HART Communicator does not connect with transmitter

S

Thread Starter

sonny

In a gas plant.

We use the HART COMMUNICATOR to interrogate with the transmitter while carrying out PM or CM. This is a process plant, the transmitter are connected in a vessel or tank to control or monitor level of temperature or a control valve. when you hook-up your HART COMMUNICATOR it will display "NO COMMUNICATION".

when you don't 24VDC to the transmitter, it will show "NO COMMUNICATION". On further troubleshooting the auxiliary room end to the field will have 24VDC (4-20MA).
 
J

Jonas Berge - W

Here are a few points you can check:

Is the device powered on? Verify local display
-Check polarity

-Is auxiliary power required?

-Connection in the system-end depends on the device being loop-powered or separately powered

Is sufficient power supply available (check the voltage at the device terminals, at 20 mA)?

-Measure DC with digital multimeter (DMM)

-Note that 4-20 mA can work at low voltage that causes HART to fail

-Some devices require only 10.5 V, others require 19 V or maybe more. Each device type is different. Check the device manual.

-A critical point especially when safety barriers are used or if multiple receivers are connected in series (indicators, signal conditioners, trip amplifiers, chart recorder, DCS/PLC, wireless adapters, etc.)

-Check for poor connections or corroded terminals at device and junction boxes etc.

-Ohm's law applies: the supply voltage must exceed the minimum power needed by the device plus, series receivers, plus sufficient voltage to overcome loop resistance

Is there ripple/noise on the power supply?
-The 4-20 mA negative is usually ground/earth, so it must be 'clean'-Note that 4-20 mA can work in spite of ripple/noise that causes HART to fail

-If noise is present, check the installation: twisted pair, shield, ground/earth, separation from AC power cables (particularly drives).Check inside housing of AC powered devices like magflow meters where signal and AC wires may be rolled-up together

-Measure AC with digital multimeter (DMM) and also check with oscilloscope

Is shunt resistor (>230 ohm) present (for transmitter)?
The handheld shall be connected on the device-side of the shunt resistor (not the power supply side)

Is HART filter required by the control system?
Is safety barrier used? If so it must be compatible with HART protocol

Compatible HART version? Host s (handheld field communicator, laptop software, control systems, intelligent device management software, calibrator, signal converter) designed for HART version 5 and 6 do not work for HART7 (no forward compatibility), but systems designed for HART version 7 also work for version 5 and 6

Conflict with other primary or secondary master (DCS, modem/interface, multiplexer, signal converter, wireless adaptor etc.)?
-Some adapters and converters etc. can be configured as either primary or secondary master

Correct device address (usually zero, but not in multi-drop mode)?
-For WirelessHART adapter the address may be higher than 15. Check the manual

Cheers,
Jonas
 
K

kenberberich

Not trying to be stupid here but is the device Hart compatible?

I have had problems on startups with the manufacturer slipping in a modbus transmitter and no one catching it until I did the startup checks.

Also most of the time if the hart does not see anything the Error will be "NO DEVICE FOUND".
 
R
It's possible that the control system doesn't have enough impedance for the HART signal. some input cards I have seen are only 50 Ohms. A clue would be the Voltage you see across the transmitter terminals 23 Volts at 0% would suggest the impedance is 250 any more than 23 would indicate < 250 Ohms.

The HART signal wants to pull the lines up and down, without enough resistance in series it has difficulty. The resistance doesn't have to be 250 Ohms it will work with more or less. a 220 or 330 Ohm would be fine.
 
I have a Rosemount pressure transmitter (using for level) that is connected to a Allen Bradley Micrologix PLC analog card. To communicate with a 475 does the resistor need to be in series or parallel? I also cannot get the analog to read at the PLC, do I need to put a 250ohm resistor in series with the 24VDC+?
 
HART needs a minimum of 230 ohms in the loop. An analog input (AI) supplies some resistance, but the value varies from manufacturer to manufacturer. If that A-B AI uses, say 100 ohms, then you need more resistance in series in the loop, but not across the (+)/(-) of the AI.

There's a multitude of reasons why you might not be able to read an AI value: wiring, configuration, scaling, logic.

You need to separate reading HART with a 475 issue from reading the value on an analog input issue.

Putting 250 ohms in the loop will (probably) not help you read the analog value at the input, it might help the 475 to read the HART data.
 
Hi to every one.....

Thanks in advance for ur reply.....

I am facing the same problem with my 3051 rosemount PT. The tx. is powered from siemens PLC AI card. if i connect HART it shows NO DEVICE FOUND. When i connect a 24V DC source it communicates properly.

As per the earlier post, does it mean that the 24V source has sufficient loop impedance which is not present in field wiring (tx. to PLC's AI card)? Then, whats the proper way to measure the loop impedance in both cases (through source & through field wiring).
 
Four things are needed for HART communication:

1) a HART enabled transmitter
2) a DC power supply
3) a minimum of 230 ohms of resistance
4) HART communicator (with good batteries) or a HART modem/PC/software

If this is done on a bench, then the resistance needs to be a physical resistor.

