330 Megohm Resistors

[Andy M0FYA]

In a recent 'job lot' purchase recently is a bag of twenty or thirty 330 Megohm resistors, made by Welwyn. Nothing exotic, just little brick-red jobbies, maybe quarter inch in diameter and five-eighths long. The only way I could check a couple was on my insulation tester!

What on earth could these be used for? I can't think of anything. If anyone needs some let me know!

Andy

[pwdrive]

The Heathkit high voltage probe uses a 1090 megohm resistor, as to the original use of the ones you have I can't say but clearly they were available, maybe a high voltage probe or in connection with some CRT circuitry or anti static build up on exposed metal work etc.

Lawrence.

[dennishoy]

We used those and higher values in FET op-amp designs a few years ago for circuits designed to measure the resistance of distilled water using a glass electrode. Unfortunately, they tend to reduce in value when handled without gloves due to sweat and other conducting salts in perspiration.

We went over ot better quality units which were each sealed in a glass tube bit like the reed switch from a relay. At least these could be wiped clean with solvent if handled.