Abstract: A test fixture of the type that requires repeated manual lifting of weights in a drop-tube for performing an ASTM drop weight test, is provided with a computer automated pneumatically powered lift mechanism. The lift mechanism for the weights responds to a series of computer generated signals that are applied to a set of electropneumatic actuators for driving pistons to lift and drop the weight. Associated with the lift mechanism is a set opto-interrupter devices that generate a position signal representative of the position of the weight to be dropped as it ascends in the drop tube. In use the computer is provided with a desired drop height and essentially continuously compares the position signal with the desired drop height and releases the weight in the drop tube to impact a sample material when the position signal equals the desired drop height.

Abstract: A crystal, which is mounted in a rotatable support for use in tuning the wavelength of an optical parametric oscillator, is maintained at a desired temperature by positioning a heating sleeve to thermally coupled to the crystal and its support in such a way that the crystal is still free to rotate. The heating sleeve has an embedded heating element for connecting to an electronic controller whose dynamic output response matches the dynamic temperature characteristics of the combination of components including the crystal, it rotatable holder and the heating sleeve, so as to quickly stabilize changes in the crystal temperature with a minimum amount of overshoot.