new life to a MEGGER from 1970, great score - Page 1
Forum section: electronics / projects

author: oz2cpu
author_rank: Frequent Contributor
timestamp: September 23, 2022, 10:31:28 am
content: i always wanted a megger, to perform 1kV isolation safety tests on mains stuffbefore applying power, but had a little bit too much glue-in-the-pocketto go out and purchase a new one. seen the prises lately ?? they are crasy..scored a super old one, for cheaps, and fixed itthat was a lot of fun,https://youtu.be/0wHV_bP1DVc

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 23, 2022, 10:59:49 am
content: Quote from: oz2cpu on September 23, 2022, 10:31:28 amyeah crazy cheap...ANENG MH12 $40if you are personal use. if you can make money out of it, you can choose from more reputable brand such as Sanwa etc or even fromMegger itself in sub $1Kand possibly get back your money in a matter of a day or few days.

author: jonpaul
author_rank: Super Contributor
timestamp: September 23, 2022, 05:33:30 pm
content: This 500V inverter type Megger was €5 at a street sale in ParisFrom UK or Germany, still currently sold £ 650..799!has 0..50 ohm earth resistance scale and 100k..50 M Ohm 500V scale.uses 6 x AA batteryJon

author: strawberry
author_rank: Super Contributor
timestamp: September 23, 2022, 06:57:21 pm
content: cheap isolation tester

author: trobbins
author_rank: Frequent Contributor
timestamp: September 23, 2022, 10:14:22 pm
content: I'd comment that even diy use of an insulation resistance tester for mains circuitry needs a range that extends to at least 1,000 to 2,000 Megohm, and there can be benefit in going higher for those interested in leakage. 20 or 50 Megohm may be the official demarcation in some mains safety standards, but if there is leakage to that level then there is a duty of care to know why. There can be many practical other uses for a megger and I would put it to the top of a 'must have' list for a competent bench. So although the restoration of some vintage equipment is enjoyable, that shouldn't per se negate the need for better equipment to normally be used when safety is at risk.

author: jonpaul
author_rank: Super Contributor
timestamp: September 24, 2022, 08:45:10 pm
content: Rebonjoure,We worked in HV and SMPS, also magnetics for decades.A moment to clear up:A "Hypot" tester (TM) is designed to check the leakage current (DC or AC) that flows between the DUT eg L1 or L2 to earth or neutral.They use a variable AC or DC source, and current meter available in wide range of test V eg 2500/5kV>>up to 50 or 100 kV:https://hvinc.com/products/https://www.spselectronic.com/en/products/hipot-1/These can also display the insulation resistance in megohms.Regulatory limits define maximum currents which differ in a 240 vs 120V mains, or for patient attached/non-patient medical, etc.A Megger is a different device:A special analog meter movement connected to a HV generator (hand cranked or inverter) displays the RATIO of V/I = R in megohms, at one or more fixed voltages eg 100/500/1kV.It does not check leakage current.Some include a low R range to check earth safety resistance eg 0.1...50 Ohms.https://www.instrumart.com/assets/Megger-Guide-to-Insulation-Testing.pdfNotice that at HV all insulators are NON LINEAR, so megohms DECREASE as voltage increases and leakage ALWAYS increases when you exceed a certain voltage threshold.Meggers are used in the field to check if a cable has insulation capable for the applied voltage.HyPots are intended for safety testing of products usually in the lab.Finally GenRad and others made HV megohm bridges that could test teraohms at test applied V 50..1k..2kV like the GenRad (IET) 1864https://www.ietlabs.com/genrad-1864-megohmmeter.htmlWe have used all of these types of instruments in our consulting and design work.Hope this note is of interest,Jon