micronta multimeter resistor - Page 1
Forum section: electronics / repair

author: aleeeeaaa
author_rank: Newbie
timestamp: November 30, 2023, 06:12:30 pm
content: I have a Micronta multimeter model 22-204a. There is a burned resistor rated at 0.48 ohms. What can i substitute that resistor with. I don't know what wattage resistor to use. Looking on Mouser and Digikey i noticed it does not list resistors as 0.48 ohms or even 0.50 ohms. Not sure what to order. I need help on this. Thanks, Randy

author: BreakingOhmsLaw
author_rank: Frequent Contributor
timestamp: November 30, 2023, 08:42:36 pm
content: Providing an image or at least the Information whether its SMT or THT or the dimensions would help. That's why you are not getting responses. We're not mind readers, you need to put in put in some effort.Anyway:https://www.digikey.com/short/j8hfvpcnhttps://www.digikey.com/short/8drqn0b9

author: BrokenYugo
author_rank: Super Contributor
timestamp: November 30, 2023, 08:49:50 pm
content: You make odd values with series or parallel combinations of common values e.g. 1+1+12 in parallel comes out to .480. Wattage you need to eyeball it (post pictures, ideally with ruler in frame for scale), find a schematic/parts list that mentions it, or reverse engineer and calculate the dissipation. Guessing this is one of the current shunt resistors?

author: floobydust
author_rank: Super Contributor
timestamp: December 01, 2023, 03:04:51 am
content: Yes I think 0.5Ω with 12Ω in parallel will work, for the 500mA range shunt to get R8 0.48Ω and wattage... at least 1/2W but perhaps higher say 1W to tolerate some overload.Not sure of the original part's rating.edit: The original 1970's resistors are made by KOA and metal film, OP's shunt looks wire-wound though. StandardEIA valuesare 0.47 and 0.481 (but no stock of that could I find).Going to 0.47Ω would be around 2.1% low on 500mA range DC current measurements, others less lower compared to the original 0.48Ω

author: aleeeeaaa
author_rank: Newbie
timestamp: December 01, 2023, 03:45:50 pm
content: Thanks, i'll give it a try. Looking at the circuit board picture you sent, it is the black resistor that burned up. Thanks to all of you for the help. Randy

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: December 01, 2023, 05:07:38 pm
content: .47 Ohm Resistor on ebayhttps://www.ebay.com/itm/144955764019?hash=item21c0096d33:g:TFYAAOSww~Rj9PDR&amdata=enc%3AAQAIAAAA4Iph7JrltgFUYL%2BrJJgf0FUxnX%2BAjV8c2trU8uzsQoAA6f6OytGZ6r6ENaioYjZN3iYBCseD2XdsG20zjgyXwxt3KvLPrjlNpzv71%2FLP7sXLfNK15a8E49uZkdzujIC0tqeJwIdL%2Ft1HbFbFKBY%2FUYQ2d6Mj6OO5eaiMqKeKovUEdxha0mU4vzQrvHYrLcIQHb7L3%2BFDH6LniQpiipWuoOZBWaDMzNy8wD2imPJOlh7sa4oSXB1%2BAQ0hfQb4pJEdCltN%2FeTRgeTgRSUBHoLzA53XP0upm%2BWG6BdXIFwKZnkQ%7Ctkp%3ABk9SR8rQv-OEYw

author: Kleinstein
author_rank: Super Contributor
timestamp: December 01, 2023, 08:51:26 pm
content: Some manganin wire could be an option. I got some from Ebay that performs quite well: TC < 10 ppm/K and essentially no thermal EMF against copper, though a little higher resistance than in the tables.With the 0.2 mm wire this are some 3 cm of wire, so likely better 3-5 parallel strands.https://www.ebay.de/itm/264311798887?hash=item3d8a35fc67:g:FFcAAOSwocli2oM4&amdata=enc%3AAQAIAAAA4K0DtFlArvnUKBFVakL3W%2FvzAi5V8Krwghrl8xQvjy%2FRWOO6%2BFNaQ%2BOK%2By%2BRBa8ySGxhoXB1m0UY5gVJtJ3PaQjLjpczVtgc6pWy2FKgoxQTV4EDOkZoy6SMkwpbpbouuMS9%2FEEMIIW2IgcPpPgbrd6i2NNkNcKOGeFuzijXUSRsT%2B7AoCl4r5004aO%2FXfxoIeFBVZEJ%2Fh%2F2N%2BaE9uuWy0tbaUy1obNWhshKS6zCjd5XEP0LkPo1aQjmI9dPJwiUYvX8QzI7ju0H8HjkJ%2Bk%2FOuVlwo9CZFhxjxYUaIvhZKkk%7Ctkp%3ABFBMxI-P8oRjThe resistor could anyway get a bit larger form factor for more power handling. 2 x 1 ohm + some 100 ohm to trim may also be an option.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: December 02, 2023, 03:19:38 am
content: Also lots of .24 ohm resistors on ebay.

author: BradC
author_rank: Super Contributor
timestamp: December 02, 2023, 04:07:53 am
content: There are 9 different 470mΩ 1W resistors listed on digikey for between $0.42 and $1.52 USD. That's within the tolerance of a 480mΩ 5% resistor. Grab the 1% 470 for $1.52 and you're golden.Edit :If my calcs are correct, using 470mΩ vs 480mΩ will make your low current ranges read low by :50u : 0.4 PPM5m : 198 PPM50m : 2,008 PPM (0.2%)500m: 20,833 PPM (2.8%)I'd wager the meter movement isn't that accurate.

author: aleeeeaaa
author_rank: Newbie
timestamp: December 03, 2023, 02:15:21 pm
content: Ordered the 470 mohm resistor. Thanks for all the help everyone