the added benefit of easily supporting many more "pens" and being able to accurately analyze the data.

danw said:
I'm not sure what you mean. We use the web view mode of the Honeywell paperless recorders where the recorder screen shows up on anyone's PC in a web browser. At an office desktop, one can scroll back or forth, zoom in-out, print a screen, mark the chart, look at the message log, whatever.

But the operators use the screens locally, too, so paperless recorders work well.

Is what you're asking for a blind 'front end' box (amplifiers, A/D, buffers, interface) that collects the data, but has no screen?

Or an HMI software package that talks to the PLC and grabs data from it?
Dan
 
Sorry, I obviously was not clear enough.

I use S7-400 PLC's and Citect SCADA running on multiple PC's.
The recorder is an historical requirement in the event of failure of the PLC. The users do not yet feel comfortable enough to not have any backup.

As an alternative to a real recorder I have got acceptance of a paperless recorder as their main use is to read the digital values displayed. The recorder normally only shows a mess of perfectly parallel lines.

Now I would like to go one step further and only provide a digital display of all the 24 (or 36) values. So far I have not found a suitable device.
 
Doesn't the paperless recorder have multiple screens, like an HMI might?

We use trends with tiny digital readouts on each trend screen (not our actual screen shots, I had to steal these from a pdf manual I have at home, but very similar):

trend_with_digitals_Screen.jpg


or the operators can switch to large digital readouts:

16_DPMs.jpg
 
The PLC and Citect SCADA provides all the 3D Graphics representing the plant and sophisticated auto ranging trends.

What I am looking for is a physical device to provide backup readouts of some important temperatures. As low cost as possible but it must not interfere with the PLC thermocouple readings.

My eventual aim is to elliminate this device entirely on systems in the future.
 
We have an older Yokogawa 20+ ch recorder that has a single display that scrolls through all the programmed channels. It stores data internally and the operator can send the data to a floppy if needed. I don't know what kind of price it was or what the newer lines have. Honeywell has I think a 30 ch video display/recorder like what danw shows above. None of these are real inexpensive when you go to 30 channels and all record to some extent. Another way is a PC with a USB or ethernet I/O card that would just display. This could be a bit clumsy.
It is true not all recorders can leave a T/C line unaffected. If you can shut off burnout detection that would help. I am assuming the S7's have T/C input cards and not T/C transmitters to an analog card.
 
Are the thermocouples going to the recorder first then retransmitted to the PLC? Or, do you somehow split the signal to both at the same time.

George
 
Weve used Yokogawa paperless chart recorders on some of our projects. They go up to 40 channels, display nicely and can do math & modbus master/slave.
Theyre also really easy to configure and are super reliable.
The only problem is theyre not cheap!
 
John Gaunt said:
What I am looking for is a physical device to provide backup readouts of some important temperatures. As low cost as possible but it must not interfere with the PLC thermocouple readings.

There's a whole catetory of devices known as 'dataloggers' that are typically blind (no display), storage (flash), varying numbers of inputs and types of inputs and data storage rates.

I have no experience with any, other than knowing that they're out there and probably offer what the capability you're looking for.

Dan
 
Thanks John Soltesz and George Graziano,

The S7-400 input cards we use are the best available for S7 and are set up for thermocouple linearisation with cold junction compensation. We always turn of any burnout detection on the recorders we use.

We run the thermocouple wiring into our control panel to thermocouple terminals near the recorder and PLC. From the terminals we run in parallel to both the Recorder and the PLC.

We work to a resolution of 0.01 degrees C at 1200 degrees C in the PLC and don't find any problem when using good quality recorders.

As the recorder is only used to digitally display temperatures in the event of a PLC failure I am looking for a low cost HARDWARE device. However, it must NOT interfere with the thermocouple signals.
 
Funny how I can read something and misinterpret it. John, you were clear that you need 'readouts' of temperatures, not logging.

The dataloggers I've heard of are good at storing data, generally not at displaying data., relying on after-teh-fact transfer of data to a PC for viewing data.
I'm stuck. I really don't know of anything that does multiple digital readouts, especially to the resolution and accuracy that you're seeing with the recorder you're using. 1/32 DIN PID controllers don't have the display resolution. Low end thermocouple panel meters only display whole number degrees. Thermocouple panel meters that can display a decimal point are over $300/point, at which point, a recorder is lower cost. The meters I I've used can't do 0.01°C, only 0.1°C resolution.

Dan
 

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