Monday, November 13, 2006

Unique Sensor Solution for Use in Vehicles

originally posted by littlec

HELSINKI, FINLAND — (MARKET WIRE) — October 12, 2006 — VTI Technologies, the major manufacturer of high-performance motion and pressure sensors for automotive and consumer related applications, is launching a best-in-class accelerometer and inclinometer platform for vehicle stability control and related systems worldwide.

The new VTI automotive digital accelerometer platform is intended for single and multiple axis acceleration and inclination measurement. It has been developed to meet the most demanding needs of vehicle electronic systems using digital signal processing, introducing several important safety features such as continuous self-test. The components form a complete set of low-g accelerometers with the same mechanical design and SPI-interface. They are small in size, high in performance and require only one PCB design for all versions. They cover acceleration and inclination measurements in applications like Electronic Stability Control (ESC), Hill Start Assistant (HSA), Electronic Parking Brake (EPB), Roll Stability, Roll Over and Electrically Controlled Suspension. The multiple options for each car platform can be covered with one ECU or sensor cluster design by selecting the appropriate sensor version from VTI’s new accelerometer Series.

“This new digital concept offers acceleration and inclination sensing as a complete platform, which has in all directions the same pin-out in one-, two- and three-axis accelerometers. This means major savings to our customers in broad range of automotive applications”, explains Hannu Laatikainen, Vice President of Sales and Marketing for automotive products at VTI. “The new generation of 3D-MEMS sensing elements for multiple axis are very small (2.6 x 2.0 x 1.6 mm), allowing same package size for all designs from one to three axis. These products also support the trend in automotive electronics towards smart integration and better reliability with intelligent self-test features — more intelligence and functions included into the same sensor packages.”

A major application area for the new accelerometers is in the sensor cluster needed for ESC. ESC is an active safety system that recognizes unstable driving conditions at the very outset and applies corrective action automatically. ESC works by monitoring the actual car motion with several sensors and compares this information to the driver’s input. In an unstable condition, the ESC intervenes via the engine electronics and the brake system to help stabilize the vehicle. An accelerometer is needed as part of ESC to measure lateral acceleration. In more advanced vehicles and systems, longitudinal acceleration/inclination is measured if the car is 4-wheel driven or has an automatic Hill Start Assistant function or Electronic Parking Brake. Vertical acceleration measurement is needed for suspension and roll over detection.

Monday, November 06, 2006

MIL-STD (Military Standard) or MIL-SPEC (Military Specification)

The MIL-STD specification is a series of guidelines established by the U.S. Department of Defense in order to define specific performance and manufacturing requirements for all types of equipment.

In most cases, products must be designed in accordance with the MIL-STD to be considered acceptable for use by the U.S. Department of Defense. A product's MIL-STD compliance is also a consideration for many state and local governments when purchasing mobile computers for use in public safety, emergency services, maintenance, etc.

The MIL-STD 810F standard was released on January 1, 2000 (superseded MIL-STD 810E). MIL STD 810F includes testing protocols to simulate environmental stresses from rain, humidity, salt fog, sand/dust, vibration, shock, temperature, etc. A copy of MIL-STD 810F can be downloaded from the United States Army Developmental Test Command.

The MIL-STD 810F standard is an all-encompassing standard that is frequently used for ruggedization testing by mobile computer manufacturers. Many manufacturers and laboratories will design their ruggedization testing in accordance to the MIL-STD 810F guidelines. However, it is important to note that when the MIL-STD 810(x) specification is listed on a product's data sheet, this usually only applies to the vibration and shock component of the standard, and does not mean that protection is included from salt fog, corrosion, rain, humidity, temperature, etc. Therefore, IP or NEMA Ratings are frequently used to signify protection from liquids and solids, and the MIL-STD is used to specify protection from shock and vibration.

Friday, November 03, 2006

Back Lit Boom Angle Indicator - Meets NFPA 1901 Standards for Automotive Fire Apparatus

This upgraded 4120 boom angle inclinometer provides the end-user the best functioning unit available.

