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Introduction to the FTA188

This document will help you get started with your new FTA188.

The FTA188 uses fixed magnification optics. The magnification is not directly affected by the focal position, as it is with the Telecentric lens type used in FTA125 and FTA135 instruments. This makes setup easier. The horizontal field of view of the lens is approximately 6.4mm.

The FTA188 is a direct-view instrument similar to the FTA200. It also can use FTA200 accessories such as stages and chambers.

FTA188 Contact Angle/Surface Tension Analyzer

Initial Setup

A single cable connects to FTA188 to the computer's frame grabber. The connectors are arranged so they only plug in one way on the FTA188. Make sure you plug the computer end into the FTA supplied frame grabber and not some other function that might have a similar connector on the computer. The camera's power and video connectors are removed for shipment to protect them. They only plug in one way, so there is no uncertainty.

The FTA188 backlight uses a broad-area LED array. It has a separate toggle switch to turn it on and off. This allows the instrument to remain plugged in but have the LED off when not in use.

Syringe and Needle

A Gilmont micrometer type syringe is supplied. It has a 2 milliliter glass burette with a Teflon plunger. It is easily disassembled for cleaning. Standard Luer-hub needles attach to the burette. Needles are available in a wide variety of sizes and materials. A small selection of needles is included with the instrument, but you should ascertain what sizes are appropriate for your work and purchase them separately.

Dispense liquid by rotating the topmost portion of the barrel clockwise. You can retract liquid by turning counter-clockwise.

The syringe drops into the holder and is secured by a thumbscrew on the right-hand side. Use just enough pressure to prevent the syringe body from turning when you twist the barrel to dispense liquid. It is possible to set the thumbscrew so you can remove and replace the syringe without touching the screw, yet have enough friction to keep the syringe body from turning during dispense.

The syringe body is marked so you can tell how much volume the plunger has displaced during a move. The smallest graduations on the scale correspond to 2 microliters, but you can adjust the volume to a fraction of a microliter.

There are two spare syringe holders to the side in case you have multiple syringes.

The syringe rides on a rack-and-pinion Z axis. Adjust this up and down as required. The needle passes through a small beveled hole that acts as a guide. You can adjust the precise position of the needle guide by loosening the two screws at the back of the needle guide piece. This allows you to position the needle in the center of the screen. The hole in the needle guide is large enough for a #20 needle. This is the largest needle you will use in common work. If you need to use a larger needle, you may have to drill out the guide hole a small amount.

Always keep your syringe clean. Washing with methanol, followed by a thorough dry, is sufficient for most test liquids.

Try to prevent air bubbles when you fill the syringe. One way to clear bubbles is to turn the syringe upside down and dispense a small amount. This will push the bubbles up and out.

LED Backlight

The LED backlight uses an array of twenty-four high intensity 660nm red LED's followed by a diffuser. The direction of the light is rotated to horizontal by a 20mm prism. All of this is in the light box mounted at the far right. The light box is fixed with no adjustments. The only control is the on/off toggle switch. The switch is on when up.

Microscope and Camera

The microscope and camera have two adjustments: focus and viewing angle.

Focus is adjusted by moving the microscope closer or further away from the drop using a rack-and-pinion stage. The stage has a lever to lock it in position. This must be off to move the stage. Re-lock the stage after focusing.

The FTA software has a Focus tool which is enabled on the Analysis | Live Analysis tab of the Video form. This will show a profile of gray scales about the cursor: place the cursor over a sharp edge in the image. Adjust the focus for greatest sharpness. The way most people do this is to rock the focus back and forth to determine the best central setting.

The microscope does not have an adjustable aperture or iris. This is not necessary because the depth of field is excellent for the magnification provided.

The viewing angle can be adjusted for contact angle measurements. Small samples are best served by a horizontal angle but large samples require a look-down so the camera looks across the sample and perhaps the sample needs to extend under the microscope and camera. Loosen the fixing screw in the upper left position of the microscope holder plate. Then you can rotate the microscope from horizontal to 7 degrees look-down. Re-fasten the fixing screw after adjustment.

The Contact Angle tab on the Movie form has a place to enter the Camera Angle so contact angle measurements can be corrected for it. The correction is only important for small contact angles (e.g., less than 30 degrees). Interfacial tension measurements should always be made with a horizontal view angle.

Magnification Calibration

Interfacial tension measurements require a very accurate magnification value. Magnification can be calibrated by measuring an object of known size or the interfacial tension of a known liquid (perhaps the easier way).

The FTA188's microscope is calibrated at the factory and is recorded on a form sent with the instrument. This number should be entered on the Calibration tab of the Movie form (take a SnapShot to make this available). Use the Calibration by Directly Setting nm/pixel text box. This calibration should be satisfactory for most work, but obviously if the microscope is disassembled for any reason, a new calibration will be necessary.

Specimen Stage

The specimen stage has rack-and-pinion adjustments on all three axes.

A separate carrier plate is provided for convenient mounting of small specimens. This plate slides on and off the main stage.

The slots in the carrier plate are for absorbent specimens where you want an air interface under the specimen in case it saturates. Paper is an example.

The instrument is designed so that very large samples can slide in from the right hand side. With an optional holder, 300mm (12 inch) wafers can be inspected over their entire surface with the FTA188.