EIA lists about 200 preferred devices, but only a couple of dozen are readily available. Not all types are commercially available (there would be a very limited market for a C0N device for instance).

The 'EIA Class 1 Capacitor Codes' table below shows the Class 1 EIA naming convention. As can be seen from the table below, the tolerance is usually specified for only the 25-85☌ range, but the ☓0 ppm C0G tolerance is sometimes specified to 125☌, and this would be a preferred part for downhole applications (200☌ parts are available from a few manufacturers and rarely ☑0 ppm tolerance parts are seen, but these extremes are not usually necessary and are of course expensive). Size becomes an issue in higher value C0G ceramic capacitors, and in fact it is difficult to find C0G ceramics above about. For lower values (.01 uF and below) the use of C0G capacitors in critical downhole applications is a no-brainer as long as other considerations like voltage rating does not select against them. In general, the lower the class number, the better the overall characteristics, but the larger the size for a given capacitance value.Ĭlass 1 ceramic capacitors include the C0G types (also called NP0 from the old military 'negative positive zero' standard, but said obsolete term is disdained by EIA purists), and various temperature compensating types. The Electronic Industries Association (EIA) classifies ceramic capacitors into four groups (Classes 1-4), and into types within the classes. Surface mount ceramic chip capacitors are becoming more common in the present generation of logging equipment, but leaded ceramic capacitors are still seen. spec CK (BX) style molded ceramic capacitors becoming common in tools built in the 1970's and 1980s during that boom cycle in the oil patch. The old familiar ceramic disc capacitors were ubiquitous historically, with the mil. Ceramic capacitors have found extensive use in well logging tools and surface electronics.

Surface mount capacitor code chart