First and foremost, the new revision addresses durability. Made of 100% Polycarbonate material with a unique and patent pending technology, it is extremely durable, shock and vibration resistant. Our main objective was to help avoid accidental breakage during installation or the rough environment off road forklifts are typically used. As an added benefit of the new durability we will ship more product in smaller containers with less packing material. This will decrease the cost of shipping.



The second feature to our new product is the option for backlighting. This is the reason the color has changed to white with black markings. This subtle change has allowed us to provide a weatherproof lighting feature making it highly visible at night. Backlighting is available in either AC or DC for the following voltages; 24V, and 12V (rated for 20,000 hours).

Meets NFPA 1901 Standards for Automotive Fire Apparatus


First of its kind design allowing the angle to be read from below, above and the side. Oversize markings for easy read up to 30 ft away. These instruments are made tough and will not rust, freeze, or otherwise "hang up" like old-fashioned pendulum styles - not effected by outdoor elements. Like all of our manual instruments, each indicator is properly dampened for smooth reliable readings. The 4120 model is designed for easy mounting with two screws, which allows for quick and efficient retrofitting in the field. The newest addition is the 4120-12v, a highly visible backlit model for increased safety - especially at night!

Thursday, November 02, 2006

Environmental Protection Part 2: NEMA Ratings

NEMA (National Electrical Manufacturer Association)

NEMA ratings are standards that are useful in defining the types of environments in which an electrical enclosure can be used. The NEMA rating system is defined by the National Electrical Manufacturer Association, and frequently signifies a fixed enclosure's ability to withstand certain environmental conditions. Please refer to the table below for specific NEMA type designations.

NEMA ratings are rarely applied to mobile devices, and are mainly applied to fixed enclosures. For example, a NEMA rating would be applied to a fixed electrical box mounted outside, or a fixed enclosure used to house a wireless access point. Most enclosures rated for use in an outside environment include a NEMA 4 rating. NEMA ratings have more stringent testing requirements to verify protection from external ice, corrosive materials, oil immersion, dust, water, etc. These stringent testing requirements can rarely be applied to mobile devices, but there is a correlation between NEMA ratings and IP ratings. However, this correlation is limited to dust and water. The "Comparison Table" below provides a comparison between NEMA ratings and IP ratings. It is important to realize that this comparison is only related to the protection provided against dust and moisture. For this reason, this table can only be used to convert NEMA ratings to IP ratings, but not vice versa. A few manufacturers of mobile computers will include NEMA ratings in their specifications, and it is important to understand how the NEMA specification correlates to a product's IP Rating.

Wednesday, November 01, 2006

Environmental Protection: IP Ratings and Rugged Inclinometers

Environmental Protection When Considering an Inclinometer for Your Application.

A truly rugged industrial device is engineered, from the ground up, to operate in the most extreme hostile environments. The industrial engineering design is not only limited to the external housing, but includes internal components, special coatings, sealants, and other design features allowing computers to be exposed to extreme humidity, dust, temperatures, vibration and shock. Included in the mix is a class of products manufactured explicitly for use in hazardous or explosive environments.

IP Ratings
IP (Ingress Protection) ratings are standards for electrical enclosures. The rating refers to the equipment's ability to permit solids and liquids to penetrate the computer's enclosure. The protection standards are defined by the IEC (International Electrotechnical Commission). A mobile computer's IP Rating is expressed as a two-digit number (Example: IP-66). The first number designates protection from solids, while the second number designates protection from liquids. Please refer to the table for specific IP rating information.

Tuesday, October 31, 2006

Cross-axis Sensitivity Relating to Liquid Capacitive Inclinometers

Cross-axis sensitivity or "angle orthogonal to the plane of measurement":

Cross axis sensitivity is a proportionality constant that relates the change of the inclinometer output induced by a cross acceleration/inclination input. The sensitivity can vary depending on the direction of the cross input.

For example: A liquid capacitive gravity based sensor needs to be mounted in a vertical position - if the back of the inclinometer is mounted 45° off of vertical one would expect the inclinometer to be accurate within 0.1° of the expected output when mounted vertical. Due to the unique cavity design the error is predictable without much overall change to the accuracy. The unit will still provide output along the sensor's degree range, however the error at larger cross angle inputs will be significantly higher - as much as 2 or 3 degrees - the further off vertical the sensor is mounted.

