GENERAL DESCRIPTION

The miniature strain gauge amplifier AMP- M10K-B has been developed based on modern chip technology to meet the grow-ing need for strain measurements in very demanding environments, where low noise, miniature size and easy set-up are essential. The design concept is based upon the ability to place a complete strain gauge conditioning (stable 5V-bridge excitation and precision instrumentation amplifier circuitry) in close proximity to the strain gauges. An amplified (high level) output signal which has good immunity to noise can be safely transmitted via slip rings or long cables, which considerably reduces noise and increases signal integrity. AMP-M10K-B is a fixed gain device with nominal gain of 1000. Other fixed gain values are available on request. All the electronic components integrated on board of AMP-M10KB, provide a high bandwidth (7 kHz at Gain = l000), very small overall dimensions and modest power supply requirements (a single 9V battery or unregulated power supply 8-16V), which makes it an ideal tool for field instrumentation engineers.

Applications of the AMP-M10K-B include:

• automotive

• rail traction

• aeronautics

• rotating machinery

• specialised load-cells

• civil engineering

• biomechanics

• research & development

OPERATION

For normal operation, AMP-M10KB re-quires single voltage supply between 6V and 16V DC. Most typically the unit is powered by a 9V or 12V battery, or a DC power supply. To handle both positive and negative output signals, the unit is equipped with on-board negative power supply rail generation electronics which eliminates need for dual power supplies. This feature considerably increases flexi-bility in field instrumentation applications. The AMP-M10KB can also be used as a front end of microprocessor based data acquisition systems, by simply adjusting the initial out-of-balance to the required positive reference (typically 2.5V). Current consumption of AMP-M10K-B is very low (less than 4mA) and hence the required current capacity is determined by the strain gauge resistance (46 mA with

120Ω and 18 mA with 350Ω strain gauges). Typical connection to the strain gauge bridge is shown in Figure below.

AMP-M10KB

MINIATURE STRAIN GAUGE

AMPLIFIER

To visually check if the unit is powered, AMP-M10KB is equipped with red LED po-sitioned above the 5V-bridge supply pin. If correct power supply conditions exist the LED goes on. This feature can be particu-larly useful in cases when the strain gauge installation and AMP-M10KB are positioned in remote location from power supply sources and quick visual inspection can easily identify problems with power supply. BALANCING

AMP-M10K-B is equipped with a 25 turns on-board balancing potentiometer which al-lows to zero the output for ZERO load con-ditions, or to pre-set the required reference voltage. For special applications, where ad-justment of bridge out-of-balance is not re-quired, the unit is also available with no bal-ancing or calibration facility. ELECTRICAL - MECHANICAL

The device is screened to protect against EMI and is totally encapsulated to provide an extremely ruggedized package with guaranteed operation up to 3 000 G.

AMP-M10K-B is a SIL device based on standard 0.1" pin spacing, which also make it convenient for direct applications on the standard SIL sockets.

Both input pins IN+ and IN- are internally protected against voltage transients of up to +/-40 V by using an internal current limiting device and not series resistors which could contribute to input noise. The inputs are protected even if the power supply is dis-connected or turned off. The device is also protected against continuous output short circuit to ground. SPECIFICATION

Dimensions: 30 x 21 x 10 mm Power supply: Single 7 - 16 V Bridge supply: constant 5V nom. Gain: Fixed 1000 Dynamic response: DC - 7 kHz (-3dB) Temperature range: -40 oC to +85 oC (extended range available) Weight: 10 G Nonlinearity: +/- 0.02 % of FSR CMR: 100 dB (min) Gain vs. temperature: +/-25 ppm/oC typ.

OPTIONS: 1. AMP-M10K (no balancing) 2. AMP-M10KB - amplifier with on-board balancing facility