VPG BHL Nobel AST 3P - User Manual

The BLH Nobel AST 3 is an analogue signal transmitter designed for industrial weighing and measurement applications using strain gauge transducers. It is available in two versions: AST 3B and AST 3P. The compact module is designed for easy installation on a DIN rail or a flat surface, requiring at least 10 mm of free space on each side when mounted.

Function Description

The AST 3 converts signals from strain gauge transducers into a measurable value, typically weight, and provides an analogue output. It also offers various set-up and calibration functionalities.

AST 3P (with display and function keys): This version features a display window and function keys for both set-up and measuring operations. It allows for direct interaction with the instrument for configuration and monitoring.

AST 3B (without display, for use with a control unit): This version is designed to operate in conjunction with a control unit, such as a PC running the deltaCOM software. Set-up and configuration for AST 3B are performed via serial communication.

The device supports both 4-wire and 6-wire transducer connections, with 6-wire recommended for longer cable runs or multiple transducers.

Important Technical Specifications

• Power Supply: 24 V DC. Continuous power supply is recommended to prevent moisture condensation in electronics and transducers.
• Transducer Input: Terminals 1-7 (8). Requires shielded cables routed at least 200 mm away from 230/380 V, 50/60 Hz power cables to avoid electromagnetic interference.
• Analogue Output: Terminals 24, 25. Provides a current or voltage signal corresponding to the measurement value. The cable shield should be connected to ground.
• Serial Communication: Terminals 19-23. Supports RS-485 on 2-wires or 4-wires with common earth (COM). Requires 120 ohm termination at both ends of the line.
• Measurement Unit: Configurable (e.g., kg).
• Resolution: Configurable, defining the number of decimals and the resolution of the last digit.
• Capacity: Defines the full-range weight value corresponding to the analogue output.
• Analogue Output Type: Configurable (e.g., 4-20mA).
• Calibration Types:
  • Data Sheet Calibration: Used when load cell data is available, and the load is evenly distributed without external disturbing forces. Requires input of conversion factor, number of transducers, rated load per transducer, and rated output per transducer.
  • Dead Weight Calibration: The most accurate method, requiring known weights (at least two-thirds of the scale capacity) for two calibration points.

Usage Features

Operating Mode (AST 3P): In normal operation, the AST 3P displays the current weight value, instrument address, and status of internal relays (R1/R2: On or Off). The function keys (+ and -) allow selection of different views:

• Weight value (normal view): Displays current measurement, address, and relay status.
• Zero setting: Displays weight and address, with a dedicated key for temporary zeroing. This zeroing is temporary and reverts to the last calibrated zero after power-off or reset.
• Analogue output: Displays weight, address, and the actual analogue output signal.
• Level settings: Displays switching levels for two supervising channels (if in use).
• Input signal: Displays actual input signal from transducers, address, and relay status.
• S/N:, Progr.: Displays instrument serial number and installed program name.

Zero Setting (Permanent): To perform a permanent zero setting (saved in memory), the instrument must be in set-up mode. This is useful if the scale equipment has changed.

1. Ensure the scale is unloaded.
2. Enter set-up mode by holding ESCAPE (⇧) for 2 seconds.
3. Enter password if required.
4. Navigate to 'Set zero' parameter using (+) key.
5. Press (-) to set the parameter value to zero.
6. Hold ENTER for 2 seconds to confirm.
7. Note the 'Zero offset' value (useful for replacement instruments).
8. Exit set-up mode and save changes.

Maintenance Features

Quick Set-up and Calibration: The AST 3P allows for quick set-up and calibration directly from its panel. For AST 3B, this is done via the deltaCOM software.

1. Access 'Quick set-up': From normal operation, hold ESCAPE (⇧) for 2 seconds.
2. Common Parameters:
   • Language: Selects the display language.
   • Measurement unit: Defines the unit for measurement values (e.g., kg).
   • Resolution: Sets the number of decimals for measurement values.
   • Capacity: Defines the instrument's full-range capacity.
   • Ana. output type: Selects the analogue output signal type (e.g., 4-20mA).
3. Calibration Type Selection: Choose between 'Data sheet' or 'Deadweight' calibration.

Data Sheet Calibration Procedure:

1. Conversion factor: Defines a constant to convert weight value to the data sheet unit (e.g., 9.80665 for kg to Newton).
2. Number of transducers: Total support points for the load.
3. Rated load: Rated load for one transducer in data sheet units.
4. Rated output: Rated output in mV/V for each transducer (0.00000 for fixed supports).
5. Set scale to zero: Unload the scale and set the weight value to zero.
6. Read zero offset: Note this value for future replacement.
7. Exit and save: Exit set-up mode and save changes.

Dead Weight Calibration Procedure:

1. Value cal. p.1: Set the known load for the lower calibration point (normally zero/unloaded scale).
2. Value cal. p.2: Load the scale with known weights (at least two-thirds of capacity) and set the value for the higher calibration point.
3. Transd.sign. p.1 & p.2: Read and note the transducer signals for both calibration points (read-only, useful for replacement).
4. Set scale to zero: Unload the scale and set the weight value to zero.
5. Read zero offset: Note this value for future replacement.
6. Exit and save: Exit set-up mode and save changes.

deltaCOM Software: For AST 3B, the deltaCOM software (included on a diskette) provides comprehensive set-up capabilities. It runs on Windows 95/98/2000/XP/NT4.0 and allows users to find, study, and edit all set-up parameters for AST 3 modules connected via serial communication.

Troubleshooting and Diagnostics: Error codes and corrections are detailed in the AST 3 Technical Manual (publication 600 232). This manual also covers advanced set-up options not included in the quick installation guide, such as password settings, filter adjustments, relay functions, analogue output adjustments, communication parameters, table calibration, and diagnostics.