It is recommended to mount a gravity based inclinometer sensor as close to vertical as possible to maintain the integrity of the sensor's output.

Monday, October 30, 2006

What does it mean to be Intrinsically Safe?



INTRINSICALLY SAFE INCLINOMETER PACKAGES (SINGLE OR DUAL AXIS, 4-20mA output)


What does it mean to be Intrinsically Safe?

The term "intrinsically safe" refers to equipment and wiring which is incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture in its most easily ignited concentration. This is achieved by limiting the amount of power available to the electrical equipment in the hazardous area to a level below that which will ignite the gases present. To be certified "intrinsically safe," a device or circuit must be so designed that no two simultaneous failures can cause an explosion.


In order to have a fire or explosion, fuel, oxygen and a source of ignition must be present. An intrinsically safe system assumes that fuel and oxygen are present in the atmosphere, but the system is designed such that the electrical energy or thermal energy of a particular instrument loop can never be great enough to cause ignition. Traditionally, protection from an explosion in hazardous environments has been accomplished either through the use of explosion proof conduits and enclosures (intended to contain an explosion), or via pressurization or purging (intended to isolate the explosive gas from the electrical equipment). Intrinsically safe apparatus cannot replace these methods in all applications, but in many cases can provide significant cost savings in installation and maintenance of the equipment in a hazardous area. The basic design of an intrinsic safety barrier uses diodes to limit voltage, resistors to limit current and a fuse.

Gravity Based Inclinometer Technology: Liquid Capacitive Basics

Liquid Capacitive Gravity Based Inclinometer Basics:

The sensing element of Rieker inclinometers use liquid capacitive technology, which is based on gravity. The best way to understand how they work is to think of a disc-like cavity that is half filled with a dielectric liquid. One of the sides of the cavity has an etched conductor plate that is used to form one of the conductors of a variable parallel plate capacitor. The liquid along with the other side of the cavity forms the other plate of the capacitor. In operation, the sensor is mounted so that the disc is positioned perpendicular to the ground (vertically mounted). Gravity then acts on the liquid pulling it down in the cavity forming a semi-circle. As the sensor is rotated the liquid remains in this semi-circular pattern covering a different area of the etched plate. This change in area results in a change in the capacitance. The change in capacitance is then electronically converted into an output signal that is linear with respect to in the input angle.

The liquid capacitive technology also has a very low-frequency response bandwidth's - typically 3Hz - which means that their response times are much slower than most spring mass based inclinometers, around 250mSeconds. The benefit of these small bandwidths helps to dampen spikes in the output in applications with lots of vibrations and shock. The inclinometers are made with extremely tight cavities to provide even more damping, compared to other liquid based units where the liquid is known to "slosh" around. All Rieker units are completed encapsulated providing shock and vibration protection. They contain no moving mechanical parts. Only the liquid is free to move making them extremely rugged for harsh environments. This design offers shock protection in excess of 10,000g. Some have built in filtering or come in metal boxes with additional capabilities (SB1i or SB1U).

Tuesday, August 08, 2006

Laboratory measurement of posture allocation and physical activity in children.

Medical Science Sports Exercise Study Originally published October 2005

PURPOSE: The purpose of this study was to validate the combined use of inclinometers and accelerometers to measure body posture and movement in children in a laboratory setting.

* Lanningham-Foster LM,
* Jensen TB,
* McCrady SK,
* Nysse LJ,
* Foster RC,
* Levine JA.

Endocrine Research Unit, Mayo Clinic, Rochester, MN 55905, USA.

METHODS: We performed two separate experiments.

In the first experiment, we tested the hypothesis that four inclinometers (tilt sensors) could be used to capture body posture in children. We observed and recorded body posture in eight healthy children (mean +/- SD; body mass index (BMI), 18 +/- 3 kg x m(-2)) on 2880 occasions and compared these records with the inclinometer data.

In the second experiment, the hypothesis was that two inclinometers could be used to determine whether 18 children (BMI, 21 +/- 5 kg x m(-2)) were sedentary. We observed and recorded sedentariness (sitting/lying compared to standing) on 5575 occasions and compared these records with the inclinometer data.

