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Category: Lab Talk

Sanpla Dry Keeper Desiccator Repair

Sanpla Dry Keeper Desiccator Repair

The Sanpla Dry Keeper Automatic Desiccator uses a granular desiccant to dehumidify the inside of the cabinet to about 30-40 % RH. The desiccant is held in a basket equipped with  a heater for regeneration when saturation is reached. The instrument goes through a 30 min regeneration phase followed by about 4-5 hours of moisture removal. This cycle is controlled by a mechanical switch driven by an AC synchronous motor. The instrument in our lab didn’t work any more, meaning…

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Lowering the Temperature of Liquid Nitrogen

Lowering the Temperature of Liquid Nitrogen

  Liquid nitrogen (LN) is widely used in experiments where cryogenic temperatures are needed. The temperature of LN at 1 atm is 77.3 K. Some experiments might require temperatures slightly below this limit. In the phase diagram we are on the equilibrium line between the liquid and the gaseous phase. To push this equilibrium to lower temperatures, toward the triple point we need to lower the pressure. The equilibrium temperature at the triple point is 63.1 K. One way of…

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A Simple Homopolar Motor

A Simple Homopolar Motor

For an annual outreach event at my institution I’m putting together a few easy experiments around electromagnetism. The program for high school students is aimed at getting them interested in STEM. Searching the internet I found a beautifully simple example of an homopolar motor. All that is needed is: A AA battery A few disk shaped Neodymium magnets, slighty larger diameter than the battery Bare copper wire (I used 14 AWG) The battery sits on the stacked magnets. The wire…

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New Purpose for Casting Tape

New Purpose for Casting Tape

I’d like to talk about something I came across a few weeks ago. Due to an accident leading to a broken wrist the ingenuity of glass fiber casting tape came to my attention. Never having had the need for a cast, the technical development in this field passed by me. Googling yielded the product in question: 3M ScotchCast Plus Casting Tape. You briefly soak it in water; then it becomes sticky, while still soft and pliable. Within minutes it hardens…

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