If this is done in the field, then the resistance is usually supplied by the analog input. But as others, like Roy, have pointed out, sometimes analog input resistors are less than the required 230 ohms so a resistor needs to be added to the loop to increase the loop resistance. The old 275 had a resistor on banana plug adapter that would provide loop resistance.

When you say, 'if I connect HART it shows ____", do you have all the required components?

The DC power supply does NOT have sufficient impedance, in fact, it is a low pass filter that eats the HART signal.
 
J
Does the transmitter power "on"? Does it have an LCD which is lit? Is the
current in the loop > 4 mA? What is the voltage on the transmitter
terminals?

Depending on the system, you must wire the transmitter differently depending on if it is loop powered (two-wire) or separately powered (four-wire). If card is wired incorrectly the transmitter will not power on.

For other systems you may need to configure the AI card to operate as two-wire or four-wire. If the card is configured incorrectly, it will not power the transmitter.

Cheers,
Jonas
 
I had the same issue with a level transmitter of ours, but was eventually able to solve it like this:

On the Hart Application Menu (says Offline, Online, Utility, etc)
-Select 'Utility'
-Select 'Configure HART Application'
-Make sure 'Poll by Address' is selected under 'Polling Options'
-Change 'Polling Addresses' to 0-15

Most transmitters have polling addresses of 0, but some have higher addresses, so they won't be found unless the communicator is looking for higher addresses.

This did the trick for me!
 
I had the same issue with a level transmitter of ours, but was eventually able to solve it like this:

On the Hart Application Menu (says Offline, Online, Utility, etc)
-Select 'Utility'
-Select 'Configure HART Application'
-Make sure 'Poll by Address' is selected under 'Polling Options'
-Change 'Polling Addresses' to 0-15

Most transmitters have polling addresses of 0, but some have higher addresses, so they won't be found unless the communicator is looking for higher addresses.

This did the trick for me!
So, I have a brand new out of the box Fisher DVC 6200 positioner on a Fisher valve being powered by 24VDC Delta V 4-20mA loop (AO).

Connected a new Emerson AMS TREX to configure device. "NO DEVICE FOUND", "NO VOLTAGE FOUND". Check voltage with FLUKE 789, reading 6.3VDC.

I've come across this issue with the 6000 series positioners many times and have fixed it by simply cycling power, and 99.999% of the time, it fixes the glitch.

HOWEVER, it didn't fix this. Disconnected field wire from DVC, 23VDC with 789. Terminated wires to DVC, 6.3VDC with 789 and no comms with TREX, nor 475.

To make sure it wasn't the DVC, I grabbed another brand new in box DVC off the shelf and powered it up at valve. SAME THING! "NO POWER DETECTED", "NO DEVICE DETECTED" on TREX and 475, 6.3VDC with 789.

Disconnected Delta V loop power, powered DVC using TREX power, NO PROBLEMS. 100% comms with DVC<->TREX. Stroked valve with TREX and FLUKE 789. DVC GOOD.

Configured DVC with valve & actuator specs via TREX power, checked for alarms and faults, NONE. Reconnected Delta V loop power, "NO DEVICE FOUND" with TREX, 475, or DCS.
SHIT!! Gotta be a bad wire or Delta V Card.

Disconnected wires at DVC, AJB, Marshalling rack, and fuse block in in controller cabinet. Ohmed + to shield, "OL", - to shield, "OL", + to -, "OL" (end to end on each segment). Left DVC end disconnected, reconnected both sides in AJB with Marshalling disconnected, "OL" on all ckts. Homerun from marshalling to DVC is GOOD.

Reconnect at marshalling, check resistance at DVC (wires disconnected), + to - = 25M, + to ground = OL, - to ground = 92K.

Ohmed Delta V card + to - = 25M, + to ground = OL, - to ground = 92K.

Same card, one channel up, same exact Fisher valve with same exact DVC, in service, working fine. No errors on card in AMS, or flashing on card.

DVC, homerun, terminations, Delta v card & channel = ALL GOOD.

WTF???
 
As I read your assessment, it appears that the DVC works independently (outside of) the bad-boy loop, right?
I'm not sure what your 6.3Vdc reading is, or why the - to ground Ohms-out at 92K ohms, but you seem to be OK with that.

So what non-run-of-the-mill thing is going on?

I/S barrier?
I am unaware of I/S barriers causing a problem except for failing (opening their fuse) due to performing their safety function, but your cabling checks don't mention an I/S barrier.

DC power supply?

Noisy power supplies are known to fault HART even though the 4-20mA signal is OK. Would a Delta V AO card do anything other than parallel the system DC power to each I/O point? Even if each channel is fused internally, the loss of a fuse would not provide any voltage. Where would the noise for one channel come from that is absent from other AO channels on the same card? I have run into linear power supplies that lost a a diode in the rectifier and couldn't produce the rated voltage under load; the voltage would appear OK with no load but as soon as a load is applied the voltage dropped below the minimum required. Again, I assume the Delta V AO card uses either system/rack power or DC power supplied to a common pair of terminals, which means all channels presumably get the same DC power. If the card is supplied from exterior DC supply, could the DC supply be maxing out with the added load of another channel?

