Selecting a Transmitter


Thread Starter


In case of Pressure, temperature, level etc. process instrumentation vendor selection, if all the vendors meet basic requirements according ISA standard form, then how could i select the best one? In other words, how could i trust a new vendor for instrumentation as i never used his product before?
Some thoughts

Commodity items can be purchased based on quotes for price, availability, and delivery times because they're commodities: six of one, half dozen of another. If what you're buying is not a commodity item, you're not really buying the 'thing'. You're entering into a relationship with a vendor, as scary as that might be.

The reputation of the vendor (manufacturer and rep/distributor) helps in your decision process. The major vendors didn't get to a major position by selling stuff that does not work, although every vendor has had a lemon now and then. The major vendors tend to have high performing reps/distributors. Established products from major vendors tend to be quality products. That said, major vendors can fall behind because their internal bureaucracies fear risk and innovation. Sometimes the non-majors do have the better product. And in some cases their service is better because they're more hungry for the business.

Recent buy-outs warrant extreme caution. The people from the bought-out company who had the experience and knowledge are frequently down-sized for purposes of "synergy".

It sometimes pays to talk a salesman. Some salesmen are worthless toads, others have vast experience and have seen lots of apps. They can bring some value to the decision process by bringing up alternatives that you haven't considered. Set the agenda, establish a time limit up front and get down to business. Ask, "What haven't I considered? Why buy yours? What do you bring to party? What happens if it's a lemon? If my guys need training, how does that happen?"

Let me give an example. A salesman asked who would be using a device. It probably would be a Spanish speaking Mexican. Would it help to have prompts in Spanish? You bet it would. Not all devices had a Spanish language option.

Take a look for yourself at the vendor's web site. Can you find the spec/data sheet for your product? Can you find the installation guide and operating manual? Can you find a communications manual? Are there app notes and white papers for various applications? App notes demonstrate an expertise. Don't expect to find pricing (it's not a commodity), but do expect to find what you need to install and operate the thing and hopefully info on helping you make a decision (like an app note). If stuff isn't on the web site, what's that tell you?

2) Have you read the manual? Could you install, maintain and calibrate it with the information provided? Is it illustrated (picture worth 1,000 words). I ran into one the other day that had NO troubleshooting section. None. Does the manual you're looking at have a troubleshooting section? Parts list? Illustration or just lots and lots of words in a foreign language?

3) Other Resources
A major vendor uses the term "Output bias" as a smart valve positioner error code, but do not explain what output bias is in the manual. What are the resources available when the manual just doesn't have the info needed?

Does the vendor have YouTube videos showing setup or calibration or troubleshooting? (Most have exciting sales videos, which are rarely of any help for anything).

4) What do others say?
Most internet fora limit content so that posts are not outright sales pitches. But you will find comments on occasion about a vendor who hasn't replied in three days to a request for help and that's why the poster came to the forum.

I'm surprised at how infrequently vendors actively participate in internet fora. There's a couple protocol converter vendors that are regulars here on And there's an HMI vendor who regularly participates on a PLC forum (the company president answered once) and has gotten lots of conversions to their brand because forum regulars know that they can get qualified help quickly that way. But I don't see a lot of vendor participation beyond that on public fora. In fact, many vendor-specific questions (particularly on level radar, I notice) go unanswered forever. It's the great mystery out there.

Bob Peterson

Some transmitters are pretty much commodity items. No reason not to buy them with an eye toward costs savings. I would say most pressure and temperature transmitters fall into this category, short of some exotic materials requirement.

Sometimes you need help from the supplier on an ongoing basis and you probably want to select a supplier more carefully in that case.

You will probably find that there is very little performance difference between common pressure and temperature transmitters from the well known and even lesser well known suppliers. They are a well understood measurements and it is not as if there is likely to be anything new and exciting happening.

However, it may turn out that a D/P application (say with remote seals) might require a little more thought and help from the supplier.
That's a good point Bob made, that one needs to consider, help from the supplier. When you buy on price only, you may be giving up the opportunity to have special services such as a customized solution, and you may be giving up after purchase support.

Choose a vendor based on years in the business, reputation, range of products offered, warranty, standards that they support and follow, and local support.

The modern smart HART transmitters as offered by the main manufacturers such as Emerson Rosemount, E&H, Yokogawa, etc are a bargain. A loop powered smart pressure or radar level transmitter certified for IS, explosion proof and general purpose NEMA 4 for $1.5-2K.

We had old Bailey analogue pressure transmitters in our powerhouse that lasted 30+ years. The new smart digital transmitters are better, more robust, reliable, repeatable, accurate and vibration resistant.

good luck
The other important thing to check such as branch office/local agent, after sales service, spare part availability, special tools (if required, like HART Communicator etc), warranty period & delivery time (if we order).

Technically we shall check by read the manual about how to calibrate and configure (HART support or use the other protocol) transmitter itself.


Thank you David, now i am pretty much clear. And on more point how much it would be helpful to visit manufacturing site?

Thanks again
In my opinion, it's not worth it to visit the manufacturer (and I've done it).

In today's global manufacturing environment, which manufacturing site is the critical one? The vendor casting the housing and their quality control (or lack of it) in chasing the threads for conduit fittings or the cable assembly plant or the sensor plant or the injection molding plant where the terminal blocks are made, or the the final assembly plant where the screwed together and the name plate riveted on? Or the chemical plant that manufactures the epoxy coating on the housing?

My view is that one has to assume that the manufacturing does its job.

The big question is, what happens when there's a problem (which might not be manufacturing; it could be design or a single bad component)?

I don't rate vendors and their products on whether or not they have a problem, it's how they take steps to fix whatever the problem is, whether that's delivery, some technical issue or lack of documentation. I have not encountered those kinds of responses in plant tours.