1
1.0
Introduction
This manual contains operating and service procedures for both the PW 400 and PW 500 Portable Wheel
Weighers.
1.1
General Description
The PW 400 and PW 500 Portable Wheel Weighers are microprocessor controlled, hydraulically operated,
static weighers designed to measure weight applied anywhere within the weighing surface. The weighers are
packaged in a rugged, corrosion resistant, lightweight enclosure specifically designed to meet the demand of
daily outdoor operation.
The PW 400 and PW 500 are identical in operation. The main difference in the two models is the size of the
platform. The PW 400 platform is 10" x 11" to handle most standard truck tires, while the larger PW 500
platform at 13.5" x 11" is suitable for trucks with oversize tires or dual wheels. Both the PW 400 and PW 500
in 20,000 lb capacity x 50 lb display division models are NTEP certified Class IIII for commercial use.
Each weigher is powered by either a rechargeable or non-rechargeable battery. A variety of optional charging
units are available for the rechargeable models, allowing them to be charged from 110 VAC, 220 VAC, or 12
VDC power sources.
The units have 20-degree integral ramps that allow for easy drive-on/off and a nonskid bottom for operator
safety. Optional larger approach ramps are available to give a more gradual approach slope and longer
footprint.
Weighers can be used in one of two modes:
1. In Local mode, each weigher displays only its own load.
2. In Total mode, multiple weighers can be interconnected in series to allow as many as 30 units to be
used together. Each weigher displays the total weight of all interconnected weighers.
Initial calibration of each weigher is performed at the factory and no field adjustments are necessary.
Recalibration is necessary only after repair or replacement procedures.
1.2
Functional Description
The weight applied to the platform of the weigher undergoes a series of transformations before being dis-
played to the operator. The first transformation is the weight becoming a directed force transferred by a series
of mechanical links to a single hydraulic load cell fitted with an electronic pressure transducer.
The load cell contains a non-compressible fluid that exhibits a known viscosity over the operating pressure
and temperature range. Any change in pressure is detected by the pressure transducer which supplies an
electrical signal that is proportional to the weight applied to the weigher platform.
The electrical signal is converted to a digital format that is transmitted to the microprocessor. The micropro-
cessor decodes the digital signal and transmits the weight information to the display.
