level measurement

Manual? I don't need no stinking manual!!!! Well... actually you do.

Ignoring Installation & Operation Manuals can lead to frustration and many times extra cost for users, installers and even manufacturers supplying the equipment being installed.  This is something we in Tech Support face almost daily.  All too frequently people installing level sensors do not consult the Installation and Operation Manual beyond where to connect the wires carrying the supply voltage and to identify where to connect the wires for the output. Then, when the sensor does not work or it fails shortly after installation, they call and ask for help often blaming the manufacturer for a poor design (sigh). For point level devices that are fairly low-tech this usually does not present a problem but here are a few real examples of issues we have faced where the installer or customer did not adequately prepare for the installation by reviewing the Installation & Operation manual provided with the level sensor.

1. An RF Capacitance probe mounted was mounted directly in the fill stream of a very abrasive material.  Result?  The insulator between the active probe section and the driven shield (used for build-up immunity) was literally blasted away.  This rendered the probe useless. Solution?  Install a baffle inside the vessel to eliminate direct impact of the fill stream as recommended in the Installation & Operation (I&O) manual provided with the sensor.
2. A guided wave radar continuous level measurement sensor "locked up" at a fixed distance from the mounting flange.  This measurement did not reflect the correct material level. Cause?  It was discovered that the vesel being measured had horizontal I-Beam supports a mere three inches away from the probe.  This close proximity caused enough signal reflection to fool the sensor into thinking it was the actual material level reflection pulse. Solution?  Relocate the sensor to provide the minimum probe clearance as stated in the I&O manual.
3. A Smart RS-485 inventory monitoring installation with 10 sensors that were connected to a PC running Inventory Management Software.  The sensors would not communicate with the PC. The software indicated a communication error for each sensor on the network. Cause of problem?  The installer ran a sepparate RS-485 cable from each individual sensor back to the PC and tied all the wires together in a junction box. This caused so much noise on the network that the PC could not read the digital signals. Solution?  Rewire the sensors in a "Daisy-chain" fashion as described in the I&O manual. In this case, the installer thought that RS-485 was to be wired just like analog devices would be and reading the I&O before performing the actual installation would have saved him.

The list goes on.  But, as technology evolves, installers need to drop their "old school" ways and read the Installation manuals before they perform the actual installation. If an existing process connection does not meet the minimum installation requirements, they are asking for trouble by not installing a new process connection that does. A botched installation takes time and costs additional time and money to correct.  It creates conflict among people and can in some cases result in hard feelings between all involved parties.  That is not good.

One way to help avoid all this is for you or your installer to contact the manufacturer's Technical Support Department to review and discuss the proposed installation in detail. The engineer at the factory will know what questions to ask the installer to be sure the installer knows how to correctly install and commission the system.

Greg DeRudder

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Using flexible extensions with bin level sensors

Using extensions on level sensors that are used to monitor high level conditions in bins and silos is not new.  Many applications exist where the shaft is extended up to 12' from the mounting point of the level sensor.  These situations are when the senbsor is mounted on the top of the vessel, not the side.  However, sometimes the length of the extension, the type of material and its flow characteristics are such that the side loading caused by material flow and movement can be damaging to the sensor.  In these situations a "flexible" cable extension is desired to be used.  We recommend these flexaible extensions for use with rotary paddle type bin level sensors up to several feet, however, we are aware of customers using longer lengths.  The real limit on the length has to do with actuation time due to the rotation of the sensor output shaft and the twisting of the cable.  Up to six or so feet will provide reliable actuation of the sensor.

Next time you need an extensions for your rotary paddle bin level sensor for high level control consider a flexible extension.  The length is even easily modified in the field.

Joe Lewis

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Dust can be a problem when adding Computer Hardware

Recently I flew to San Antonio to resolve an issue where an RS-485 Flexar unit absolutely would not communicate with a recently installed RS-485 PCI Bus adapter.  In this case, the computer recognized the card and drivers to be installed correctly because there were no errors reported when the hardware was examined in Control Panel of a PC running XP-Pro Service Pack 2.

After climbing the silo, examining all the wiring and soldered connections, verifying the sensor was functional at the process connection, I was ready to pull my hair out (It's OK, I have a lot for a man of my age).  I had taken my laptop and a USB RS-485 converter with me.  As soon as I plugged the customer's communicaion cable into my computer equipment, I had instant and reliable communications established. 

Since the above actions isolated the problem to the customer's PC, we took the covers off and moved the PC to a different slot. In doing so, I could feel the grit on the electronic connections as I pulled the board out. To make a long story short, I took a deep breath and blew what I could out of the PCI Bus connector on the pc, re-installed the RS-485 adapter, and upon power up established a successfull communication link between sensor and PC. Obviously, dust and dirt can be a good electrical insulator.

So, if you ever install computer hardware in a PC that has resided in a dusty/dirty environment for some time, I would consider taking the CPU outside and blowing it out with compressed air before performing the hardware installation. So, Concrete batch plants - take notice. :)

As a side note, there are industrial grade PC's on the market that are well sealed and cooling air is well filtered. They cost typically 4 to 5 times more then a generic pc at your local super store but may indeed be worth the price to you.  However, filters require periodic maintenance. Food for thought.

Greg DeRudder

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Getting the Most out of that Expensive Service Visit.

Having a factory technician visit your facility for non-warranty service can be expensive.  After years of conducting field service visits, here are a few few tips I'd like to offer to help get the most from this expensive eventuality.  Yes, some of these tips may seem obvious but sometimes these things just have to be mentioned.

A)  Provide a listing of the equipment to be serviced.  OK, this tells us what parts may be needed - or if the equipment is even serviceable.  Providing no information leads to assumptions, the results which can be unpleasant.

B)  Provide a description of the problem experienced.  It'd be a shame to spend mucho molla only to hear that the problem is not a result of, or directly related to, the suspected piece of equipment being serviced.

C) Show up for work the day of the scheduled service visit.  No joke, it happens all too often that I have traveled to a job site to service a piece of equipment only to find that my site contact has taken the day off. The service activity will proceed but it's now up to the service tech to define the problem.

D)  Assign a responsible person to work with the technician.  Sort of related to item C above.  This facilitates communication and insures that the servicing proceeds at an efficient pace.  Often is is necessary for the tech to access other equipment and a company agent can provide direction and help mitigate any process disruptions.  Additionally, training/guidance as to the routine or periodic maintenance issues can be transfered which just might eliminate the need for future visits.

E)  Be available for a review-of-service briefing.  Hey, a bunch of money was just spent - don't you want to know how and why?  Also, a review of the work completed can insure the original problem was indeed remedied.

Andy Bowman

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