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Article 3: Problem with scratchy thermal pens
In the past, Lafayette Instrument fielded calls from examiners who were experiencing problems with pen scratching. The difficulty develops primarily in the older design of X Series and older, electrocardio and (some) GSR pens. The problem can stem from two causes; (1) a maladjusted pen clip and or (2) a bent pen tip. This article will deal primarily with solution to the first problem.
(1) The pen clip should be bent so it rests directly over the center of the pen point, (see illustrations below) thereby not putting extreme tension on the pen itself. The purpose is to keep the pen in the cradle while at the same time allowing It to swivel up and down, maintaining constant tension at the point where the pen tip meets the paper. The spring design found on the amplifiers mentioned above was chrome-plated and not very flexible this, therefore, gives it the tendency to break rather easily. If when adjusting the pen clip, it does break; please contact Lafayette Instruments and ask that they supply you with a pen cradle (Model 76310) which has a new zinc plated clip which is more flexible and resilient.
(2) The second problem is a relatively easy one to correct. If you notice that a pen tip has become bent and does not rest flat on the writing surface, using your fingertips gently reshape the pen so that It again looks straight when examining it from both front and side.
This article was extracted from Lafayette Instrument Co. Newsletter "Polygraph Update" Vol., Number & Date unknown