Rosemount 848L replacement

[Rob Wallace]

Is anyone aware of a digital multiplexer to replace the now discontinued Rosemount 848L?
I was suprised to learn that Rosemount was no longer manufacturing the digital multiplexers any longer. A great product I thought.
I cannot find another similar FF product on the market, is anyone aware of a FF digital multiplexer??

Thanks Rob

[rezabejd]

Excellent question. Too bad this product went away. Stonel makes a 2 DO / 2 DI module and P+F has a few products I believe. Try "End User Resources" at fieldbus.org > registered products (http://www.fieldbus.org/index.php?option=com_mtree&task=search&Itemid=324&ffbstatus=Registered&ffbmfg=&ffbcategory=Analog+or+Discrete+I%2FO+Block) and search on "Analog or Discrete IO Blocks".

Be sure to look closely at the European solutions as I hear some include a capacitive coupling to ground (??) which could create a signal ground or shield ground where you didn't expect it . . . maybe someone from P+F or Stahl can clarify. You may just have to mount it differently.

[Mike ONeill]

Stahl have a couple of digital multiplexors for connection to high power trunk: 9413/21 and 9413/28. They allow 8 dig in contacts/NAMUR prox plus 4 dig out solenoid drivers (24V, 30mA switching/15mA holding). Software is DI/MDI/DO/MDO/FREQ/CI/LOGIC.
9413/28 is 2-wire device but needs 190mA@28V, 17V minimum (doesn't have a 'tick mark' as FF standard devices have to work down to 9V)
9413/21 is 4-wire device and takes 12mA, has FF tick mark.
Both have regular ground and capacitative ground connections - your choice.
These units are nice in that they are not limited to only ultra-low power, high cost I.S. solenoid valves and we can package the units as an FF valve island if you wish.

[tklatt]

The P&F valve coupler FD0-VC-Ex4.FF can also be used as a 8 DI box (http://www.fieldbus.org/index.php?option=com_mtree&task=viewlink&link_id=1132&ffbstatus=Registered&Itemid=324). This device is completely intrinsic safe and the shield terminals are connected to the housing (which must be grounded within a hazardous area).

[rezabejd]

The P&F valve coupler FD0-VC-Ex4.FF can also be used as a 8 DI box (http://www.fieldbus.org/index.php?option=com_mtree&task=viewlink&link_id=1132&ffbstatus=Registered&Itemid=324).

Thomas - why does the profile say " one DI "? Maybe this is DD-speak for saying it has DI capability?

Thx
John

[Rob Wallace]

Thomas, does P & F manufacture a valve coupler that can drive a 24V solenoid? The valve couplers I have worked on are IS, bus powered and only capable of driving special low power solenoids.
Our application is non hazardous with external 24V supply available.
Rob

[Mike ONeill]

Sounds an ideal application for the Stahl 9413/21.
If you need to find the right contact or relevant sales office within Stahl, please look up www.r-stahl.com

[IanVerhappen]

StoneL also make a DI/DO product and their product claims to be powered by the H1 segment so you do not need another power supply in the field to wet the contacts. With StoneL you have to watch for electrical approvals as they are limited. I also think that Buerkert make a unit - but that should show up on the link John suggested. Lastly, at one time Smar made a product for DI/DO that also had I believe 50 rungs of relay ladder logic capacity.

I am sure that one of these products will do the trick.

[jberge]

Discrete I/O should be eliminated as far as possible:
Control valve limit switches: No longer applicable. Built into Fieldbus positioner
On/off valve solenoid and limit switches: Use Fieldbus valve actuator or coupler with integrated solenoid and limit switches instead (see link below)
Electric actuators (MOV): Use Fieldbus electric actuator instead
Process switches: Use entry tier Fieldbus transmitters instead
Motor controls (pumps, fans, agitators, conveyors etc.): Use PROFIBUS-DP drives and starters

With this DI/DO can be drastically reduced

For FF on/off valves see these solutions:
http://www.topworx.com/valvetop/vc_dxp_info.html
http://www2.emersonprocess.com/en-US/brands/fieldq/FieldQ_product/Pages/index.aspx
They eliminate 1 DO and 2 DI plus provide diagnostics making engineering and predictive maintenance easier

I have a white paper that discusses DI/DO for FF in greater detail

Cheers,
Jonas

[Manjit Singh]

Mike

1. Firstly I do not understand what does it mean by 24Vdc (4 - wire). Will be it possible for you to explain?

2. Secondly I am intending to utilise low power solenoids either 0.8W or 1.7 Watts to be driven by the Digital Outputs of this IO Multiplexer. I understand that the maximum current per output is 100mA. Does this sound right?

[Mike ONeill]

Yes, 4-wire means that we have 2-wires for FF comms and 2-wire wire for local 24Vdc power. FF and power are isolated from each other and the FF connection can be I.S. or high power trunk. As far as the FF H1 is concerned, this unit looks like a normal device @9V and 12mA, and has the FF Tick Mark. The 24V dc is from any local source. If you are doing a lot of these, we can do you a ‘valve island’ hazloc box with AC/DC power pack …

We also have a 2-wire version in which we take power from the H1 bus just like a ‘normal’ device, but because we are driving outputs, we need to take rather more current than normal (up to 380mA) and we need 14V to make it work – FF don’t actually have a standard for this (field devices are supposed to operate at 9V) and so we don’t have any FF Tick Mark.

The solenoid driving current is 30mA and this meets requirements of 8314 ASCO valves. 30mA starts them, 15mA is sufficient to hold them ON. ASCO are probably the world’s largest suppliers of solenoid valves. If you are looking at other makes, the key parameters are actuating current and coil resistance. Some valve datasheets can be misleading if they just quote an operating current at nominal line voltage. For example, coil resistance of 340R plus cable resistance of 20R fed from an I.S. supply at 23.5V and 340R (ours) gives total current of 23.5/(340 + 20 + 340)= 33.5mA. Coil resistance does vary with ambient temperature, and you really want a 12V valve with a 350-400R coil to match with a 24V supply and 350R source resistance.

[jberge]

I just want to make sure that all are aware that you can now buy Fieldbus on/off valves. That is, you don't need to put remote-I/O multiplexers in the field any more - no need to send people into harm's way to check on I/O. That is, instead of running three pairs of to each on/off valve (solenoid and two feedback limit switches) one pair of FF wires can go to 12 or so valves. Imagine the wire reduction... Moreover, these on/off valves provide diagnostics and integrate into intelligent device management software. See for instance:
www.fieldq.com
amd
http://www.topworx.com/valvetop/vc_dxp_info.html

I also have a long white paper on discrete devices with fieldbus. It also covers electric actuators / motor operate valves (MOV)

[makanzysmith12]

We also have a 2-wire version in which we take power from the H1 bus just like a ‘normal’ device, but because we are driving outputs, we need to take rather more current than normal (up to 380mA) and we need 14V to make it work – FF don’t actually have a standard for this (field devices are supposed to operate at 9V) and so we don’t have any FF Tick Mark.

The solenoid driving current is 30mA and this meets requirements of 8314 ASCO valves. 30mA starts them, 15mA is sufficient to hold them ON. ASCO are probably the world’s largest suppliers of solenoid valves. If you are looking at other makes, the key parameters are actuating current and coil resistance. Some valve data sheets can be misleading if they just quote an operating current at nominal line voltage.