Frequently Asked Questions

1. Why should I choose SMART over Analog?
2. Why would I choose Analog over Smart?
3. What is HART?
4. What is a HART-to-Analog Signal Converter?
5. Why is my Model 275 or 268 HART Communicator not communicating?
6. Why can't I configure my Model 3144D with my 268 or 275? I cannot change the sensor input.
7. With so many instrument manufacturers providing HART devices, how can I be sure that the HART Communicator I buy today will speak to the transmitter I buy tomorrow?
8. If I have a unit that fails, or I need a spare unit in a hurry, where do I get help?
9. What is the Mean Time Between Failures for our Transmitters?
10. I want to measure Bi-directional flow with your magmeters. Will they measure reverse flow?
11. What startup procedure is required with the Model 8800 Vortex flowmeter?
12. Can the Model 8800 pulse output be wired with only 3-wires?
13. How does Hydrogen Permeation commence and what are the effects?
14. Where is the Model 1151LT information in the new hardbound Comprehensive Catalog?
15. Why does it cost more to get a transmitter from a service center than from the factory?

1. Why should I choose SMART over Analog?

Smart transmitters can offer improved and safer plant operation through remote communications capabilities.

• Greater transmitter accessibility in difficult access locations
• Increased personnel safety in potentially hazardous locations
• Easier plant check-out and faster start-up/commissioning

Smart transmitters can offer improved maintenance capabilities through diagnostics.

• Simplifies transmitter and loop verification
• Identifies the failure mode
• Eases troubleshooting/diagnostics from control room

Smart transmitters offer more functionality

• Linear/square root selection
• Transmitter security
• Alarm selection capability

Smart transmitters can offer improved performance

• Increased stability of digital electronics
• Increased transmitter accuracy
• Additional temperature compensation (Phase II electronics are characterized over temperature.

2. Why would I choose Analog over SMART?

For certain applications and models, analog electronics may offer a faster response than smart electronics for applications where time response is critical. 

In applications that require nuclear containment (such as nuclear power plants), certain regulatory bodies do not allow the use of microprocessors, which can be affected by radiation. 

3. What is HART?

H.A.R.T. stands for Highway Addressable Remote Transducer.

This is a communications protocol that allows transmitters and other equipment to communicate with control systems, valves, etc...

It works very much like two computer modems communicating over a phone line. One device sends a command and the other responds. This continues back and forth between the two systems. The devices automatically check for errors in the received data to prevent interference.

HART is a open (non-proprietary) standard that currently has over 1.5 million installations and growing daily.

Check out The Virtual HART Book for more information on HART.

4. What is a HART Tri-Loop HART-to-Analog Signal Converter?

Rosemount manufactures a device called the HART Tri-Loop^TM HART-to-Analog Signal Converter.

This device will take the HART output from our Model 3095 flow transmitter and "split" it into three separate 4–20 mA signals. With this device, the user can take one 3095 MV^TM Multivariable^TM Mass Flow Transmitter and effectively put it to work as four transmitters outputting flow, temperature, differential pressure, and absolute pressure. The Tri-Loop Converter can also be used with the Model 3244 Smart Temperature Transmitter to output T1, T2, and delta T.

5. Why is my Model 275 or 268 HART Communicator not communicating?

There are several possible reasons why a transmitter might not respond to a communicator but the most likely is that the user doesn't have the minimum 250 ohms of loop resistance.

6. Why can't I configure my Model 3144D with my 268 or 275? I cannot change the sensor input.

Hand held communicators have specific commands trees for various instruments.

If the command tree for the 3144D is not programmed into the 275, only a generic tree will be available. To find out which instruments your hand held is mapped for, select Off-Line, select add new instruments. A list of current instruments programmed for the hand-held will then be displayed.

7. With so many instrument manufacturers providing HART devices, how can I be sure that the HART Communicator I buy today will speak to the transmitter I buy tomorrow?

Rosemount is aware that there are many different HART Devices coming into the market on a daily basis.

We now offer a 2 year service agreement as an option with our 275 communicator. The Basic option will give the user 5 upgrades, while the Premium option will give the user unlimited upgrades over the 2 year period. So long as the manufacturer of the HART Device has registered it with the HART Foundation, the device descriptors can be added to our 275 communicator.

8. If I have a unit that fails, or I need a spare unit in a hurry, where do I get help?

In the United States, during regular business hours, call Rosemount Customer Central at 1 (800) 999-9307.

We have highly-trained technical and administrative support staff available 12 hours a day (M-F) from 7am - 7 pm CST. If assistance is needed during weekends and after hours, our North American Response Center at 1 (800) 654 7768 can take care of getting the assistance that you need. For the location of the nearest customer service center in other world areas, please contact the sales office nearest you. (See World Contacts.)

9. What is the Mean Time Between Failures (MTBF) for our Transmitters? 

MTBF data changes regularly as more units are tested.  The following data is from the quarter ending September 30, 2003. 

10. I want to measure Bi-directional flow with your magmeters. Will they measure reverse flow?

Yes!

Our magmeters will measure reverse flow by activating "reverse flow enable" in the 8712C. The 4–20 mA output will be identical for both forward and reverse flow.

11. What startup procedure is required with the Model 8800 Vortex flowmeter?

Before startup, it is necessary to configure the Model 8800 for the specific application on which the meter is installed.

If a configuration data sheet (required on every order) was completed, the factory will have configured the meter with the values provided on the configuration data sheet. Otherwise the flowmeter is given a standard factory configuration, which needs to be changed to fit the specific application.

To configure the flowmeter for an application, use the Model 268 or 275 HART communicator and enter the CONFIGURE/CHANGE OUTPUT section of the software. Step through the various parameters in this section to make sure the values are all consistent with the application and change any values that are not.

[Note: The service type (gas or liquid) is the most important parameter to check, followed by flow unit selection.]

12. Can the Model 8800 pulse output be wired with only 3-wires?

Yes, a 3-wire installation is possible.

The only limitation of a 3-wire installation, as opposed to the standard 4-wire hookup, is that the HART signal is not available due to increased noise in the wire.

To Wire the Model 8800 pulse output using a 3-wire hookup, follow these wiring instructions:

1. Install a jumper wire on the Model 8800 between the negative 4–20 mA terminal and the negative pulse terminal.
2. Install a 1 K-ohm resistor on the Model 8800 between the positive 4–20 mA terminal and the positive pulse terminal.

13. How does Hydrogen Permeation commence and what are the effects?

Monatomic hydrogen can be formed in a process fluid that has conductivity, when components of the piping system consist of dissimilar metals.

If the voltage difference of those dissimilar metals is large enough, hydrogen will be generated and will then diffuse through the diaphragm as H+ and recombine on the backside of the diaphragm as H2 molecular hydrogen. The effect is seen as drift in the output, and eventually the diaphragm will "jiffy pop" due to increased pressure. Hydrogen permeation can be avoided by minimizing the use of dissimilar metals in the system.

14. Where is the Model 1151LT information in the new hardbound Comprehensive Catalog?

In the 1199 section only. It is not listed in the index so it is difficult to find.

15. Why does it cost more to get a transmitter from a service center than from the factory?

Cost!

A factory is much more efficient and can produce the same item at a much lower cost, but with slower response time. The service centers can respond faster, but at a much higher cost. So the additional cost is reflected in the order that generates the cost, not spread over all of our transmitter orders.

Emerson Process Management, Rosemount Division, 8200 Market Blvd. Chanhassen, MN USA 55317 North America: 1-800-999-9307    International: 952-906-8888  Fax:  952-949-7001