BRUEL & KJAER 1526 - User Manual

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Overview

Function Description
Important Technical Specifications
Usage Features
Maintenance Features

The Brüel & Kjær 1526 Strain Indicator, along with its accessories, the Multipoint Selector and Control Type 1544 and Multipoint Selector Type 1545, forms a comprehensive system for accurate strain measurements.

Function Description

The Type 1526 Strain Indicator is a direct-reading digital instrument designed for measuring static strain and dynamic strain up to 300 Hz. It can be used with a wide range of strain gauges and strain-gauge transducers in quarter-, half-, or full-bridge configurations. The instrument allows monitoring of up to 5 strain-gauge bridges.

For applications requiring more extensive monitoring, the 1526 can be integrated with a Multipoint Selector and Control Type 1544 and up to 39 Multipoint Selectors Type 1545. This expanded system can monitor up to 400 bridge configurations. The Type 1544 also features an output socket for digital data transfer via the B&K Interface Bus to other digital recorders and processors.

The Strain Indicator employs a carrier frequency system to excite the measuring bridge, which effectively eliminates problems associated with DC systems, such as thermocouple effects and electrical/magnetic noise. This system also enables the use of a low bridge excitation voltage, minimizing heating effects on strain gauges.

Important Technical Specifications

Strain Indicator Type 1526:

Bridge Excitation: 0.3 V, 1 V, and 3 V (3 kHz square wave).
Ranges: ±199.9 µε, ±1999 µε, ±19990 µε (±199.9 µε only with 3 V excitation).
Gauge Factor: Continuously adjustable from 1.00 to 10.00 via a ten-turn potentiometer.
Accuracy:
- Without external calibration bridge: ±0.5% ±1 digit for gauge factor < 2; ±0.25% ±1 digit for gauge factor > 2.
- With external calibration bridge: ±0.1% ±1 digit.
Linearity: ±1 digit.
Noise on Display: ±1 digit.
Temperature Drift: <0.05% per °C.
Bridge Balance: Balances up to ±10000 µε with gauge factor 2.00 and resistance 120 Ω. Balance resolution is switchable (±2%, ±0.6%, ±0.4%, and ±0.1%).
Filters: Low-pass filters with 3 dB limits at 3 Hz, 30 Hz, and 300 Hz (12 dB/octave roll-off).
Rectifier: Average (response time 30 ms), Peak Hold (decay rate 1 digit per 10 s).
Outputs:
- Output 1: ±0.7 V to ±4 V for maximum reading on display, with offset possibility of ±4 V. Rg = 220 Ω.
- Output 2: ±10 V for maximum reading on display. Rg = 220 Ω.
- Digital Output: 17 data lines for 3 full and 2 half BCD characters, sign, decimal point, and overload indication. TTL levels.
Display: 7-segment neon gas discharge, 3 1/2 digits with plus/minus sign.
Power Supply: 100, 115, 127, 150, 220, 240 V AC, ±10%, 50 to 400 Hz.
Power Consumption: 10 W.
Operating Temperature: +5°C to +40°C.
Humidity Range: 0 to 90% relative humidity.
Dimensions (A cabinet): Height: 133 mm (5.25 in), Width: 430 mm (16.9 in), Depth: 200 mm (7.9 in).
Weight: 4.6 kg (10 lb).

Multipoint Selector and Control Type 1544 & Multipoint Selector Type 1545:

Bridge Connections: 10 measuring points per unit, configurable as full, half, or quarter bridges (with adaptor).
Bridge Excitation: 0.3 V, 1 V, and 3 V, derived from the 1526.
Bridge Balance: Up to ±10000 µε with gauge factor 2.00 and resistance 120 Ω. Resolution switchable (±2%, ±0.6%, ±0.4%, and ±0.1%).
Measuring Accuracy (with 120 Ω gauges and 1 or 3 V excitation):
- Relative to 1526: ±0.2%.
- Relative to any measuring point in the same Selector: ±0.1%.
Step Intervals (controlled by 1544): 0.1 s, 0.5 s, 1.0 s, 2.0 s, 5.0 s, and 10.0 s. Accuracy: ±5%.
Digital Input (1544 only): BCD coded strain levels and measuring point identification numbers.
B&K Interface Bus (1544 only): ASCII coded strain levels and point identification. Accuracy relative to 1526 display: ±1 digit.
Digital Display (1544 only): 7-segment neon gas discharge, 3 digits indicating identity of measuring point.
Scanning Modes (controlled by 1544): Single scan, Continuous scan, Remote step triggered.
Power Supply: 100 to 240 V AC, 50 to 400 Hz.
Power Consumption: 1544: 10 W plus 1545s; 1545: 2 W (from 1544).
Operating Temperature: +5°C to +40°C.
Humidity Range: 0 to 90% relative humidity.
Dimensions (A cabinet): Height: 133 mm (5.25 in), Width: 430 mm (16.9 in), Depth: 200 mm (7.9 in).
Weight: 1544: 6.5 kg (14.3 lb); 1545: 4.5 kg (10 lb).

