R134/2006-A-CZ1-25.01

Important note: Apart from the mention of the Certificate's reference number and the name of the OIML Member State in which the Certificate is issued, partial quotation of the Certificate and of the associated OIML type evaluation report(s) is not permitted, although either may be reproduced in full.

1 INSTRUMENT NAME AND DESCRIPTION

PW 134 is a portable weighing instrument designed for determining the weight of wheels, axles, and the total weight (gross vehicle weight) of road vehicles.

1.1 Weighing instrument modules

The weighing instrument consists of the following parts (modules):

• A pair of weighing platforms, which are load receptors with integrated load cells.

• Levelling pads (usually plastic mats) for installing the portable weighing instrument on the roadway surface. Alternatively, the levelling pads can be replaced by inserting the weighing platforms into a base frame embedded in the roadway surface.

• Indication unit with legally relevant software (LRSW): WSERVER, WTERMINAL, and Firmware PSU.

2 MAIN METROLOGICAL CHARACTERISTICS

Table 1: PW134 metrological characteristics

Min and Max, as shown in Table 1, determine the range of weight capacity per wheel of the vehicle ( $ \mathrm{M i n}{\mathrm{w h e e l}} $ $ \mathrm{M a x}{\mathrm{w h e e l}} $ ).

For the weighing capacity range of one axle, the following formula applies:

$$ \mathrm {M i n} _ {\mathrm {a x l e}} = 2 \mathrm {x} \mathrm {M i n} _ {\mathrm {w h e e l}} $$

$$ \mathrm {M a x} _ {\mathrm {a x l e}} = 2 \mathrm {x} \mathrm {M a x} _ {\mathrm {w h e e l}} $$

The weighing range for the total vehicle weight (Gross vehicle weight - GVW) is determined as the product of the weighing range of one axle and the maximum number of weighable axles $ \left( \mathrm{A}_{\mathrm{m a x}} \right) $

$$ \mathrm {M a x} _ {\mathrm {G V W}} = \left(2 \mathrm {x} \mathrm {M a x} _ {\mathrm {w h e e l}}\right) * \mathrm {A} _ {\max } $$

In the default configuration of PW 134 scales, the parameter $ A_{\mathrm{m a x}}=1 6 $ . The value of $ A_{\mathrm{m a x}} $ can be adjusted during the manufacturing process in the range $ 1 6 \leq A_{\mathrm{m a x}} \leq 9 9. $

3 WEIGHING INSTRUMENT DESIGN

3.1 Mechanical design of the load receptor

The weighing platforms, which are the load receptors of the PW 134 weighing instrument, are sandwich structures consisting of a base plate fitted with strain gauge load cells and a bottom cover plate with supports for the load sensors.

A PSU module (Platform Scale Unit) with an integrated A/D, temperature sensor and a platform tilt sensor are inbuilt into the weighing platform as shown in the following Figure:

3.2 Electronics

The weighing instrument electronics consist of three hardware modules:

Table 2: Hardware modules

3.2.1 Detachable electronic units

A Communication unit for wireless data transmission or an Indication unit can be connected to the weighing platform. Both units contain a rechargeable battery power source.

Table 3: Detachable electronic units

3.3 Principle of operation

Low-level signals from the load sensors are routed through junction boards to a single output with a load cell bridge function. This is connected to the input of the PSU module, converted to digital signal and transmitted via secured protocol to the Indication unit over the RS-485 bus. Each weighing platform can be connected to:

• another weighing platform (multiple platforms can be chained in this way),

• or a Communication unit with a CBU module,

• or an Indication unit, which contains both a CBU module and an indicator.

3.4 Wired or wireless communication

EIA-485 bus is used for chain connection of weighing platforms leading to the Indication unit. Connection is established by cable or wirelessly by Bluetooth, as shown in the following diagrams:

3.5 Controlled weighing area

Weighing instrument installation instructions are based on OIML R 134:2006 Annex B clause and are further specified in manufacturer's User manual.

3.5.1 Weighing zone with weighing platforms laid on the roadway surface

When the weighing platforms are placed on the road surface, the levelling of the weighing platforms is ensured by a set of levelling pads or levelling mats placed in front of and behind the weighing platforms. The length of the levelling mats shall be sufficient to ensure that all the wheels of the individual vehicles in the vehicle combination remains at the same level during weighing - as shown in the Figure 5a,b:

3.5.2 Weighing zone with weighing platforms in the level of road surface

The base frame lined with a steel angle is used to place the weighing platforms at the level of the road surface of the weighing zone. The bottom of the foundation must provide support for the weighing platforms over the entire surface of the bottom plate. Frame is levelled to a plane in both longitudinal and transversal directions. The minimum length of the weighing zone, in the centre of which the base frame with weighing platforms is placed, is determined by the longest wheelbase of the vehicle being weighed.

4 SOFTWARE

The legally relevant software of the scales and its security meet the requirements of the WELMEC 7.2:2023 software guide. The software of the Indication unit is based on a client-server architecture. WSERVER application acts as the server, to which external client applications can connect. The structure of the legally relevant software - LRSW and the software of external clients is shown below:

4.1 Software modules and their functions

4.1.1 PSU Firmware

The PSU firmware is stored in the integrated secured EEPROM memory of the PSU module.

The PSU firmware is stored in the integrated secured EEPROM memory of the PSU module. PSU modules are paired with a specific indication unit during the manufacturing process by a unique key that allows the paired PSU module to communicate only with that specific indication unit.