Too many HART masters?
HART has a limit on masters, I'll call them a primary and a secondary master. AMS is the primary master, the TREX or 475 can operate as a secondary master. Adding a 3rd master is a problem. Has a 475 been left connected and enabled which is hogging the secondary master rank?

Load resistance too high for an active AO?
Is the load exceptionally high because of seriesed loads? You haven't mentioned it so I doubt it, but I have seen where an AO DC power supply can’t drive the loop current through the loop resistance. I had to use an AO splitter module for a split range app; AO could not drive two I/P’s or two positioners in series. Is there another loop indicator of load somewhere else in the loop?

HART signal-eater device?
There are 4-20mA accessory devices that are not rated for HART pass-through because their input circuits have low pass filters that filter out the HART signal (or a technology that doesn't recognize HART, like optical isolation); devices like digital indicators, isolators, splitters. Is there a low pass filtered HART signal-eater in the loop?
 
So, I have a brand new out of the box Fisher DVC 6200 positioner on a Fisher valve being powered by 24VDC Delta V 4-20mA loop (AO).

Connected a new Emerson AMS TREX to configure device. "NO DEVICE FOUND", "NO VOLTAGE FOUND". Check voltage with FLUKE 789, reading 6.3VDC.

I've come across this issue with the 6000 series positioners many times and have fixed it by simply cycling power, and 99.999% of the time, it fixes the glitch.

HOWEVER, it didn't fix this. Disconnected field wire from DVC, 23VDC with 789. Terminated wires to DVC, 6.3VDC with 789 and no comms with TREX, nor 475.

To make sure it wasn't the DVC, I grabbed another brand new in box DVC off the shelf and powered it up at valve. SAME THING! "NO POWER DETECTED", "NO DEVICE DETECTED" on TREX and 475, 6.3VDC with 789.

Disconnected Delta V loop power, powered DVC using TREX power, NO PROBLEMS. 100% comms with DVC<->TREX. Stroked valve with TREX and FLUKE 789. DVC GOOD.

Configured DVC with valve & actuator specs via TREX power, checked for alarms and faults, NONE. Reconnected Delta V loop power, "NO DEVICE FOUND" with TREX, 475, or DCS.
SHIT!! Gotta be a bad wire or Delta V Card.

Disconnected wires at DVC, AJB, Marshalling rack, and fuse block in in controller cabinet. Ohmed + to shield, "OL", - to shield, "OL", + to -, "OL" (end to end on each segment). Left DVC end disconnected, reconnected both sides in AJB with Marshalling disconnected, "OL" on all ckts. Homerun from marshalling to DVC is GOOD.

Reconnect at marshalling, check resistance at DVC (wires disconnected), + to - = 25M, + to ground = OL, - to ground = 92K.

Ohmed Delta V card + to - = 25M, + to ground = OL, - to ground = 92K.

Same card, one channel up, same exact Fisher valve with same exact DVC, in service, working fine. No errors on card in AMS, or flashing on card.

DVC, homerun, terminations, Delta v card & channel = ALL GOOD.

WTF???
6.3Vdc is too low for DVC to work...Your voltage drop is too much...minimum voltage required would be around 10Vdc at 20mA if I may remember it correctly.
 
Udshread recalls the minimum spec properly - 10Vdc at the terminals, as confirmed by the Rosemount DVC6200 spec sheet:

https://www.emerson.com/documents/a...VC6200-Digital-Valve-Controller-en-123336.pdf

View attachment 2237
Hi David_2
Actually it is the same for other smart positioners like Sipart ps2, Ebro Ep200 etc.When I was working in core instrumentation maintenance & projects, I always kept this value as a rule of thumb during troubleshooting & commissioning. Infact it is actually for almost all smart positioners out there in the market. Guys like Siemens and Ebro they mention it in loop resistance which when converted to voltage gives around 10VDC.
 
Hi, I have a newbie question.
I've got this AMS Trex supplied by our company and I tried to explore it.
I have a rosemount Pressure transmitter with Hart function in it, and use it as my test subject.
I followed the connection shown in the manual (I used externally powered) and connect accordingly.
Then I am getting a Voltage detected and Hart detected status then navigating me in a screen where it says "no device connected".
Is there anything that I missed that I must do first?
I'm really interested to learn it how, hope someone could help me out there.
 
Trex has either 250 or 500 Ohm resistors internally that it can use in its HART sense circuit. Somewhere in the menu you get to pick.

At $12K+, I don't have aTREX laying around to experiment with. Read the manual to find out how you navigate the menu to get enough loop resistance to get a valid HART signal.
 
I just follow what the manual says. I used an external powered set up where the negative supply has to have a 250ohms in series to the transmitter, and the trex' probes are connected in parallel with the transmitter. The manual's illustration is pretty straightforward. Even trex confirmed the hart was detected and voltage in the transmitter. Even the tagging was identified, however, once I connect, it says cannot find the device. I will attach some photos here.
 

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