Introduction

The GAGE-3000 is a high quality interface board, used for interfacing any bridge-type type transducer such as Strain Gages, Pressure Sensors and other bridge-type transducers, as well as voltage producing devices such as Piezo Sensors, Temperature Sensors, Photo Diodes and EEG/ECG inputs.

The GAGE-3000 provides a variable excitation, capable of driving up to 80 mA, at voltage range of 1V to 20V. The excitation voltage is symmetrical about ground level, so that the common mode voltage is approx. 0V. For example: an excitation voltage of 12V will be ±6V relative to ground.

The GAGE-3000 can be configured as a single board for one transducer or up to six transducers on a single board.

The GAGE-3000 also contains an Instrumentation Amplifier, with a variable gain of 200-1500, and a variable offset control. The output of the Instrumentation Amplifier is fed to a double pole Low-Pass-Filter, then passed via a driver buffer to the output port. The cut-off frequency of the Low-Pass-Filter may be changed by replacing two capacitors, CX1 and CX2, with capacitors of other values. The following Table provides capacitors values for some often used cut-off frequencies:

The GAGE-3000 also has a bridge loading resistor Rx, connected in series with a variable trimpot (variable resistor) designated P2. The resistor is used for correcting the offset of a bridge, which has a high offset level that cannot be corrected by using the on-board offset control. This resistor has to be defined and connected by the user. Please note that this resistor may affect the linearity of the sensor, therefore it is recommended to correct the high offset by fixing the transducer.

The excitation of the GAGE-3000 may be changed by using a trimpot designated P6, while the excitation level may be measured between the -EXC and +EXC test points. The gain is adjusted using P1.

The GAGE-3000 requires an external stabilized power supply of ±8V to ±15V. We offer an optional battery power supply that works from a 12V battery.

Figure I Block Diagram:

Features:

1. For use with any bridge-type transducers, pressure gages, strain gages, etc.

2. High gain - 1500 standard,up to 20000 optional

3. Ultra high input impedance - 1 GW

4. High frequency response - up to 120kHz

5. Built-in user-programmable Low Pass Filter

6. Built-in excitation

7. High common-mode rejection - 115dB min

8. Low noise, low offset and drift

9. Low cost

Applications:

1. Weighing systems

2. Interfacing of load cells to A/D cards

3. Amplification of low-level sensors (Pressure Transducers, Light-sensing Devices, Thermistors, etc.)

4. Medical applications: EEG, ECG, etc

Technical Specifications:

PARAMETER

VALUE

Gain

100-1500 (adjustable by user) up to 10,000-by request

Gain Non-Linearity

± 0.002%

Gain Temp. Coef.

5 ppm/C°

Input Offset Drift

1 µV/C°

Output Offset Drift

25 µV/C°

Input Offset Vs. Supply

85 dB

Input Impedance

1G

Drift. Capacitance

5 pF

CMRR ( DC - 100 Hz )

100 dB

Bandwidth ( Gain 100 - 1000 )

20 kHz min. (-3 dB)

Setting time to 0.01%

80 µ Sec.

Input Noise Voltage (@ 1 kHz)

5 nV/

Output Noise

100 nV/

Supply Voltage Range

±8V to ±15V

Excitation Level

±1V to ±10V

Excitation Current (max.)

80 mA

Excitation Drift

15 ppm/C° ±10 µV/C°

Excitation Noise (DC - 100 kHz)

0.6 mV max (@300R load)

Excitation Noise (DC - 1 kHz)

0.2 mV max (@300R load)

Operating Temperature

0 - 70 C°

Bridge Resistance Range

50 - 20,000