Truck scale
Encyclopedia
Load cell
A load cell is a transducer that is used to convert a force into electrical signal. This conversion is indirect and happens in two stages. Through a mechanical arrangement, the force being sensed deforms a strain gauge. The strain gauge measures the deformation as an electrical signal, because the...
Weight certification
Commercial scales have to be National Type Evaluation Program (NTEP) approved or certified. The certification is issued by the National Conference on Weights and MeasuresNational Conference on Weights and Measures
The National Conference on Weights and Measures is a not-for-profit corporation dedicated to developing and regulating the United States technical standards for weights and measures...
(NCWM), in accordance to the National Institute of Standards and Technology
National Institute of Standards and Technology
The National Institute of Standards and Technology , known between 1901 and 1988 as the National Bureau of Standards , is a measurement standards laboratory, otherwise known as a National Metrological Institute , which is a non-regulatory agency of the United States Department of Commerce...
(NIST), "Handbook 44" specifications and tolerances, through Conformity Assessment and the Verified Conformity Assessment Program (VCAP)
Legal for trade
Handbook 44: General Code paragraph G-A.1.; and the NIST Handbook 130 (Uniform Weights and Measures Law; Section 1.13.) define Commercial Weighing and Measuring Equipment as follows;NTEP approved scales are generally considered those scales which are intended by the manufacturer for use in commercial
applications where products are sold by weight. NTEP Approved is also known as Legal for Trade or complies with Handbook 44. NTEP scales are commonly used for applications ranging from weighing coldcuts at the deli, to fruit at the roadside farm stand, shipping centers for determining shipping cost to weighing gold and silver and more.
Types
- Electronic (deep pit type)
- Electronic (shallow pit)
- Electronic (pitless type)
- Digital (deep pit type)
- Digital (shallow pit)
- Digital (pitless type)
- Rail Weigh bridges
- Movable Weigh Bridge
- Mechanical weighbridge
- Mechanical (digital type)
- Electro-mechanical
- Portable weigh bridge
- Axle scales
- Portable ramp end scales
Design
In earlier versions the bridge is installed over a rectangular pit that contains levers that ultimately connect to a balance mechanism. The most complex portion of this type is the arrangement of levers underneath the weigh bridge since the response of the scale must be independent of the distribution of the load. Modern devices use multiple load cell
Load cell
A load cell is a transducer that is used to convert a force into electrical signal. This conversion is indirect and happens in two stages. Through a mechanical arrangement, the force being sensed deforms a strain gauge. The strain gauge measures the deformation as an electrical signal, because the...
s that connect to an electronic equipment to totalize the sensor inputs. In either type of semi-permanent scale the weight readings are typically recorded in a nearby hut or office.
Many weighbridges are now linked to a personal computer
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
which runs truck scale software
Truck Scale Software
Truck Scale Software is a class of software pertaining to the collection of transactional scale weighment data. Specifically for truck scales used to weigh heavy trucks, light trucks, or other commercial vehicles...
capable of printing tickets and providing reporting features.
Usage
Truck scales can be used for two main purposes:- Selling or charging by weight over the bridge (Trade Approved)
- Check weighing both axle weights and gross vehicle weights. This helps to stop axle overloading and possible heavy fines.
They are used in industries that manufacture or move bulk items, such as in mines or quarries, garbage dumps / recycling centers, bulk liquid and powder movement, household goods, and electrical equipment. Since the weight of the vehicle carrying the goods is known (and can be ascertained quickly if it is not known by the simple expedient of weighing the empty vehicle) they are a quick and easy way to measure the flow of bulk goods in and out of different locations.
A single axle truck scale or axle weighing system can be used to check individual axle weights and gross vehicle weights to determine whether the vehicle is safe to travel on the public highway without being stopped and fined by the authorities for being overloaded. Similar to the full size truck scale these systems can be pit mounted with the weighing surface flush to the level of the roadway or surface mounted.
For many uses (such as at police over the road truck weigh stations or temporary road intercepts) weigh bridges have been largely supplanted by simple and thin electronic weigh cells
Load cell
A load cell is a transducer that is used to convert a force into electrical signal. This conversion is indirect and happens in two stages. Through a mechanical arrangement, the force being sensed deforms a strain gauge. The strain gauge measures the deformation as an electrical signal, because the...
, over which a vehicle is slowly driven. A computer records the output of the cell and accumulates the total vehicle weight. By weighing the force of each axle it can be assured that the vehicle is within statutory limits, which typically will impose a total vehicle weight, a maximum weight within an axle span limit and an individual axle limit. The former two limits ensure the safety of bridges while the latter protects the road surface.