home built surface charge measurement? - Page 1
Forum section: electronics / projects

author: SArepairman
author_rank: Frequent Contributor
timestamp: April 12, 2014, 01:32:45 am
content: is there any way to make a cheap surface charge measurement probe relatively easily?what goes into it? Like the one that dave jones uses to measure his ESD mats and various plastics.the only thing that comes to mind is connecting wires to one of those gold-leaf electrostatic meters used in elementary school demonstrationsmy electrometer only goes up to 100V.

author: miguelvp
author_rank: Super Contributor
timestamp: April 12, 2014, 09:45:33 pm
content: well, you can do it like you said laughingly, wire, aluminum foil.Or do an "electronic" one:http://amasci.com/emotor/chargdet.htmlthere are more elaborate ones:http://www.edn.com/design/analog/4417628/Detect-charged-bodies-with-electronic-electroscopejust google "diy electronic electroscope"Maybe you can put a digital readout instead of the simple LED.

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: April 12, 2014, 10:27:35 pm
content: Some what related , I have had some antenna analyzers get damaged by static electricity .And wandered about a static detector & also would like to see it measure the voltage / current levels ?I figured the issue would be the transient nature of static ?Have to take a longer look at the links .Also any suggestions , is there equipment already out there ?

author: Marco
author_rank: Super Contributor
timestamp: April 12, 2014, 10:52:07 pm
content: The most fundamental part of a surface charge meter seems the vibrating kelvin probe.

author: SArepairman
author_rank: Frequent Contributor
timestamp: April 12, 2014, 11:38:12 pm
content: Quote from: KD0CAC John on April 12, 2014, 10:27:35 pmwell, keithley defiantly sells equipment for measuring electrostatic charge (even as an electrometer attachment) , and you can defiantly buy stuff, but I don't need it that bad, I just wanted a rough idea of what things were at around here.

author: wbeaty
author_rank: Contributor
timestamp: April 12, 2014, 11:52:47 pm
content: I have a nice portable "Field-mill gun" for detecting small e-fields on the order of few-cm surface area. Not good for very tiny charged regions. By IDB in UK (Bangor, Wales.)Look up DIY field mill. It's a non-contact probe. Touching metal to your charged surface will *generate* surface-charges! A field-mill is basically a metal plate with a grounded 2-blade fan whirling in front of it, metal plate connected to a high-Z op amp input. Or just connect the static plate to your scope input and measure the AC peak. As long as the distance to the charged surface is << plate diameter, the peak AC volts is directly proportional to the net surface charge.A much smaller version would be a metal probe vibrated by a loudspeaker, i.e. the old "wobbulator" capacitor from the early days of FM modulators.Or, with extreme DC input impedance FET amps, you can eliminate the rotor/vibrator stuff and just hold the metal probe-plate up to your charged object. If the gigohm/picofarad RC decay time through the amp input is on the order of tens of seconds, then just briefly ground the floating probe-plate while it's far from the charged object, then bring it near for a measurement.Such devices are common on eBay for under $100. Search for "electrostatic locator" or just "electrostatic." The old Simco models are very Ghostbusters-looking. Plus, the input attenuator ahead of the probe plate is a metal *camera iris.*