In both of these experiments, we also addressed the hypothesis that accelerometer output, when measured at varying velocities, correlated with walking energy expenditure. RESULTS: In experiment 1, body posture was correctly identified in 2880 out of 2880 inclinometer measurements. In experiment 2, sedentary behavior was correctly identified in 5575 out of 5575 occasions. For the entire group, acceleration and body weight correlated well with energy expenditure (r2 = 0.84).

CONCLUSION: The inclinometer-accelerometer system that we tested can be used to measure body posture and movement. We can measure sedentary behavior using two inclinometers instead of four inclinometers. This monitoring system may be useful for measuring energy expenditure, body posture, and physical activity in children.

PMID: 16260984 [PubMed - indexed for MEDLINE] www.pubmed.gov is a service provided by the US National Library of Medicine and the National Institutes of Health

Friday, July 07, 2006

Rugged Inclinometers for Construction and Off-road Equipment

The H4 Series of rugged inclinometers provide single axis inclination sensing in a rugged environmentally protected Zinc metal housing. This is an improved line of inclinometers (or tilt indicators) designed for off-road forklifts, material handlers, and equipment with aerial booms.

Available with 0-5V Analog or Digital Serial (RS232) Outputs, the unit incorporates a liquid capacitive sensing element for exceptional vibration damping with integrated temperature compensation. Depending on the required accuracy, two levels of temperature compensation are available. Angle ranges are ±30º, ±45º, and ±70º.

The H4’s Serial Output (RS232) transmits the angle, in decimal format, in a continuous stream of readings - 250msec per reading, 9600 baud, 8 data bits, no parity, 1 stop bit.

The H4 has a common footprint (with adjustment slot) making it easy to retrofit or field-replace less durable sensors. Applications include boom angle indication and platform leveling - built for rugged harsh environments to provide accurate angle monitoring.

Tilt indicators alert operators to dangerous situations

from an article published in the June issue of Equipment World Magazine, under MACHINE ENHANCEMENTS, page 71.

Tilt indicators alert operators to dangerous situations
Rieker Electronics makes several products that improve the ability of operators to detect potential roll-over situations. Its H4 Series inclinometers provide single axis sensing and are available with analog or digital outputs. Rieker’s RDI Series digital inclinometer is available as a display or remote sensor package for off-road, rough-terrain construction vehicles.

Equipment World Magazine is the first source of information for today's active contractor.

Equipmentworld.com is a news and e-commerce website for construction contractors, equipment manufacturers and dealers and providers of services and supplies to the construction industry.

Friday, January 20, 2006

Inclinometer by Leonardo da Vinci

- amazing inclinometer fact -



This instrument was used for controlling the air position of the flying machines devised by Leonardo. For the machine to reach the horizontal position indispensable for certain flight conditions, the small ball in the bell jar must be positioned right in the middle of the inclinometer. The bell glass is for preventing the wind from affecting the ball.



Codex Atlanticus, folio 1058 former folio 381 r.a.
Drawing extracted from the book, Il Codice Atlantico di Leonardo da Vinci nella biblioteca Ambrosiana di Milano (Editore Milano Hoepli 1894-1904.)
The original Leonardo drawing is kept in the Biblioteca Ambrosiana

http://www.ambrosiana.it/ita/index.asp

The upper portion of the folio shows drawings to do with weights applied to scales, and experiments for measuring the robustness of screws. In the lower portion is a drawing of the inclinometer, which can be dated between 1483 and 1486. Next to this instrument - devised for measuring verticality and used for flying - there is the caption, non ci vuol dare il vento "there has to be no wind" and also Questa palla dentro al cerchio ha esser quella che ti farà guidare lo strumento diritto o torto, come vorrai, cioè quando vorrai andare pari, fa che la palla stia nel mezzo del cerchio, e la pruova te lo insegnerà "The ball in the middle of the circle will enable you to direct the course of your machine. That is, whenever you want to fly horizontally make sure the ball is in the middle of the circle. Give it a try and you'll see".