Usage Features

Direct Reading and Ease of Operation: The 1526 provides instant, direct digital readings of strain levels in microstrain units, making it user-friendly.

Multipoint Measurement: The system allows for monitoring of up to 5 points on the 1526 alone, and up to 400 points when integrated with the 1544 and 1545 selectors. Each measuring point has individual balance and bridge mode controls.

Digital Display Functions: The digital display can show strain, gauge factor, or the initial balance potentiometer position, which is useful for referencing initial conditions in tests where unloading is not possible.

C-Balance Elimination: The operating principle of the 1526 eliminates the need for C-balance, simplifying setup.

Low Heating Effect: The 0.3 V excitation voltage minimizes heating of strain gauges, making it suitable for testing materials with low thermal conductivity.

Low Pass Filters: Built-in 3 Hz, 30 Hz, and 300 Hz low-pass filters help separate static and dynamic strains and suppress spurious signals.

Hold Function: A "Hold Max." function captures the largest peak strain (positive or negative) for non-repeating phenomena. This is particularly useful for dynamic measurements where both static and dynamic strains are present.

Overload Indication: The digital display flashes to indicate overload conditions, which can be caused by excessive signal, capacitive unbalance, or superimposed hum.

Outputs for External Equipment:

Digital Output (BCD): For data transfer to the 1544 or other digital equipment.
Output 1 (Analog): With adjustable gain and offset, suitable for level recorders (e.g., B&K Type 2305, 2306, 2307) or ordinary voltmeters. Includes a calibration signal.
Output 2 (Analog): For oscilloscopes, providing ±10 V for the full display range.

Multipoint Selector and Control Type 1544:

Logic Control: Manages systems with up to 400 measuring points.
Scanning Modes: Continuous scan, single scan, and remote step scanning.
Point Identity Display: Digital display shows the identity number of the currently sampled measuring point.
Selective Scanning: Ability to ignore individual points in the scanning sequence.
Step Intervals: Selectable dwell times from 0.1 s to 10 s.
B&K Data Bus Interface: Built-in interface for digital data transfer to computers, tape punches, teletypewriters, or printers.

Multipoint Selector Type 1545:

Expandability: Up to 39 units can be connected to a 1544 to expand the system's capacity.
Decade Identification: A decade identification number can be set to determine its place in the scan sequence. Setting it to "00" bypasses the entire decade.

Accessories:

Quarter-Bridge Adaptor ZR 0014: Allows measurements with a single strain gauge (120 Ω dummy gauge included). A ZR 0018 adaptor is available for 350 Ω gauges.
Calibration Bridge ZR 0013: High-precision resistors for calibrating the display to a known strain value (e.g., 2000 µε for a gauge factor of 2.00).

Maintenance Features

Fuse and Voltage Selector: The rear panel of the 1526 and 1544 includes a fuse holder and voltage selector, allowing adjustment for different mains supply voltages (100-240 V AC) and corresponding fuse replacement.

Ground Connections: The 1526 offers internal ground connection options to minimize noise and ground loops, with clear instructions for selecting the appropriate grounding point (mains supply ground or chassis ground via a measuring point terminal).

Cable Preparation and Connection: Detailed instructions are provided for preparing and connecting cables, including recommendations for conductor cross-section area, twisting leads, and shielding to ensure optimal signal integrity and reduce interference.

Connector Assembly: For the 26-conductor cable AQ 0115 and JJ 2604 connectors used with the multipoint selectors, a step-by-step guide is given for assembling the connectors onto the cable, ensuring proper orientation and secure attachment.

Fine Adjustment of Digital Voltmeter: A procedure is outlined for fine-tuning the digital display circuit of the 1526 to ensure perfect agreement between the displayed value and the actual measurement, especially when using the Calibration Bridge.

Troubleshooting Overload: The manual provides guidance on identifying the cause of analogue overload (superimposed signals or capacitive unbalance) and suggests remedies such as selecting a higher bridge excitation voltage, screening leads, or adding a capacitor.