Digital volt/amp meters driving me INSANE with display readings - Page 1
Forum section: electronics / beginners

author: neeboy74
author_rank: Newbie
timestamp: November 29, 2024, 08:11:02 pm
content: Hello to all:I am trying to learn about electronics on the side. I have several of these digital volt/amp meters, and they all insist on displaying 00.0, instead of 0.00; I can't find ANY meters for sale in this format that are advertised to acutally do thisI've also read in at least one place that "if current is below 10 amps, no shunt needed"...my pics say otherwise, ummm, why?The other two pics show a strip of LED's attached, one as-is and one with the amp reading adjusted as far as it will go (still not accurate)Any informed comments are welcomed...I'm already resigned to probably buying/trying a different vendor's meter in the future, but I've designed and 3d-printed special housings specifically for these meters, so to get actual use out of them is still a desired goal.

author: Eraldo
author_rank: Regular Contributor
timestamp: November 29, 2024, 08:57:34 pm
content: Yeah these things dont go beyond 3 digit precision and they're too simple to have auto ranging. Maybe there are revisions of this device that can do that but i haven't seen them. If you want a better voltage meter then you can get one with 4 digits, but it shows voltage only.Also about the shunt, these devices have a small one in the pcb for a current of up to 10A. If you need higher current you need to connect the second shunt which has a lower resistance and so it can handle more current. I don't believe they have a way to tell which shunt it's using so you will need to make some conversions in your head to know the correct current. Assuming the resistance of the big shunt is 1/10, you would need to multiply the current shown in the display by ten.

author: Poroit
author_rank: Frequent Contributor
timestamp: November 30, 2024, 03:06:48 am
content: G'day neeboy74,DC Shunts generate millivolts.I would suggest that the statement, no shunt needed below 10A means that there is a model of meter available with an internal shunt.Higher value current shunts are normally external so you don't heat the internal of the meter.

author: iMo
author_rank: Super Contributor
timestamp: November 30, 2024, 08:43:35 am
content: Your meter is 100V/50A (or 100A), it seems.You always need that external shunt to measure those currents, sure.Your unit may not work properly without the external shunt wired (there is none shunt inside the meter).BTW., always post the link or schematics (if you need an advice)..PS: here is something similar -https://www.ebay.co.uk/itm/154887729827?_trksid=p2332490.c101875.m1851&itmprp=cksum%3A15488772982757844e02cda44fa7b92410f19b3147b8%7Cenc%3AAQAJAAABQNthdh9o32sOfKme0krmx3yc5y0DRWWwwpiraCEsA5rOcanQjqu91drTeDElZLF31uaWQXaQ2pNTl5IMyA1OfooQwqEcJUvtG9LvKPKHgcRzphx12iPvBSva61o%252BMhuWL8LzUK7lVbwH2earXqHKIyj3QoJd5WOl1SvvF9IaefrPOxsZBjPpB7oEyVjI%252FLO62nqC82RJ7SD%252BIyMz2mH4YvbRvPTPDa5olqEr7BBzjTvspK5pdOES0AnEkJUzDBjrjREQHbP5sSRpW44bQT%252FwwoGYBb1HGKlYENt8VUTJEbF2OqX%252BOSnVbPWcTor73bPhAPA%252FPUuJPyg3VW%252FIMLAQWIFqEUOar6oucgk7MssX1HFCYPdO%252BcNRkQSjPt3lZw6zKmTM1hJsRodLC9K3O5Rp2utue%252BEFYZhUCls4LaVjQaI6%7Campid%3APL_CLK%7Cclp%3A2332490&itmmeta=01JDY3HEJ2C5EWB81S3H4PDPGJMind the wiring schematics there..

author: Eraldo
author_rank: Regular Contributor
timestamp: November 30, 2024, 06:55:54 pm
content: Just a reply to clarify my previous post. It seems that your device is the 100A version and they do not have an internal shunt. My bad.I assumed that they were selling the big shunt as an extra range for the 10A version but the ones supporting only 10 Amps are not compatible with it and the 100A ones do not include that pcb shunt.Anyways the big shunt is necessary and the voltage resolution will not change (It's fixed xx.x). Another caveat about the input voltage is that this device can measure 100V only when the yellow wire (with the black as ground) is being powered by a 4-30V external voltage.But i doubt you'll be using it with voltages higher than 24V.