THORLABS AMP002 Strain Gauge Pre Amp User Manual

THORLABS AMP002 Strain Gauge Pre Amp

Overview

This pre-amplification circuitry is designed to amplify resistance changes within a full Wheatstone bridge strain gauge, to produce a signal suitable for monitoring and interpretation by the Thorlabs strain gauge reader or other piezo electronics with feedback. This circuit can also be used in other custom applications. The amplification circuitry uses a low power, general purpose instrumentation amplifier offering excellent accuracy suitable for strain gauge bridge amplification. Current-feedback input circuitry provides wide bandwidth even at high gain (200kHz at G = 100). A single external resistor sets any gain from 1 to 10,000. The INA128 amplifier component provides an industry standard gain equation. Under normal operating conditions the Thorlabs strain gauge reader anticipates a voltage range of >0v to 2V Pk-Pk for minimum and maximum strain.

Note : There is no phase monitoring to determine bridge polarity. The bridge should only be used for positive strain, where the bridge does not cross the balance point during operation.

Safety

Safety Information
For the continuing safety of the operators of this equipment, and the protection of the equipment itself, the operator should take note of the Warnings, Cautions and Notes throughout this handbook and, where visible, on the product itself. The following safety symbols may be used throughout the handbook and on the equipment itself. The following safety symbols may be used throughout the handbook and on the equipment itself.

Warning: Risk of Electrical Shock
Given when there is a risk of injury from electrical shock.

Warning
Given when there is a risk of injury to users.

Caution
Given when there is a risk of damage to the product.

Note
Clarification of an instruction or additional information.

Adjustments

1. To obtain the required voltage range the offset (VR2) and gain (VR1) potentiometers may need to be adjusted. See the circuit diagram opposite.
2. For some applications the default gain range may need changing beyond the limit of the adjustable gain. In this instance the value of R3 may need to be changed. The following equation can be used to help determine what gain resistance is needed.

Note
In order to avoid saturating the Thorlabs strain gauge reader (or other piezo electronics feedback), under full strain conditions the output should not exceed 2V Pk-Pk.

D-Type Connections

1. Pin1 : Oscillator Input
2. Pin2 : +15v Input Supply
3. Pin3 : -15v Input Supply
4. Pin4 : 0v Supply
5. Pin5 : Amplifier Output
6. Pin6 : 0v Supply
7. Pin7 : ID Resistor Connection
8. Pin8 : N/C
9. Pin9 : N/C

Note
The pin out of the D-Type connector is such that the amplifier can be connected directly to the Thorlabs range of closed loop controllers. If used with the BPC301 or BPC302 seriescontrollers, the output is limited to 75 V. If the full 150 V drive is required the BPC303 controller or KPZ101 Piezo K-Cube together with the K-Cube strain gauge reader (KSG101) should be used. These controllers provide all the circuitry to convert the output of the preamplifier to a measure of displacement, allowing accurate position monitoring. In addition, the preamplifier can also be incorporated into other equipment

Strain Gauge Bridge Connections

Caution
When used with the BPC series controllers, connections to the bridge amplifier circuit are as detailed in Fig. 1.1 above. When used with the KSG101 K-Cube Reader, the TP2 and TP3 connections must be swapped as follows:

1. TP1 (Red) Oscillator output to strain gauge bridge
2. TP2 (Blue) Positive input for differential amplifier
3. TP3 (Yellow) Negative input for differential amplifier
4. TP4 (Black) Ground

Caution
For correct operation, the value of the ID resistor (R6) must be chosen to match the travel of the piezo stack being driven – see Table 1 in Fig. 1.1 above. Use a standard 1% 0.25W resistor

The Thorlabs piezo actuator with feedback (PZS001) is fitted with a full Wheatstone bridge strain gauge that can be monitored by this circuitry

Thorlabs Worldwide Contacts

For technical support or sales inquiries, please visit us at www.thorlabs.com/contact for our most up- to-date contact information.

USA, Canada, and South America Thorlabs, Inc.
sales@thorlabs.com
techsupport@thorlabs.com

**DISPOSAL

**

Thorlabs verifies our compliance with the WEEE (Waste Electrical and Electronic Equipment) directive of the European Community and the corresponding national laws. Accordingly, all end users in the EC may return “end of life” Annex I category electrical and electronic equipment sold after August 13, 2005 to Thorlabs, without incurring disposal charges. Eligible units are marked with the crossed out “wheelie bin” logo (see right), were sold to and are currently owned by a company or institute within the EC, and are not dissembled or contaminated. Contact Thorlabs for more information. Waste treatment is your own responsibility. “End of life” units must be returned to Thorlabs or handed to a company specializing in waste recovery. Do not dispose of the unit in a litter bin or at a public waste disposal site. www.thorlabs.com

References

• Thorlabs, Inc. - Your Source for Fiber Optics, Laser Diodes, Optical Instrumentation and Polarization Measurement & Control
• Thorlabs, Inc. - Your Source for Fiber Optics, Laser Diodes, Optical Instrumentation and Polarization Measurement & Control
• Thorlabs, Inc. - Your Source for Fiber Optics, Laser Diodes, Optical Instrumentation and Polarization Measurement & Control

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