4.1.2 OS Linux - Debian distribution with LinuxRT extension

The single chip computer (SoC) of the indication unit runs the closed Linux Debian operating system with the LinuxRT extension. Access to the operating system functions and interfaces of the SoC computer beyond selected functions of the weighing device is prohibited at the operating system level.

4.1.3 WSERVER

The WSERVER application establishes and controls communication with paired PSU modules via the UART interface (TTL or EIA-485). The indicator unit with LRSW WSERVER acts as the Master device on the bus.

4.1.3.1 WSERVER LEGALLY RELEVANT FUNCTIONS

• Weighing in automated mode - WSERVER control the process of weighing-in-motion and performs data collection from paired PSU units.

• Storing weighing records in the internal integrated DSD memory.

• Selecting LRD from DSD memory and displaying them on the indicator unit display. The WTERMINAL application provides the display's graphical interface and keyboard commands.

• During calibration and verification process, WSERVER controls saving of LRF parameters created by the Service client WSERVICE as described in article 4.5.

Ceský metrologicky institut

-3-

4.1.4 WTERMINAL

WTERMINAL is LRSW serving HID devices - it ensures the display of LRD provided by the WSERVER application on the indicator unit display, menu navigation, and operation of the indicator unit keyboard.

4.2 Software identification by version number and CRC checksum

LRSW applications are identified by version number and CRC checksum. Software identification by version number:

• WSERVER: WSRV: 1.01.02

• WTERMINAL: WTRM: 1.01.03

• PSU Firmware: PSU 01-nn: 1.07.00 (where "nn" is the number of paired platforms)

The CRC checksum has 8 characters in hexadecimal format:

• WSRV: 42A43767

• WTRM: D7142A48

• PSU 01-02: 3C376769,4E234828

When the indicator unit starts, the CRC of LRSW WSERVER, WTERMINAL, and the PSU EEPROM memory data area are calculated and then compared with the stored value. If the values do not match, an error message is displayed and weighing is disabled.

The display of LRSW version numbers and their CRCs are included in the indicator's start-up sequence. These data are also accessible during system operation from the indicator user menu.

4.3 Adjustment number mechanism

To prevent unauthorised changes to LRF parameters, the system is further protected by an adjustment number mechanism. Changes to LRF parameters always result in a new adjustment number generated by the LRSW WSERVER application, which is displayed upon start-up of the indication unit:

4.4 Storage and displaying of Legally relevant data

LRD generated during the weighing process are automatically stored in the integrated DSD memory of the indication unit upon completion of weighing. External access to the DSD memory (excluding access controlled by the LRSW WSERVER application) is disabled.

The data in the DSD memory is secured against intentional and unintentional changes by a checksum. After each write to the DSD memory, the checksum value is recalculated and stored in the LRSW WSERVER configuration.

Quantity of stored weighing records is set to 1 000 000 by default (can be changed in factory parameters).

Quantity of stored weighing records is set to 1000000 by default (can be changed in factory parameters). Viewing records in the DSD memory is possible by client's query to WSERVER. WSERVER reply with data dump from the DSD to display of the Indication unit or to communication interface.

4.5 Service client WSERVICE and adjusting of LRF parameters

The WSERVICE software client provides functions for servicing and calibration of the scales, and adjusting their LRF parameters. Writing LRF parameters to the DSD memory is performed exclusively by the WSERVER.

Changes to LRF parameters can be applied only when 'CAL' switch is activated on the weighing platform.

5 TECHNICAL DATA

5.1 Weighing platforms technical data

Weighing platforms are manufactured in several types, differing in max. capacity and dimensions of active surface:

Dimensional variability resulting from the customisation of mechanical parts do not affect the metrological characteristics or LRF of the scales.

The Length of the platform refers to the dimension measured in the direction of vehicle ride. The Width of the platform refers to dimension measured across the direction of vehicle ride.

5.2 Power supply

The scales are powered by direct current from an internal battery in the scale display unit or from an external adaptor (100-240 V, 50-60 Hz/12 V DC), which also serves as a charger of the internal battery.

5.3 Interfaces and optional peripheral devices

The interfaces are described in Table 3.

PW134 weighing instrument can be equipped with optional auxiliary devices providing additional functions of the weighing instrument - i.e. printing device, external display, ANPR camera, various types of vehicle detection devices etc.

These devices are connected to and controlled by external SW client running on an external device, typically on a PC with Windows OS or a tablet with Android OS.

Peripheral devices and its data do not affect the LRD of the weighing instrument.

6 CALIBRATION, VERIFICATION AND SECURING OF THE WEIGHING INSTRUMENT

The metrological tests must be carried out according to national applicable regulations.

6.1 Securing components and verification marks

6.1.1 Securing the calibration switch on weighing platforms

The calibration switch 'CAL' cover is secured with a self-adhesive verification mark placed across one of the cover screws, as shown in Figure 9 on the left.

6.1.2 Main instrument label

The main instrument label with complete descriptive markings is located on the weighing instrument's indication unit. The label complies with clause 3.9 of the international recommendation OIML R 134:2006. Following information are provided on the label:

The main label is secured with a verification mark.

6.1.3 Label on weighing platforms

Each of the weighing platforms is equipped with a label containing the basic platform parameters, the platform serial number, and the serial number of the indication unit with which the platform was paired during manufacturing.

The label is also secured with a verification mark.