Heater current monitoring

[rdrast]

I use these current sensors from AD. Been using them for years now to monitor heaters, zero issues. If you are short on IO points, you can always use something like IO-Link masters/hubs to terminate the switches to.

 

[JesperMP]

I use these current sensors from AD. Been using them for years now to monitor heaters, zero issues. If you are short on IO points, you can always use something like IO-Link masters/hubs to terminate the switches to.

He wants analog signals so that he can display the values to the operators.

 

[Manglemender]

Our factory is now covered in little self powered sensors that wirelessly report the current every 10 seconds via a local concentrator. Maybe something similar would suit:

https://www.centricabusinesssolutions.com/energy-solutions/energy-management/energy-insights-solutions

Nick

 

[RoTaTech]

Jesper: No, I meant that whatever analog data collector would read the CTs, could connect with Profibus to the controlling PLC.

 

[JesperMP]

Jesper: No, I meant that whatever analog data collector would read the CTs, could connect with Profibus to the controlling PLC.

But any device that can collect the data from the 70 CTs would take space in the same way as a PLC chassis.
As you wrote before:

Per the bunch of analog cards - no physical room for another chassis.

Unless the device or devices are panel mounted it will take space on the mounting plate.
Or do you mean that there is some space on the mounting plate, only less than for a full 505 chassis ?

 

[Rson]

Per the Ethernet connection - no, our current PLC does not support it.

Per the bunch of analog cards - no physical room for another chassis.

Per the CT with switch - no, we do want to display the current -- each zone may have multiple heaters, so if the zone had three heaters and should draw (e.g.) 30A and one burns out, we would see only 20A. I know the on/off CT would notify that, but staff is accustomed to bouncing needles on meters.

And on that note: Measuring the overall total draw will not work as each zone can cycle on/off independently.

But I thank you for the thoughts; I will check on two of your suggestions.

Why, though? If you just wired a CT switch up to each heater, you can create a fault condition for each heater. If the heater is on and you don't see the current switch on after a few seconds display a fault on the HMI.

I think the digital I/O solution would be much cleaner and less expensive than trying to do all of those with analog. Calculating all of those ampere draws / etc. seems needlessly complicated IMO.

 

[Nova5]

Motion seconded.
Newer PLC is most likely smaller than the old S5, allowing enough room for analog modules or it will be able to communicate on modbus, profibus or whatever protocol the choice of CT can put out.
Assuming you're sticking with Siemens it would need to be an S7-1500 CPU for analogs as the 1200 can't support enough modules. I like the ET200SP mounted CPU's as they're cheaper.


That said... I do like that multiplexer idea. It's going to be slower but it's going to alarm faster than a gauge.

CLX and SLC are abouthte same width. I think the SLC is a shade taller..

 

[RoTaTech]

Or do you mean that there is some space on the mounting plate, only less than for a full 505 chassis ?

Correct, Jesper. The chassis is near full, but I can allocate panel space.

 

[JesperMP]

With Siemens ET200SP you can have 8 analog inputs per module, each 15 mm wide.That is relatively compact, and you can hook it up to the 505 via profibus. There are others in the same style, Beckhoff, Wago ..

These day the problem may rather be what can be sourced that will not take until next year to arrive.

I would also consider replacing the 505 entirely.

 

[RoTaTech]

Jesper: I shall investigate those, as long as I can source CTs with 4-20mA output. And yes - delivery times on some of these components is a silly long time!

re: changing out the 505. They are not wont to do that; I have suggested other options, but the 505 platform is still available from CTI and it is the desired path.

 

[rdrast]

He wants analog signals so that he can display the values to the operators.

I did see that, but honestly see almost no point in duplicating meters that nobody looks at anyway.



I have one of those switches on each leg of 3 phase heaters, and can still monitor for burnout, stuck contactors, and shorts easily, with no interpretation required by the operators/maintenance. Just read the alarm

 

[JesperMP]

I did see that, but honestly see almost no point in duplicating meters that nobody looks at anyway.

You are not wrong.
Especially for heaters, once energized, it is always the same current that flows. So there is not much variation to observe.

I have one of those switches on each leg of 3 phase heaters, and can still monitor for burnout, stuck contactors, and shorts easily, with no interpretation required by the operators/maintenance. Just read the alarm

We do something similar.
Carlo Gavazzi DIA 53S72420A

You can connect 3 in series to get 1 signal to the PLC "all phases OK".

 

[AustralIan]

ABB CMS-700 might be a good option, but you would need also something to convert it from Modbus (485 or TCP) to profibus.
It has a small CT which clips on the top of a miniture circuit breaker, and you can daisychain them back to the main unit which transmits it as modbus.

 

[RoTaTech]

I thank you all for the suggestions

Now to wade through and choose one, and post back after we choose.

I do like the suggestion of ditching the meters/analog displays, and just use presets current limits and alarms. I am going to propose that as a cost-saving measure since - as was mentioned - they are rarely viewed for the the thousands of $ it would cost.