Wednesday, January 11, 2006

Inter-observer reproducibility of measurements of range of motion in patients with shoulder pain using a digital inclinometer

Research article

BMC Musculoskeletal Disorders 2004, 5:18 doi:10.1186/1471-2474-5-18

Reproducible measurements of the range of motion are an important prerequisite for the interpretation of study results. The digital inclinometer is considered to be a useful instrument because it is inexpensive and easy to use. No previous study assessed inter-observer reproducibility of range of motion measurements with a digital inclinometer by physical therapists in a large sample of patients.

Click link above to continue reading the rest of the article.

USE OF AN INCLINOMETER FOR CONTINUOUS RECORDING OF HEAD OF BED POSITION

...as pubished on Chestjournal.org under Critical Care Treatment
Wednesday, November 2, 2005, 12:30 PM - 2:00 PM

USE OF AN INCLINOMETER-DATA LOGGER TOOL FOR CONTINUOUS RECORDING OF HEAD OF BED POSITION IN PATIENTS UNDERGOING MECHANICAL VENTILATION
Boaz A. Markewitz, MD*, Jeanmarie Mayer, MD, Dwayne Westenskow, PhD and Stephanie Richardson, PhD

University of Utah, Salt Lake City, UT

PURPOSE: Ventilator-associated pneumonia remains a common problem with attributable morbidity and mortality. Several preventive strategies are recommended including semi-recumbent positioning (head of bed angle at 30 degrees or above) in the absence of contraindications. Most studies that describe this practice, however, assess head of bed (HOB) position infrequently (i.e., often just once per day). As such, the data provided may not be reflective of what is occurring over longer time intervals. We sought to determine the angle of the HOB once per minute in patients receiving mechanical ventilation.

METHODS: The HOB angle was measured using an inclinometer (Rieker Electronics, Inc.; Folcroft, PA) and the information was stored in a data logger (Onset Computers; Bourne, MA) until it was downloaded. The inclinometer-logger system was housed in a box which attached to the undersurface of the head of the bed. Calibration curves for each of six inclinometer-logger boxes was obtained between 0 to 60 degrees at 5 degree intervals. Each morning during the week a box was placed under the head of the bed of an intubated patient if the clinical team expected the patient to remain intubated at least for that day. Data was collected until the patient was extubated.

RESULTS: 30 intubated patients were evaluated over a two month period. The median time of intubation was 47 hours (range 2-340 hours). The mean HOB angle for each of the 30 patients ranged from 0-27 degrees (median 21 degrees). The median percentage of time spent at or above a 30 degree angle was 3% (range 0-62%). The median percentage of time spent at or above a 45 degree angle was 0% (range 0-2%).

CONCLUSION: This study indicates that semi-recubancy is rarely achieved in patients receiving mechanical ventilation. We have developed a tool which allows for continuous measurement of HOB angle. This method of monitoring shows promise as an assessment tool to improve patient care and provide feedback to the healthcare team.

CLINICAL IMPLICATIONS: There is much room for improvement in pneumonia prevention.

DISCLOSURE: Boaz Markewitz, None.
COPYRIGHT © 2005 by the American College of Chest Physicians.

Monday, January 09, 2006

Subsurface drainage pays big dividends

Mar 1, 1999 12:00 PM, Joan Olson

"GPS yield maps and precision farming have created a demand for tile drainage never before seen," says Don Sisson, executive director of the Indiana Land Improvement Contractors Association. "Farmers are checking their yields foot by foot and can see the yield differences between tiled and not tiled ground. Many farmers are finding their highest yields over the tile lines and their lowest yields halfway between the tile lines."

Yields are higher because drainage provides good agronomic conditions, mellower soil, deeper plant root zone, less compaction, more timely planting to maximize the growing season, earlier harvest, less surface soil erosion and less runoff of nutrients such as phosphorous.

Measurable payoff. Pat Feldpausch, Fowler, MI, saw a 30-bu. corn yield drop midway between his 50-ft. tile spacings in one field he farms. He decided to tile the rest of the field on 30- to 35-ft. spacings. In other fields, his yield data show that 100-ft. spacings drain just fine. The optimum distance between tile lines varies depending on soil type, topography and other factors that influence how quickly water moves through the soil.

