HART Transmitter with separate terminals for HART and 4-20mA

[123MB]

Hi All

I need to confirm the compatibility of a HART transmitter with a HART analog input moodule.

The complication is that the transmitter has two separate set of terminals for 4-20mA output and HART. It does not have a single pair of terminals for 4-20mA/HART.

This may be a stupid question but can I connect the HART terminals in parallel with the 4-20mA terminals and send them to the 4-20mA/HART analog input channel?

Has anyone come across this situation before?. Thanks.

 

[thebard3]

What is the device you describe? I can wager a guess that the HART protocol is still part of the 4-20, and maybe the separate HART terminals are RS-485 or something like that. The 4-20 terminals could also be separate analog and the HART terminal the conventional analog/HART, but I don't know why anyone might need that. Without more information I'm just guessing.

Brad

It's all okay as long as it's okay.

 

[123MB]

It's a flowmeter, GE Panametrics Z1G.

See attachment, this is the best info we have. Naturally bench testing would reveal all, but we don't have that luxury, as usual.

 

[thebard3]

That drawing isn't high enough resolution to make out all of the descriptions, but I think that the HART NET (+) and (-) is probably a conventional 4-20 HART protocol, but it's listed as an option. Also this device seems to have 2 output channels, so a single analog HART output wouldn't support that, but maybe the HART protocol provides data for both channels? Can you provide manufacturer info?

Brad

It's all okay as long as it's okay.

 

[123MB]

Thanks for your responses mate..

Here's a high res of the terminals:

The manual that this has been taken from is here:

https://www.gemeasurement.com/sites...eter_panaflow_z1g_z2g_usermanual_910-321a.pdf

Unfortunately this is all the info I have.

I have a support request in with GE but it's already been a week and I'm losing hope

 

[thebard3]

Okay, as far as your question "Can I connect the HART terminals in parallel with the 4-20mA terminals and send them to the 4-20mA/HART analog input channel?" I'll say emphatically NO.
Use the HART (+) and (-) terminals and you should be good to go. If that doesn't provide the 4-20 mA signal as well, then I'd say it's not really a HART connection. BTW, never connect the shield at both ends, so don't use the 'optional shield' connection. It's best practice to only connect the shield to a good panel ground, and keep it isolated the rest of the way out.

Brad

It's all okay as long as it's okay.

 

[danw2]

My best guess.

paper pg 46 (pdf 56) of the manual you provided the link for says
Digital Communication
Optional: HART

I'm guessing that the dual 4-20mA analog outputs (AOUT A + or -, AOUT B + or -) are not HART enabled, but are 4-20mA only (HART chips cost money).

Those who specify the HART option get the single optional HART on the (optional) Digital Comm options card.

The drawing you provided lists HART on the left side as OPTIONAL, and describes the terminals as HART NET (+) or (-), "HART NET" being a unique GE-invented marketing term.

 

[123MB]

I see

Thanks all.

So, each channel on my input module is intended for 1-off 4-20mA/HART transducer. The documentation doesn't specifically say anything about the module being suitable for 4-20mA/HART, HART NET, multidrop or point to point.

Can I connect it to the HART NET + and HART NET - terminals, and expect it to work? But it may or may not provide me with the 4-20mA on the input?

I am confused.

If anyone is nice enough to follow the rabbit down the hole further, my input module is a 1734SC-IE4CH - Manual here:

https://www.spectrumcontrols.com/media/1452/0300257-01_a1-manual_1734sc-iexch.pdf

Thanks again.

 

[thebard3]

The HART card should be compatible with the analog signal. It just won't have the HART data imposed on it. As with any other analog device, you will get a linear process signal. See tables 3-4 and 3-5 depending on your module, It shows the data table size needed, depending on the data you are expecting. Since you are using analog data only, see figure 2 for the data table area your process data will appear. It is raw, unscaled data, so you may wish to use a scale function block to turn it into engineering units.



Brad

It's all okay as long as it's okay.

 

[123MB]

So in other words, you don't see an obvious way (without testing) to get the HART data out of the flowmeter with this combination? Even if we had to ignore the 4-20mA?

 

[thebard3]

Sorry, I guess I was believing that you didn't have the HART capability with the flowmeter. If it's HART enabled, you should get BOTH 4-20 mA analog data and HART data imposed on it. The Spectrum manual shows the data file where the various parameters will be populated.

Brad

It's all okay as long as it's okay.

 

[danw2]

>Can I connect it to the HART NET + and HART NET - terminals, and expect it to work?

You can expect connections to the flowmeter's HART NET (+) and (-) to provide a 4-20mA output signal (presumably ranged in the flow meter setup), with the device's HART slave functions silent, awaiting communications from a HART master.

>But it may or may not provide me with the 4-20mA on the input?
If you get HART, you get a current signal. A 4-20mA will be there, assuming my former conjecture on what HART NET (an undefined GE marketing term) means, which I speculate means the HART option with a current loop.

> get the HART data out of the flowmeter with this combination?
That card will read the HART data from the flow meter in a point-to-point configuration. How you get the data out of the I/O card is another thing.

The first section in the HART I/O card manual is all about requirements for some form of digital communications card that connects to the HART I/O card, presumably to get the field data out of the HART I/O card.

Assuming that you meet the digital communications hardware and setup requirements AND the setup requirements for the HART I/O card, it will presumably get HART data out of the flowmeter.

 

[roydm]

There are probably ways to transformer couple the HART in series with the 4-20
If you don't get the HART imposed on the analog with a second pair of wires, just hook it onto a second HART input.