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PTI Muscle Strip Measurement Accessory

 

CONTENTS

1

Introduction

2

DC Bridge Amplifier

3

Preparation for Measurement

4

Service

 

 

 

Introduction

The module has been developed to facilitate the simultaneous measurement of contractile force and intracellular fluorescence changes associated with ion transients. The module consists of a muscle strip adapter, a tranducer assembly and a DC bridge amplifier.

The amplifier supplies the signal generated by the transducer to the PTI computer interface and is compatible with the FeliX™ software.

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DC Bridge Amplifier

The universal DC bridge amplifier (SGM) receives signals from the FSG-01 displacement transducer, amplifies the transformed signals, and can be connected to an appropriate direct-writing recorder or to a computer interface. When used with a PTI system, the output is connected to one of the analog channel BNC inputs A1 through A6.

The FSG-01 transducer family has been developed for in-vitro isolated organ measurements, and comprises transducers with the following weight limits:

10 gr
50 gr
100 gr
300 gr
1000 gr

Both horizontal and vertical displacement versions are available.

The bridge amplifier accepts any kind of force/displacement, and acceleration input signal from transducers that have half or complete Wheatstone bridge design.

It automatically recognizes if we use complete or a half bridge transducer when the input cable is connected.

Technical Parameters

Bridge supply voltage 1-7 V, gradual internal adjustment in 1 V steps
Standard adjustment 2 V or 5 V
Gain 100,000-fold continuous through a potentiometer
Offset 10-turn trimmer potentiometer adjusts the balance of the bridge
Analog indicators 2 LED’s provide bridge balance and visual information during the measurement of the +/- voltage range
Low pass filter Three-positions of FILTER with values of 3, 10, 40Hz
Input parameter Eliminating half of the bridge, it is 1 Mohm symmetrical
Output parameter Output is 0-5 V continuously adjustable
Power supply +/-20 V, 250 mA standard power supply bus
Weight 0.5 kg

 

Amplifier Installation

If not delivered in a rack, the coupler module must be slid into an R-01 rack on the plastic guide rails. Upon coupling with the rear it will automatically receive the necessary supply voltage. Secure the coupler in the rack with the two knurled-head screws.

The input/output and the computer connectors can be found at the back of the coupler.

The red banana jacks are the output terminals, the white banana jack is the signal ground.

These may be replaced by a BNC connector in later units. The 9-pin Canon terminal (SENSOR) serves to couple the transducer head.

The black grounding banana jack on the back of the R-01 rack serves to provide common ground to the rack and the instrument together.

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Preparation for Measurement

After installation of the module, connect the power cable to the AC supply.

The input cable (9-pin Canon) must be connected to the socket with the SENSOR inscription. The cable with the red and white banana plugs connect to the red and white banana jacks respectively, and the BNC end connects to one of the analog inputs of the computer interface. The icon for the same analog input has to be connected to a "black box" icon in the configuration setup of the FeliX software to enable acquisition of the signals.

After the preliminary operations as above, we begin by adjusting the controls on the front panel:

  • Place the MEAS/GND switch in the GND position.
  • Place the FILTER switch in the 40 position.
  • Turn the 10-turn potentiometer labeled OFFSET to a value of 5.00.
  • Turn the GAIN knob completely clockwise.
  • Turn the POWER switch ON. The switch will light up to indicate that the unit is under power.
  • The transducer (FSG-01 or FSG-02) must be connected to the input cable, so that the black marker points are aligned opposite each other.
  • Flip the MEAS/GND switch to MEAS. Adjust the desired signal level in the absence of any tension on the transducer with the OFFSET dial.

At this point the analog signal in the FeliX software may be calibrated by putting known weights of 1,2,3, etc., grams on the transducer hook and registering the corresponding analog voltage values. These can subsequently serve to build a LUT (look-up-table) or standard calibration curve.

In order to start your first experiment, try the following protocol as a first approximation to get acquainted with the muscle strip measurement system.

Use of the muscle measurement system

  • Stop the peristaltic pump.
  • Remove the adapter release.
  • Loosen the thumbscrew and rotate the transducer assembly sideways out of the way.
  • Remove the muscle strip holder assembly from the cuvette.
  • Attach the muscle strip to the lower muscle hook. The excitation beam will impinge on the sample about 5-8 mm from the base of the hook. The surgical thread attached to the other end of the muscle strip will be lead through the top of the adapter assembly and subsequently looped around the upper muscle hook on the transducer.
  • Insert the muscle strip adapter assembly into the cuvette. When positioned correctly, the register pin will fit the hole in the adapter plate. Secure the adapter with the adapter release.
  • Start perfusion with the peristaltic pump.
  • Rotate the transducer back to its original position and lock it by tightening the thumbscrew.
  • Hook the surgical thread to the upper muscle hook on the transducer and establish the desired pretension using the micrometer adjustment thumbscrew.
  • With the muscle strip in place, use the micrometer adjustment thumbscrew to establish a tension that will serve as the resting level, and, using the OFFSET dial, adjust the transducer signal to give a deflection of the desired level (say, 2 V). Over time, the voltage signal will drop as the muscle strip stretches. You may wait until it reaches an equilibrium or apply a little more tension to bring the signal level up to the desired value for the initial resting level.

 

Upon eliciting muscle strip contractions, the deflection of the analog voltage corresponds to changes in the force that is applied to the transducer and can be calibrated with a LUT constructed by applying a series of weights to the transducer after the measurement is completed.

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Service

All service should be performed by PTI personnel.

If the transducer is changed, the coupler must be re-calibrated as follows:

  • Connect the transducer to be calibrated.
  • Flip the MEAS/GND switch to GND, the GAIN knob fully clockwise.
  • Set the ZERO position of your calibrating instrument (analog screen).
  • Flip the MEAS/GND switch to MEAS.
  • Turn the "OFFSET" dial to 5.00.
  • Set the output to zero by adjusting the LOW trimmer potentiometer.
  • Load the transducer with the smallest weight corresponding to its parameter scale (1 gram in the case of the 50 gr tranducer).
  • Adjust 5V on the calibrating instrument with the help of the HIGH trimmer.

Adjustment of the supply voltage of the transducer:

  • The voltage can be adjusted using the jumpers on the board.

The supply voltage for the given transducer is determined by the parameters indicated in the catalogue of the transducers:

  • The recommended value for the FSG-01 is 5V.

Our couplers are delivered factory-adjusted as above.

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