Feldpausch has found that tile pays off in dry years as well as wet years. "We had a drought this year - only 4 in. of rain during the whole growing season. One tiled field yielded 145 bu./acre despite the drought. Another field with the same soil type that wasn't tiled yielded only 100 to 110 bu./acre," he says. One reason tile benefits crops in dry years is that lowering the water table in the spring causes plants to develop a deep and vigorous root zone.

Feldpausch rents or custom farms the majority of the land he farms, and he invests his own money to tile the ground. "It's not uncommon for even 100-ft. spaced tile to increase yields by 50% in these poorly drained fields," he claims.

Trend toward closer spacings. The interest in closer spacing between tile lines is greatest in northern states where the growing season is short and being able to plant several days earlier pays tremendous dividends. In Ontario, Canada, 35- to 40-ft. spacings between tile lines are most common, whe reas in Illinois and Indiana it's common to find 100-ft. spacings. In all areas of the country, farmers are using precision farming yield data to help them determine the best drainage systems for their farms.

Indeed, precision farming's biggest payback has come from identifying needed drainage improvements, notes Don Larson, of Larson Systems, Ames, IA, a provider of precision farming mapping software and interpretation services. He knows about tiling firsthand from his family's farm in Story City, IA, where the purchase of a used, open-trencher tiling machine in 1993 gave them the highest return of any other piece of farm equipment that they have ever owned. "We achieved a 30- to 40-bu. corn yield increase by adding drainage tile," says Larson. "We started putting the tile in at 120-ft. spacings, but when our yield maps showed a yield reduction halfway between adjacent lines we went to 60-ft. spacings. Ultimately, we found 90-ft. spacings are right for our heavy gumbo soils."

For Chip Kepford, Marion, OH, the GPS yield map indicated he should spot tile rather than systematically tile every 50 ft. in one of his fields. "The map identified areas of the field that naturally drained and where it would have been hard to recoup our investment for tile," Kepford explains.

In some areas, demand for tiling has outstripped local contractors' capacity. Rather than wait a year or more to get their tiling done, some farmers have purchased their own add-on pull-behind tile plows. These plows can be mounted on a tractor or pulled behind it. They range in cost from $2,600 to $20,000 and are handled by manufacturers of small machinery. To assist with proper grade control, a laser system can be purchased for $10,000 to $20,000. A tile cart will cost $3,000 to $5,000. Labor, backhoe and machinery costs also need to be figured into the equation.

Parrish Farms, Millersport, OH, purchased a Johnson Drainage Plow with 6-ft. depth capability in November 1997 and has put in 170,000 ft. of tile since then. "I don't think farmers should buy this equipment and think they will save a lot of money over a contractor," says Ed Parrish. "There are a lot of costs besides the plow. A quality contractor will put the tile in as cheap or cheaper than you can yourself. For us it wasn't about saving money. It was a matter of getting the job done when there was no way to get it done otherwise."

Jerry Bulmahn is a former tiling contractor from Decatur, IN, who now farms 2,200 acres. In 1989 he purchased a tile plow with a 6-in. tile boot capable of 4-ft. depth from Farm Drainage Plows, also known as Wurdinger Tile Plow. "We have tiled 500 acres on our own farm with it. Three people can generally put in 6,000 ft. in a 10-hr. day. I'd put this plow up against any contractor's plow," says a satisfied Bulmahn. He claims that the tile plow paid for itself in the first year.

Bulmahn says the biggest problem for most farmers interested in doing their own tiling is to find a contractor to install the main outlets. "A contractor isn't eager to come in and do the mains and not the laterals. You'll be put at the bottom of their list," says Bulmahn. He suggests that two to three farmers work together and share labor and expenses to make the investment more practical. He also recommends planting winter wheat on the ground you want to tile so you have a longer window for finishing the work.

Brent Sharp, Maynard, IA, is a farmer and a tiling contractor. He operates a mid-size Johnson Drainage Plow with a laser. "Our laser takes it right where we want it to go," says Sharp. His GPS yield monitor has shown that corn yield from tiled ground is anywhere from 30 to 100 bu. more than the corn yield from undrained ground.

