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But I first did a quick test and applied power long enough to confirm that it started to spin smooth as silk. For more on straw bag tote visit the web-page. This provides both a load to test the filament power supply as well as a warmup delay (due to its filament heating) to test the interlock circuits of the ion gauge controller. The long (but normal) warmup time is the most significant annoyance with the 227A. Cycling between 1 atm and high vacuum doesn't result in much of a change in the zero setting - perhaps 1 or 2 microns at most. Now, it can be zeroed at any time but the zero setting drifts by about 30 microns from a cold start to an hour or so later. After an hour or so, it passed 150 microns. So, I haven't decided whether to use the 4-1/2 digit panel meter (with BCD output) I also found in the trash as the readout for this gauge. As noted, most ionization gauge controllers use resistance or joule heating for degas. Veeco also produced controllers using joule heating degas - the RG-830 (and RG-83).


The most common and somewhat standardized variety are of the "Bayard-Alpert" design using a hot filament (as in a vacuum tube). Handcrafted on the island of Madagascar, this sisal tote is constructed using sustainable materials. These materials include fibers such as rattan, bamboo, and coconut, as well as natural dyes and other sustainable materials. The actual voltages found on the various pins as well as emission current range will depend on the design of the controller. To the right you will see the cover of my book and two finished pages from the book. Two techniques may be used: Resistance heating (most common): This provides current to heat the grid electrode directly and the collector by radiant heat. How to Make Bead and Wire Hearts Mixed techniques including wire work, beadwork and polymer clay are used. Beach bag: Large straw bags are spacious enough to carry all your essentials like a towel, sunscreen, and a good book.


WARNING: Unlike thermocouple gauges with their mostly low voltages, ionization gauges may have 150 V to 800 V or more with enough current available to be lethal inside the unit as well as on the various electrodes of the ion gauge tube sensor. Inputs from other (e.g., TC vacuum gauges) may also be used for this. However, cold cathode ion gauges are also available. There are many types available. 30 VDC. Since this only has to source current, it may just be a zener circuit and will only show a voltage when there is an actual current flow. Electron bombardment degas should not be operated above about 10-4 Torr as the effect will be of a glow discharge rather than direct electron flow reducing effectiveness and possibly damaging the grid and collector by oxidation. Unfortunately, the basic design of this system results in the output for zero microns being derived from the difference of two large numbers so small changes in either have a large effect. However, ion gauge controllers are readily available surplus for a small fraction of their new cost. The layers are often repeated which is why it is oftentimes called an Italian Trifle. This current goes into a high sensitivity amplifier called an "electrometer" which drives an analog meter or digital display.


However, I did find a problem and with an improvised but effective repair it now goes down to about 3 microns after flushing and an oil change. And the base pressure is now below 25 microns. Pressure cannot be measured while this type of degas is in progress. The only ones I've seen with electron bombardment degas are a couple of old Veeco models - the RG-840 (and RG-84 which is basically the same). These are darn small changes but when their sum is multiplied by the gain of the output stage (about 15), would appear to account for the zero drift. The only part which is non-trivial is the electrometer amplifier which must deal with extremely small values of ion current. Thus, for a full scale reading of 10-7 Torr, the amplifier must have a full scale sensitivity of 1 nA! Electrometer amplifier: This is a high sensitivity amplifier range selectable between 10-3 and 10-7 Torr full scale (give or take a an decade or two). A compressed "log" scale may be selected on some models which compresses the entire range into a single meter display. I have checked the 227A's calibration against my Hastings VT-4B thermocouple vacuum gauge and once zeroed, the readings do track within 20 percent over its entire range of 0 to 1 Torr.