Abstract: The stirring apparatus is an electronic design that generates rotating magnetic fields to drive magnetic stir bars within vials placed above the cover of the stirring apparatus. Below the cover is a magnetics board containing multiple vial groups of four air core coils arranged in rectangular patterns. Each vial group has with two pairs of diagonal coils. The coils in each pair are wired in series and have opposite winding directions. Each pair is driven by a different phase of a stepper motor driver. The vial groups are spaced appropriately for placing one vial above each group. The adjacent coils of adjacent vial groups are driven by the same phase and have the same magnetic direction. The cover contains an array of pole standoffs that matches the coil pattern. The hollow center of each air core coil contains at least a portion of one pole standoff.

Abstract: The stirring apparatus is an electronic design that generates rotating magnetic fields to drive magnetic stir bars within vials placed above the cover of the stirring apparatus. Below the cover is a magnetics board containing multiple vial groups of four air core coils arranged in rectangular patterns. Each vial group has with two pairs of diagonal coils. The coils in each pair are wired in series and have opposite winding directions. Each pair is driven by a different phase of a stepper motor driver. The vial groups are spaced appropriately for placing one vial above each group. The adjacent coils of adjacent vial groups are driven by the same phase and have the same magnetic direction. The cover contains an array of pole standoffs that matches the coil pattern. The hollow center of each air core coil contains at least a portion of one pole standoff.

Abstract: The stirring apparatus is an electronic design that generates rotating magnetic fields to drive magnetic stir bars within vials placed above the cover of the stirring apparatus. Below the cover is a magnetics board containing multiple vial groups of four air core coils arranged in rectangular patterns. Each vial group has with two pairs of diagonal coils. The coils in each pair are wired in series and have opposite winding directions. Each pair is driven by a different phase of a stepper motor driver. The vial groups are spaced appropriately for placing one vial above each group. The adjacent coils of adjacent vial groups are driven by the same phase and have the same magnetic direction. The cover contains an array of pole standoffs that matches the coil pattern. The hollow center of each air core coil contains at least a portion of one pole standoff.

Abstract: The pulse oximeter instrument of the present invention includes switched gain, channel rotation and bootstrap amplification features. In one embodiment, a time-division multiplexed gain circuit is provided in receiver circuitry and is equipped with a switched gain amplifier to faciliate the use of a fixed light source drive and otherwise improve the signal processing characteristics of the instrument. Signal processing is further enhanced via use of a transimpedance amplifier and bootstrap amplifier interconnected across one or more photodiodes. The apparatus time division multiplexes (TDM) the optical input channels to customize the gain response of the apparatus to the variable characteristics of each input channel. Thus, the channel-specific error sources are determined and precisely eliminated from the input data. The channels may also be rotated in subsequent signal conditioning that entails demultiplexing/multiplexing.

Abstract: An improved photoplethysmographic measurement system is disclosed in which a portion of a time division multiplexed (TDM) signal represents an ambient light level, and other TDM signal portions represent detected levels of two or more centered wavelengths of transmitted light. The ambient and detected light portions of the signal are simultaneously applied to the inputs of an instrumentation amplifier(s) so as to produce a continuous output voltage that is proportional to a difference in voltage between the ambient and detected light portions of a TDM signal. Such an approach provides for ambient light level subtraction with reduced noise and componentry.