Add your name to the list. "Pull-behind tile plow sales are being made to farmers in areas where contractors have been slow to expand and offer competitive pricing for pattern tiling," says contractor Roger Ellingson, Ellingson Drain-age, West Concord, MN. His 20-employee business installs 4 to 5 million ft. of tile each year. "A contractor with two employees and a trencher that installs 300,000 ft. a year can't shift gears fast enough to meet the demand for high-speed installation. Farmers don't want to wait because they see the tremendous value of tiling. If they are put on a two- or three-year waiting list, or if prices are in the $600 to $800/acre range, they'll look for an alternative."

A job for the experts? He and many other contractors question whether most farmers can achieve good results with a pull-behind tile plow. They question whether the engineering, depth control and grade control are adequate on these machines, which cost just a fraction of the $200,000 to $500,000 that contractors spend on a trencher or self-propelled tile plow. They also question whether an inexperienced operator is capable of planning an efficient system and maintaining grade.

USDA-ARS ag engineer James L. Fouss, Baton Rouge, LA, was one of the early developers of large, self-propelled tile plows and laser grade control systems now used by tiling contractors. He states, "You can't expect to install tile properly with a modified subsoiler. I'm leery of them being able to maintain proper grade as the soil changes from hard to soft across the field. The weight of the machine is not great enough to overcome the differences in soil resistance."

Contractor Ellingson agrees: "I've had instances where the farmer felt he had done a good job of installing a line himself, but when he had us probe the tile and check it for accuracy, we found areas with dips, humps or no grade at all. That means that the tile will not function at full efficiency and in 5 to 15 years the tile may silt in and plug up. The line could fail in 10 years when it should last 100 years."

Research results in the Corn Belt show that drainage improves yields substantially on poorly drained soils. Long-term studies conducted in Indiana and Ohio showed that in fields with subsurface drainage, corn yield was an average of 14 to 23 bu./acre more and 20 to 30 bu./acre more, respectively, than yield in fields without drainage. In Ohio, a 7 to 14 bu./acre soybean yield advantage was realized from subsurface drainage.

Growers of Parrish Farms, Millersport, OH, have been systematically tiling all of their owned acreage for more than 20 years. "We have many years of production records. We know that drainage pays and it pays big," says Ed Parrish. "In critical circumstances, tiling gives a 30% return on investment and normally you can expect a 10 to 12% return every year. It's a continuing benefit."

Return on investment. Advanced Drainage Systems (ADS), in Columbus, OH, is the largest manufacturer of drainage pipe. The company's G.R.O.W. Analysis software determines annual and cumulative cash flow, return on investment, payback period and break-even production per acre for drainage tile installations. "The return on investment for a drainage system is usually more than 12% a year. The usual payback period is 7 to 10 years," says Kevin Rapp, agriculture market manager, ADS.

Using the software, a grower also can compare the return on investment for purchasing a new tract of land or improving drainage on existing land. "The return on investment for buying ground is very low. Installing drainage to improve yields on existing land is a much more productive use of investment capital," Rapp adds. This software is available to growers at no cost from their local ADS sales representative. Call 800/821-6710.

Costs vary. Tile instal-lation costs vary tremendously across the country and even within a state.

A 1999 Indiana Land Improvement Contractor's Association price survey showed that the cost of 4-in.-dia. pipe installed ranges from $0.45 to $2.00/ft. According to Mike Cook, executive director of Michigan Land Improvement Association, the cost for installing 4-in. pipe on 50-ft. spacings ranges from $300 to $500/acre in different parts of Michigan. The cost for the same system in some parts of Iowa and Illinois could cost as much as $800/acre.

Each job is unique and many factors go into cost calculations, including soil texture and structure, soil permeability, terrain, topography, rocks, distance to the main outlets, size of the mains, number of acres tiled, type of tiling machine and area competition. Because large, self-propelled tile plows can install 120 to 140 ft./min., twice as much tile per minute than open trenchers, contractors with tile plows are generally more competitive for large jobs such as pattern tiling entire fields.